Carlos Martinez, MD

Central nervous system (CNS) lymphoma can be classified into 2 categories: primary CNS lymphoma (PCNSL), which includes disease limited to brain, eyes, spinal cord; and leptomeninges without coexisting or previous systemic lymphoma. Secondary CNS lymphoma (SCNSL) is essentially metastatic disease from a systemic primary site.¹ The focus of this case presentation is PCNSL, with an emphasis on imaging characteristics and differential diagnosis.

The median age at diagnosis for PCNSL is 65 years, and the overall incidence has been decreasing since the mid-1990s, likely related to the increased use of highly-active antiretroviral therapy (HAART) in patients with AIDS.^2,3 Although overall incidence has decreased, incidence in the elderly population has increased.⁴ Historically, PCNSL has been considered an AIDS-defining illness.⁵ These patients, among other immunocompromised patients, such as those on chronic immunosuppressive therapy, are at a higher risk for developing the malignancy.⁶

Clinical presentation varies because of the location of CNS involvement and may present with headache, mood or personality disturbances, or focal neurologic deficits. Seizures are less likely due to the tendency of PCNSL to spare gray matter. Initial workup generally includes a head computed tomography (CT) scan, as well as a contrast-enhanced magnetic resonance image (MRI), which may help direct clinicians to the appropriate diagnosis. However, there is significant overlap between the imaging characteristics of PCNSL and numerous other disease processes, including glioblastoma and demyelination. The imaging characteristics of PCNSL are considerably different depending on the patient’s immune status.⁷

This case illustrates a rare presentation of PCNSL in an immunocompetent patient whose MRI characteristics were seemingly more consistent with those seen in patients with immunodeficiency. The main differential diagnoses and key imaging characteristics, which may help obtain accurate diagnosis, will be discussed.

Case Presentation

A 72-year-old male veteran presented with a 2-month history of subjective weakness in his upper and lower extremities progressing to multiple falls at home. He had no significant medical history other than a thymectomy at age 15 for an enlarged thymus, which per patient report, was benign. An initial laboratory test that included vitamin B₁₂, folate, thyroid-stimulating hormone, complete blood cell count, and comprehensive metabolic panel, were unremarkable, with a white blood cell count of 8.5 K/uL. The initial neurologic evaluation did not show any focal neurologic deficits; however, during the initial hospital stay, the patient developed increasing lower extremity weakness on examination. A noncontrast CT head scan showed extensive nonspecific hypodensities within the periventricular white matter (Figure 1). A contrast-enhanced MRI showed enhancing lesions involving the corpus callosum, left cerebral peduncle, and right temporal lobe (Figures 2, 3, and 4). These lesions also exhibited significant restricted diffusion and a mild amount of surrounding vasogenic edema. The working diagnosis after the MRI included primary CNS lymphoma, multifocal glioblastoma, and tumefactive demyelinating disease. The patient was started on IV steroids and transferred for neurosurgical evaluation and biopsy at an outside hospital. The frontal lesion was biopsied, and the initial frozen section was consistent with lymphoma; a bone marrow biopsy was negative. The workup for immunodeficiency was unremarkable. Pathology revealed high-grade B-cell lymphoma, and the patient began a chemotherapy regimen.

Discussion

The workup of altered mental status, focal neurologic deficits, headaches, or other neurologic conditions often begins with a noncontrast CT scan. On CT, PCNSL generally appears isodense to hyperdense to gray matter, but appearance is variable. The often hyperdense appearance is attributable to the hypercellular nature of lymphoma. Many times, as in this case, CT may show only vague hypodensities, some of which may be associated with surrounding edema. This presentation is nonspecific and may be seen with advancing age due to changes of chronic microvascular ischemia as well as demyelination, other malignancies, and several other disease processes, both benign and malignant. After the initial CT scan, further workup requires evaluation with MRI. PCNSL exhibits restricted diffusion and variable signal intensity on T2-weighted imaging.

PCNSL is frequently centrally located within the periventricular white matter, often within the frontal lobe but can involve other lobes, the basal ganglia, brainstem, cerebellum, or less likely, the spinal canal.⁷ Contrary to primary CNS disease, secondary lymphoma within the CNS has been described classically as affecting a leptomeningeal (pia and arachnoid mater) distribution two-thirds of the time, with parenchymal involvement occurring in the other one-third of patients. A recent study by Malikova and colleagues found parenchymal involvement may be much more common than previously thought.¹ Leptomeningeal spread of disease often involves the cranial nerves, subependymal regions, spinal cord, or spinal nerve roots. Dural involvement in primary or secondary lymphoma is rare.

PCNSL nearly always shows enhancement. Linear enhancement along perivascular spaces is highly characteristic of PCNSL. The typical appearance of PCNSL associated with immunodeficiency varies from that seen in an otherwise immunocompetent patient. Patients with immunodeficiency usually have multifocal involvement, central necrosis leading to a ring enhancement appearance, and have more propensity for spontaneous hemorrhage.⁷ Immunocompetent patients are less likely to present with multifocal disease and rarely show ring enhancement. Also, spontaneous hemorrhage is rare in immunocompetent patients. In our case, extensive multifocal involvement was present, whereas typically immunocompetent patients will present with a solitary homogeneously enhancing parenchymal mass.

The primary differential for PCNSL includes malignant glioma, tumefactive multiple sclerosis, metastatic disease, and in an immunocompromised patient, toxoplasmosis. The degree of associated vasogenic edema and mass effect is generally lower in PCNSL than that of malignant gliomas and metastasis. Also, PCNSL tends to spare the cerebral cortex.⁸

Classically, PCNSL, malignant gliomas, and demyelinating disease have been considered the main differential for lesions that cross midline and involve both cerebral hemispheres. Lymphoma generally exhibits more restricted diffusion than malignant gliomas and metastasis, attributable to the highly cellular nature of lymphoma.⁷ Tumefactive multiple sclerosis is associated with relatively minimal mass effect for lesion size and exhibits less restricted diffusion values when compared to high grade gliomas and PCNSL. One fairly specific finding for tumefactive demyelinating lesions is incomplete rim enhancement.⁹ Unfortunately, an MRI is not reliable in differentiating these entities, and biopsy is required for definitive diagnosis. Many advancing imaging modalities may help provide the correct diagnosis of PCNSL, including diffusion-weighted and apparent diffusion coefficient imaging, diffusion tensor imaging, MR spectroscopy and PET imaging.⁷

Conclusion

With the increasing use of HAART, the paradigm of PCNSL is shifting toward one predominantly affecting immunocompetent patients. PCNSL should be considered in any patient with multiple enhancing CNS lesions, regardless of immune status. Several key imaging characteristics may help differentiate PCNSL and other disease processes; however, at this time, biopsy is recommended for definitive diagnosis.

Central nervous system (CNS) lymphoma can be classified into 2 categories: primary CNS lymphoma (PCNSL), which includes disease limited to brain, eyes, spinal cord; and leptomeninges without coexisting or previous systemic lymphoma. Secondary CNS lymphoma (SCNSL) is essentially metastatic disease from a systemic primary site.¹ The focus of this case presentation is PCNSL, with an emphasis on imaging characteristics and differential diagnosis.

The median age at diagnosis for PCNSL is 65 years, and the overall incidence has been decreasing since the mid-1990s, likely related to the increased use of highly-active antiretroviral therapy (HAART) in patients with AIDS.^2,3 Although overall incidence has decreased, incidence in the elderly population has increased.⁴ Historically, PCNSL has been considered an AIDS-defining illness.⁵ These patients, among other immunocompromised patients, such as those on chronic immunosuppressive therapy, are at a higher risk for developing the malignancy.⁶

Clinical presentation varies because of the location of CNS involvement and may present with headache, mood or personality disturbances, or focal neurologic deficits. Seizures are less likely due to the tendency of PCNSL to spare gray matter. Initial workup generally includes a head computed tomography (CT) scan, as well as a contrast-enhanced magnetic resonance image (MRI), which may help direct clinicians to the appropriate diagnosis. However, there is significant overlap between the imaging characteristics of PCNSL and numerous other disease processes, including glioblastoma and demyelination. The imaging characteristics of PCNSL are considerably different depending on the patient’s immune status.⁷

This case illustrates a rare presentation of PCNSL in an immunocompetent patient whose MRI characteristics were seemingly more consistent with those seen in patients with immunodeficiency. The main differential diagnoses and key imaging characteristics, which may help obtain accurate diagnosis, will be discussed.

Case Presentation

A 72-year-old male veteran presented with a 2-month history of subjective weakness in his upper and lower extremities progressing to multiple falls at home. He had no significant medical history other than a thymectomy at age 15 for an enlarged thymus, which per patient report, was benign. An initial laboratory test that included vitamin B₁₂, folate, thyroid-stimulating hormone, complete blood cell count, and comprehensive metabolic panel, were unremarkable, with a white blood cell count of 8.5 K/uL. The initial neurologic evaluation did not show any focal neurologic deficits; however, during the initial hospital stay, the patient developed increasing lower extremity weakness on examination. A noncontrast CT head scan showed extensive nonspecific hypodensities within the periventricular white matter (Figure 1). A contrast-enhanced MRI showed enhancing lesions involving the corpus callosum, left cerebral peduncle, and right temporal lobe (Figures 2, 3, and 4). These lesions also exhibited significant restricted diffusion and a mild amount of surrounding vasogenic edema. The working diagnosis after the MRI included primary CNS lymphoma, multifocal glioblastoma, and tumefactive demyelinating disease. The patient was started on IV steroids and transferred for neurosurgical evaluation and biopsy at an outside hospital. The frontal lesion was biopsied, and the initial frozen section was consistent with lymphoma; a bone marrow biopsy was negative. The workup for immunodeficiency was unremarkable. Pathology revealed high-grade B-cell lymphoma, and the patient began a chemotherapy regimen.

Discussion

The workup of altered mental status, focal neurologic deficits, headaches, or other neurologic conditions often begins with a noncontrast CT scan. On CT, PCNSL generally appears isodense to hyperdense to gray matter, but appearance is variable. The often hyperdense appearance is attributable to the hypercellular nature of lymphoma. Many times, as in this case, CT may show only vague hypodensities, some of which may be associated with surrounding edema. This presentation is nonspecific and may be seen with advancing age due to changes of chronic microvascular ischemia as well as demyelination, other malignancies, and several other disease processes, both benign and malignant. After the initial CT scan, further workup requires evaluation with MRI. PCNSL exhibits restricted diffusion and variable signal intensity on T2-weighted imaging.

PCNSL is frequently centrally located within the periventricular white matter, often within the frontal lobe but can involve other lobes, the basal ganglia, brainstem, cerebellum, or less likely, the spinal canal.⁷ Contrary to primary CNS disease, secondary lymphoma within the CNS has been described classically as affecting a leptomeningeal (pia and arachnoid mater) distribution two-thirds of the time, with parenchymal involvement occurring in the other one-third of patients. A recent study by Malikova and colleagues found parenchymal involvement may be much more common than previously thought.¹ Leptomeningeal spread of disease often involves the cranial nerves, subependymal regions, spinal cord, or spinal nerve roots. Dural involvement in primary or secondary lymphoma is rare.

PCNSL nearly always shows enhancement. Linear enhancement along perivascular spaces is highly characteristic of PCNSL. The typical appearance of PCNSL associated with immunodeficiency varies from that seen in an otherwise immunocompetent patient. Patients with immunodeficiency usually have multifocal involvement, central necrosis leading to a ring enhancement appearance, and have more propensity for spontaneous hemorrhage.⁷ Immunocompetent patients are less likely to present with multifocal disease and rarely show ring enhancement. Also, spontaneous hemorrhage is rare in immunocompetent patients. In our case, extensive multifocal involvement was present, whereas typically immunocompetent patients will present with a solitary homogeneously enhancing parenchymal mass.

The primary differential for PCNSL includes malignant glioma, tumefactive multiple sclerosis, metastatic disease, and in an immunocompromised patient, toxoplasmosis. The degree of associated vasogenic edema and mass effect is generally lower in PCNSL than that of malignant gliomas and metastasis. Also, PCNSL tends to spare the cerebral cortex.⁸

Classically, PCNSL, malignant gliomas, and demyelinating disease have been considered the main differential for lesions that cross midline and involve both cerebral hemispheres. Lymphoma generally exhibits more restricted diffusion than malignant gliomas and metastasis, attributable to the highly cellular nature of lymphoma.⁷ Tumefactive multiple sclerosis is associated with relatively minimal mass effect for lesion size and exhibits less restricted diffusion values when compared to high grade gliomas and PCNSL. One fairly specific finding for tumefactive demyelinating lesions is incomplete rim enhancement.⁹ Unfortunately, an MRI is not reliable in differentiating these entities, and biopsy is required for definitive diagnosis. Many advancing imaging modalities may help provide the correct diagnosis of PCNSL, including diffusion-weighted and apparent diffusion coefficient imaging, diffusion tensor imaging, MR spectroscopy and PET imaging.⁷

Conclusion

With the increasing use of HAART, the paradigm of PCNSL is shifting toward one predominantly affecting immunocompetent patients. PCNSL should be considered in any patient with multiple enhancing CNS lesions, regardless of immune status. Several key imaging characteristics may help differentiate PCNSL and other disease processes; however, at this time, biopsy is recommended for definitive diagnosis.

Central nervous system (CNS) lymphoma can be classified into 2 categories: primary CNS lymphoma (PCNSL), which includes disease limited to brain, eyes, spinal cord; and leptomeninges without coexisting or previous systemic lymphoma. Secondary CNS lymphoma (SCNSL) is essentially metastatic disease from a systemic primary site.¹ The focus of this case presentation is PCNSL, with an emphasis on imaging characteristics and differential diagnosis.

The median age at diagnosis for PCNSL is 65 years, and the overall incidence has been decreasing since the mid-1990s, likely related to the increased use of highly-active antiretroviral therapy (HAART) in patients with AIDS.^2,3 Although overall incidence has decreased, incidence in the elderly population has increased.⁴ Historically, PCNSL has been considered an AIDS-defining illness.⁵ These patients, among other immunocompromised patients, such as those on chronic immunosuppressive therapy, are at a higher risk for developing the malignancy.⁶

Clinical presentation varies because of the location of CNS involvement and may present with headache, mood or personality disturbances, or focal neurologic deficits. Seizures are less likely due to the tendency of PCNSL to spare gray matter. Initial workup generally includes a head computed tomography (CT) scan, as well as a contrast-enhanced magnetic resonance image (MRI), which may help direct clinicians to the appropriate diagnosis. However, there is significant overlap between the imaging characteristics of PCNSL and numerous other disease processes, including glioblastoma and demyelination. The imaging characteristics of PCNSL are considerably different depending on the patient’s immune status.⁷

This case illustrates a rare presentation of PCNSL in an immunocompetent patient whose MRI characteristics were seemingly more consistent with those seen in patients with immunodeficiency. The main differential diagnoses and key imaging characteristics, which may help obtain accurate diagnosis, will be discussed.

Case Presentation

A 72-year-old male veteran presented with a 2-month history of subjective weakness in his upper and lower extremities progressing to multiple falls at home. He had no significant medical history other than a thymectomy at age 15 for an enlarged thymus, which per patient report, was benign. An initial laboratory test that included vitamin B₁₂, folate, thyroid-stimulating hormone, complete blood cell count, and comprehensive metabolic panel, were unremarkable, with a white blood cell count of 8.5 K/uL. The initial neurologic evaluation did not show any focal neurologic deficits; however, during the initial hospital stay, the patient developed increasing lower extremity weakness on examination. A noncontrast CT head scan showed extensive nonspecific hypodensities within the periventricular white matter (Figure 1). A contrast-enhanced MRI showed enhancing lesions involving the corpus callosum, left cerebral peduncle, and right temporal lobe (Figures 2, 3, and 4). These lesions also exhibited significant restricted diffusion and a mild amount of surrounding vasogenic edema. The working diagnosis after the MRI included primary CNS lymphoma, multifocal glioblastoma, and tumefactive demyelinating disease. The patient was started on IV steroids and transferred for neurosurgical evaluation and biopsy at an outside hospital. The frontal lesion was biopsied, and the initial frozen section was consistent with lymphoma; a bone marrow biopsy was negative. The workup for immunodeficiency was unremarkable. Pathology revealed high-grade B-cell lymphoma, and the patient began a chemotherapy regimen.

Discussion

The workup of altered mental status, focal neurologic deficits, headaches, or other neurologic conditions often begins with a noncontrast CT scan. On CT, PCNSL generally appears isodense to hyperdense to gray matter, but appearance is variable. The often hyperdense appearance is attributable to the hypercellular nature of lymphoma. Many times, as in this case, CT may show only vague hypodensities, some of which may be associated with surrounding edema. This presentation is nonspecific and may be seen with advancing age due to changes of chronic microvascular ischemia as well as demyelination, other malignancies, and several other disease processes, both benign and malignant. After the initial CT scan, further workup requires evaluation with MRI. PCNSL exhibits restricted diffusion and variable signal intensity on T2-weighted imaging.

PCNSL is frequently centrally located within the periventricular white matter, often within the frontal lobe but can involve other lobes, the basal ganglia, brainstem, cerebellum, or less likely, the spinal canal.⁷ Contrary to primary CNS disease, secondary lymphoma within the CNS has been described classically as affecting a leptomeningeal (pia and arachnoid mater) distribution two-thirds of the time, with parenchymal involvement occurring in the other one-third of patients. A recent study by Malikova and colleagues found parenchymal involvement may be much more common than previously thought.¹ Leptomeningeal spread of disease often involves the cranial nerves, subependymal regions, spinal cord, or spinal nerve roots. Dural involvement in primary or secondary lymphoma is rare.

PCNSL nearly always shows enhancement. Linear enhancement along perivascular spaces is highly characteristic of PCNSL. The typical appearance of PCNSL associated with immunodeficiency varies from that seen in an otherwise immunocompetent patient. Patients with immunodeficiency usually have multifocal involvement, central necrosis leading to a ring enhancement appearance, and have more propensity for spontaneous hemorrhage.⁷ Immunocompetent patients are less likely to present with multifocal disease and rarely show ring enhancement. Also, spontaneous hemorrhage is rare in immunocompetent patients. In our case, extensive multifocal involvement was present, whereas typically immunocompetent patients will present with a solitary homogeneously enhancing parenchymal mass.

The primary differential for PCNSL includes malignant glioma, tumefactive multiple sclerosis, metastatic disease, and in an immunocompromised patient, toxoplasmosis. The degree of associated vasogenic edema and mass effect is generally lower in PCNSL than that of malignant gliomas and metastasis. Also, PCNSL tends to spare the cerebral cortex.⁸

Classically, PCNSL, malignant gliomas, and demyelinating disease have been considered the main differential for lesions that cross midline and involve both cerebral hemispheres. Lymphoma generally exhibits more restricted diffusion than malignant gliomas and metastasis, attributable to the highly cellular nature of lymphoma.⁷ Tumefactive multiple sclerosis is associated with relatively minimal mass effect for lesion size and exhibits less restricted diffusion values when compared to high grade gliomas and PCNSL. One fairly specific finding for tumefactive demyelinating lesions is incomplete rim enhancement.⁹ Unfortunately, an MRI is not reliable in differentiating these entities, and biopsy is required for definitive diagnosis. Many advancing imaging modalities may help provide the correct diagnosis of PCNSL, including diffusion-weighted and apparent diffusion coefficient imaging, diffusion tensor imaging, MR spectroscopy and PET imaging.⁷

Conclusion

With the increasing use of HAART, the paradigm of PCNSL is shifting toward one predominantly affecting immunocompetent patients. PCNSL should be considered in any patient with multiple enhancing CNS lesions, regardless of immune status. Several key imaging characteristics may help differentiate PCNSL and other disease processes; however, at this time, biopsy is recommended for definitive diagnosis.

Altered mental status (AMS) is a common presentation to the emergency department (ED) for older patients and is often due to underlying drug-associated adverse effects (AEs), medical or psychiatric illness, or neurologic disease. EDs often have protocols for diagnosing and managing AMS to assess the underlying etiology. A formal assessment with a full history and physical examination is paramount to diagnosing the cause of AMS.

Oral metronidazole is a commonly used antibiotic for anaerobic bacterial infections and Clostridium difficile-associated diarrhea and colitis.¹Metronidazole produces cytotoxic intermediates that cause DNA strand breakage and destabilization, resulting in bactericidal activity in host cells.²Common AEs include gastrointestinal symptoms such as nausea, vomiting, and diarrhea; less common AEs can involve the nervous system and include seizures, peripheral neuropathy, dizziness, ataxia, and encephalopathy.^3,4A pattern of magnetic resonance image (MRI) abnormalities typically located at the cerebellar dentate nucleus midbrain, dorsal pons, medulla, and splenium of the corpus callosum have been associated with metronidazole usage.⁵

Hyperbaric oxygen therapy (HBOT) is a treatment modality used as the primary therapy for decompression sickness, arterial gas embolism, and carbon monoxide poisoning. HBOT is used as adjuvant therapy for osteonecrosis caused by radiation or bisphosphonate use.^6,7 HBOT increases the partial pressure of oxygen in plasma and increases the amount of oxygen delivered to tissues throughout the body.⁸Hyperoxia, defined as an elevated partial pressure of oxygen leading to excess oxygenation to tissues and organs, increases production of reactive oxygen and nitrogen species, which are signaling factors in a variety of pathways that stimulate angiogenesis.⁸ AEs of HBOT include barotrauma-related injuries and oxygen toxicity, such as respiratory distress or central nervous system (CNS) symptoms.⁹ Severe CNS AEs occur in 1% to 2% of patients undergoing therapy and manifest as generalized tonic-clonic seizures, typically in patients with preexisting neurologic disorders, brain injury, or lowered seizure threshold.^7,8,10 There have been no documented incidences of HBOT inducing acute encephalopathy.

Case Presentation

A 63-year-old male smoker with no history of alcohol use presented to the ED with an acute onset of lightheadedness, confusion, and poor coordination following his second HBOT for radiation-induced osteonecrosis of the mandible. The patient reported chronic, slowly progressive pain and numbness of the feet that began 4 years earlier. He noted marked worsening of pain and difficulty standing and walking 3 to 4 months prior to presentation.

Ten years prior, the patient was diagnosed with cancer of the right tonsil. A tonsillectomy with wide margins was performed, followed by 35 rounds of radiation treatment and 2 rounds of chemotherapy with cisplatin.

In May 2017, the patient presented with a lump in the right cheek that was diagnosed as osteonecrosis of the mandible. An oral surgeon prescribed metronidazole 500 mg qid and amoxicillin 500 mg tid. The patient was adherent until presentation in November 2017. Following lack of improvement of the osteonecrosis from antibiotic therapy, oral surgery was planned, and the patient was referred for HBOT with a planned 20 HBOT preoperative treatments and 10 postoperative treatments.

Following his first 2-hour HBOT treatment on November 13, 2017, the patient complained of light-headedness, confusion, and incoordination. While driving on a familiar route to his home, he collided with a tree that was 6 feet from the curb. The patient attempted to drive another vehicle later that day, resulting in a second motor vehicle accident. There was no significant injury reported in either accident.

His partner described the patient’s episode of disorientation lasting 6 to 8 hours, during which he “looked drunk” and was unable to sit in a chair without falling. The following morning, the patient had improved mental status but had not returned to baseline. His second HBOT treatment took place that day, and again, the patient acutely experienced light-headedness and confusion following completion. Therapy was suspended, and the patient was referred to the ED for further evaluation. Mild facial asymmetry without weakness, decreased sensation from toes to knees bilaterally, and absent Achilles reflexes bilaterally were found on neurologic examination. He exhibited past-pointing on finger-to-nose testing bilaterally. He was able to ambulate independently, but he could not perform tandem gait.

An MRI of the brain showed abnormal T2 hyperintensity found bilaterally at the dentate nuclei and inferior colliculi. The splenium of the corpus callosum also showed mild involvement with hyperintense lesions. Laboratory tests of the patient’s complete blood count; comprehensive metabolic panel; vitamins B₁, B₆, B₁₂; and folic acid levels had no notable abnormalities and were within normal limits.

Metronidazole and HBOT therapy were discontinued, and all of the patient’s symptoms resolved within 2 weeks. A repeat examination and MRI performed 1 month later showed resolution of all the patient’s clinical findings and MRI abnormalities. HBOT was resumed without the recurrence of previously described symptoms.

Discussion

This patient’s encephalopathic symptoms correlate temporally with the onset of HBOT. There is no medical literature suggesting a relationship between HBOT and encephalopathic symptoms with MRI abnormalities, and in fact, some studies suggest HBOT as a treatment for hypoxic-ischemic encephalopathy in neonates.¹¹ This led us to believe that the HBOT may have exacerbated some underlying condition, evidenced by the specific MRI findings of T2 fluid-attenuated inversion recovery (FLAIR) hyperintensities in the dentate nuclei and inferior colliculi (Figures 1 and 2). 

Differential diagnoses for T2 hyperintense lesions in the dentate nuclei include metronidazole toxicity, acute Wernicke encephalopathy (WE), and methyl bromide intoxication. Diseases that would have presented in infancy with similar MRI findings (Canavan disease, maple-syrup urine disease, and glutaric aciduria type 1) were not considered plausible.^12-14 

Despite his denial of alcohol use, the patient was at risk for malnutrition secondary to his mandibular lesion and difficulty eating. Clinically, he presented with episodes of confusion and ataxia, consistent with 2 of the classic triad of symptoms of WE (no ocular abnormalities noted on exam). Typical MRI findings in WE include signal intensity alterations (including T2 hyperintensities) in the medial thalami, mammillary bodies, collicular bodies, and periaqueductal and periventricular regions.^14,15 Atypical MRI findings in WE include symmetric signal intensity changes in the cerebellum, dentate nuclei, caudate nuclei, red nuclei, cranial nerve nuclei, and splenium.¹⁴ Of note, atypical MRI findings were more common in patients without alcohol use disorders and WE, and typical MRI findings were more common in patients with alcohol use disorders.¹⁴ However, this patient’s report of no alcohol use and the serum thiamine level being within normal limits (173 nmol/L; range 78-185 nmol/L) made acute WE less likely than metronidonazale-induced encephalopathy (MIE).

The most common neurologic AE of metronidazole is distal symmetric sensory polyneuropathy, which also can have motor or autonomic features.^16,17 While our patient had a history of peripheral neuropathy, he noted marked worsening of foot pain 3 months after initiating metronidazole therapy. A potential mechanism involves metronidazole or its cytotoxic intermediates binding neuronal ribonucleic acids, thus inhibiting protein synthesis and resulting in degenerative neuronal changes and reversible axonal swelling (as opposed to the DNA interference attributed to the drug’s mechanism of bactericidal action).¹⁸ Neuropathies may result from prolonged high-dose metronidazole therapy (cumulative dose > 42 g),³ but they also have been seen in short-term use of high dosages.¹⁷

CNS AEs are much rarer and are thought to be associated with metronidazole’s ability to cross the blood-brain barrier. These patients present as a toxic encephalopathy with cerebellar dysfunction (dysarthria, ataxia) as the most common presentation, followed by AMS and seizures.⁴ Our patient presented with acute confusion and ataxia. Animal studies suggest that γ-aminobutyric acid (GABA) receptor modulation in the cerebellar and vestibular systems may contribute to this neurotoxicity, but no definitive mechanism of injury has been found.¹⁹

On MRI, MIE most commonly presents with hyperintense lesions in the bilateral cerebellar dentate nucleus on T2-weighted and FLAIR images.^5,20 The midbrain, dorsal pons, medulla, and corpus callosum also can show increased signal intensity.⁵ This AE does not seem to be dose- or duration-dependent, and most cases report complete or partial resolution of symptoms following discontinuation of the drug, though this is not absolute.^4,13,21 The patient’s MRI findings were highly consistent with MIE (Figure 2).

Conclusion

This patient’s highly specific MRI findings, neurologic examination consistent with confusion, ataxia, length-dependent sensory neuropathy, and 360-g cumulative dose of metronidazole over the previous 6 months suggest he experienced MIE. The mechanism of how HBOT precipitated the patient’s altered mental status, incoordination, and worsening of peripheral neuropathy is unknown. Although encephalopathy with MRI abnormalities as described is not a reported AE of HBOT, it may be unrecognized. It is possible that without HBOT the patient would have remained asymptomatic apart from his peripheral neuropathy.

We propose HBOT may exacerbate or increase the risk of a patient developing MIE. Our patient was able to safely resume HBOT after metronidazole was discontinued, suggesting that the combination was the causation for the development of encephalopathy. We do not believe any similar cases have been reported.

Altered mental status (AMS) is a common presentation to the emergency department (ED) for older patients and is often due to underlying drug-associated adverse effects (AEs), medical or psychiatric illness, or neurologic disease. EDs often have protocols for diagnosing and managing AMS to assess the underlying etiology. A formal assessment with a full history and physical examination is paramount to diagnosing the cause of AMS.

Oral metronidazole is a commonly used antibiotic for anaerobic bacterial infections and Clostridium difficile-associated diarrhea and colitis.¹Metronidazole produces cytotoxic intermediates that cause DNA strand breakage and destabilization, resulting in bactericidal activity in host cells.²Common AEs include gastrointestinal symptoms such as nausea, vomiting, and diarrhea; less common AEs can involve the nervous system and include seizures, peripheral neuropathy, dizziness, ataxia, and encephalopathy.^3,4A pattern of magnetic resonance image (MRI) abnormalities typically located at the cerebellar dentate nucleus midbrain, dorsal pons, medulla, and splenium of the corpus callosum have been associated with metronidazole usage.⁵

Hyperbaric oxygen therapy (HBOT) is a treatment modality used as the primary therapy for decompression sickness, arterial gas embolism, and carbon monoxide poisoning. HBOT is used as adjuvant therapy for osteonecrosis caused by radiation or bisphosphonate use.^6,7 HBOT increases the partial pressure of oxygen in plasma and increases the amount of oxygen delivered to tissues throughout the body.⁸Hyperoxia, defined as an elevated partial pressure of oxygen leading to excess oxygenation to tissues and organs, increases production of reactive oxygen and nitrogen species, which are signaling factors in a variety of pathways that stimulate angiogenesis.⁸ AEs of HBOT include barotrauma-related injuries and oxygen toxicity, such as respiratory distress or central nervous system (CNS) symptoms.⁹ Severe CNS AEs occur in 1% to 2% of patients undergoing therapy and manifest as generalized tonic-clonic seizures, typically in patients with preexisting neurologic disorders, brain injury, or lowered seizure threshold.^7,8,10 There have been no documented incidences of HBOT inducing acute encephalopathy.

Case Presentation

A 63-year-old male smoker with no history of alcohol use presented to the ED with an acute onset of lightheadedness, confusion, and poor coordination following his second HBOT for radiation-induced osteonecrosis of the mandible. The patient reported chronic, slowly progressive pain and numbness of the feet that began 4 years earlier. He noted marked worsening of pain and difficulty standing and walking 3 to 4 months prior to presentation.

Ten years prior, the patient was diagnosed with cancer of the right tonsil. A tonsillectomy with wide margins was performed, followed by 35 rounds of radiation treatment and 2 rounds of chemotherapy with cisplatin.

In May 2017, the patient presented with a lump in the right cheek that was diagnosed as osteonecrosis of the mandible. An oral surgeon prescribed metronidazole 500 mg qid and amoxicillin 500 mg tid. The patient was adherent until presentation in November 2017. Following lack of improvement of the osteonecrosis from antibiotic therapy, oral surgery was planned, and the patient was referred for HBOT with a planned 20 HBOT preoperative treatments and 10 postoperative treatments.

Following his first 2-hour HBOT treatment on November 13, 2017, the patient complained of light-headedness, confusion, and incoordination. While driving on a familiar route to his home, he collided with a tree that was 6 feet from the curb. The patient attempted to drive another vehicle later that day, resulting in a second motor vehicle accident. There was no significant injury reported in either accident.

His partner described the patient’s episode of disorientation lasting 6 to 8 hours, during which he “looked drunk” and was unable to sit in a chair without falling. The following morning, the patient had improved mental status but had not returned to baseline. His second HBOT treatment took place that day, and again, the patient acutely experienced light-headedness and confusion following completion. Therapy was suspended, and the patient was referred to the ED for further evaluation. Mild facial asymmetry without weakness, decreased sensation from toes to knees bilaterally, and absent Achilles reflexes bilaterally were found on neurologic examination. He exhibited past-pointing on finger-to-nose testing bilaterally. He was able to ambulate independently, but he could not perform tandem gait.

An MRI of the brain showed abnormal T2 hyperintensity found bilaterally at the dentate nuclei and inferior colliculi. The splenium of the corpus callosum also showed mild involvement with hyperintense lesions. Laboratory tests of the patient’s complete blood count; comprehensive metabolic panel; vitamins B₁, B₆, B₁₂; and folic acid levels had no notable abnormalities and were within normal limits.

Metronidazole and HBOT therapy were discontinued, and all of the patient’s symptoms resolved within 2 weeks. A repeat examination and MRI performed 1 month later showed resolution of all the patient’s clinical findings and MRI abnormalities. HBOT was resumed without the recurrence of previously described symptoms.

Discussion

This patient’s encephalopathic symptoms correlate temporally with the onset of HBOT. There is no medical literature suggesting a relationship between HBOT and encephalopathic symptoms with MRI abnormalities, and in fact, some studies suggest HBOT as a treatment for hypoxic-ischemic encephalopathy in neonates.¹¹ This led us to believe that the HBOT may have exacerbated some underlying condition, evidenced by the specific MRI findings of T2 fluid-attenuated inversion recovery (FLAIR) hyperintensities in the dentate nuclei and inferior colliculi (Figures 1 and 2). 

Differential diagnoses for T2 hyperintense lesions in the dentate nuclei include metronidazole toxicity, acute Wernicke encephalopathy (WE), and methyl bromide intoxication. Diseases that would have presented in infancy with similar MRI findings (Canavan disease, maple-syrup urine disease, and glutaric aciduria type 1) were not considered plausible.^12-14 

Despite his denial of alcohol use, the patient was at risk for malnutrition secondary to his mandibular lesion and difficulty eating. Clinically, he presented with episodes of confusion and ataxia, consistent with 2 of the classic triad of symptoms of WE (no ocular abnormalities noted on exam). Typical MRI findings in WE include signal intensity alterations (including T2 hyperintensities) in the medial thalami, mammillary bodies, collicular bodies, and periaqueductal and periventricular regions.^14,15 Atypical MRI findings in WE include symmetric signal intensity changes in the cerebellum, dentate nuclei, caudate nuclei, red nuclei, cranial nerve nuclei, and splenium.¹⁴ Of note, atypical MRI findings were more common in patients without alcohol use disorders and WE, and typical MRI findings were more common in patients with alcohol use disorders.¹⁴ However, this patient’s report of no alcohol use and the serum thiamine level being within normal limits (173 nmol/L; range 78-185 nmol/L) made acute WE less likely than metronidonazale-induced encephalopathy (MIE).

The most common neurologic AE of metronidazole is distal symmetric sensory polyneuropathy, which also can have motor or autonomic features.^16,17 While our patient had a history of peripheral neuropathy, he noted marked worsening of foot pain 3 months after initiating metronidazole therapy. A potential mechanism involves metronidazole or its cytotoxic intermediates binding neuronal ribonucleic acids, thus inhibiting protein synthesis and resulting in degenerative neuronal changes and reversible axonal swelling (as opposed to the DNA interference attributed to the drug’s mechanism of bactericidal action).¹⁸ Neuropathies may result from prolonged high-dose metronidazole therapy (cumulative dose > 42 g),³ but they also have been seen in short-term use of high dosages.¹⁷

CNS AEs are much rarer and are thought to be associated with metronidazole’s ability to cross the blood-brain barrier. These patients present as a toxic encephalopathy with cerebellar dysfunction (dysarthria, ataxia) as the most common presentation, followed by AMS and seizures.⁴ Our patient presented with acute confusion and ataxia. Animal studies suggest that γ-aminobutyric acid (GABA) receptor modulation in the cerebellar and vestibular systems may contribute to this neurotoxicity, but no definitive mechanism of injury has been found.¹⁹

On MRI, MIE most commonly presents with hyperintense lesions in the bilateral cerebellar dentate nucleus on T2-weighted and FLAIR images.^5,20 The midbrain, dorsal pons, medulla, and corpus callosum also can show increased signal intensity.⁵ This AE does not seem to be dose- or duration-dependent, and most cases report complete or partial resolution of symptoms following discontinuation of the drug, though this is not absolute.^4,13,21 The patient’s MRI findings were highly consistent with MIE (Figure 2).

Conclusion

This patient’s highly specific MRI findings, neurologic examination consistent with confusion, ataxia, length-dependent sensory neuropathy, and 360-g cumulative dose of metronidazole over the previous 6 months suggest he experienced MIE. The mechanism of how HBOT precipitated the patient’s altered mental status, incoordination, and worsening of peripheral neuropathy is unknown. Although encephalopathy with MRI abnormalities as described is not a reported AE of HBOT, it may be unrecognized. It is possible that without HBOT the patient would have remained asymptomatic apart from his peripheral neuropathy.

We propose HBOT may exacerbate or increase the risk of a patient developing MIE. Our patient was able to safely resume HBOT after metronidazole was discontinued, suggesting that the combination was the causation for the development of encephalopathy. We do not believe any similar cases have been reported.

Altered mental status (AMS) is a common presentation to the emergency department (ED) for older patients and is often due to underlying drug-associated adverse effects (AEs), medical or psychiatric illness, or neurologic disease. EDs often have protocols for diagnosing and managing AMS to assess the underlying etiology. A formal assessment with a full history and physical examination is paramount to diagnosing the cause of AMS.

Oral metronidazole is a commonly used antibiotic for anaerobic bacterial infections and Clostridium difficile-associated diarrhea and colitis.¹Metronidazole produces cytotoxic intermediates that cause DNA strand breakage and destabilization, resulting in bactericidal activity in host cells.²Common AEs include gastrointestinal symptoms such as nausea, vomiting, and diarrhea; less common AEs can involve the nervous system and include seizures, peripheral neuropathy, dizziness, ataxia, and encephalopathy.^3,4A pattern of magnetic resonance image (MRI) abnormalities typically located at the cerebellar dentate nucleus midbrain, dorsal pons, medulla, and splenium of the corpus callosum have been associated with metronidazole usage.⁵

Hyperbaric oxygen therapy (HBOT) is a treatment modality used as the primary therapy for decompression sickness, arterial gas embolism, and carbon monoxide poisoning. HBOT is used as adjuvant therapy for osteonecrosis caused by radiation or bisphosphonate use.^6,7 HBOT increases the partial pressure of oxygen in plasma and increases the amount of oxygen delivered to tissues throughout the body.⁸Hyperoxia, defined as an elevated partial pressure of oxygen leading to excess oxygenation to tissues and organs, increases production of reactive oxygen and nitrogen species, which are signaling factors in a variety of pathways that stimulate angiogenesis.⁸ AEs of HBOT include barotrauma-related injuries and oxygen toxicity, such as respiratory distress or central nervous system (CNS) symptoms.⁹ Severe CNS AEs occur in 1% to 2% of patients undergoing therapy and manifest as generalized tonic-clonic seizures, typically in patients with preexisting neurologic disorders, brain injury, or lowered seizure threshold.^7,8,10 There have been no documented incidences of HBOT inducing acute encephalopathy.

Case Presentation

A 63-year-old male smoker with no history of alcohol use presented to the ED with an acute onset of lightheadedness, confusion, and poor coordination following his second HBOT for radiation-induced osteonecrosis of the mandible. The patient reported chronic, slowly progressive pain and numbness of the feet that began 4 years earlier. He noted marked worsening of pain and difficulty standing and walking 3 to 4 months prior to presentation.

Ten years prior, the patient was diagnosed with cancer of the right tonsil. A tonsillectomy with wide margins was performed, followed by 35 rounds of radiation treatment and 2 rounds of chemotherapy with cisplatin.

In May 2017, the patient presented with a lump in the right cheek that was diagnosed as osteonecrosis of the mandible. An oral surgeon prescribed metronidazole 500 mg qid and amoxicillin 500 mg tid. The patient was adherent until presentation in November 2017. Following lack of improvement of the osteonecrosis from antibiotic therapy, oral surgery was planned, and the patient was referred for HBOT with a planned 20 HBOT preoperative treatments and 10 postoperative treatments.

Following his first 2-hour HBOT treatment on November 13, 2017, the patient complained of light-headedness, confusion, and incoordination. While driving on a familiar route to his home, he collided with a tree that was 6 feet from the curb. The patient attempted to drive another vehicle later that day, resulting in a second motor vehicle accident. There was no significant injury reported in either accident.

His partner described the patient’s episode of disorientation lasting 6 to 8 hours, during which he “looked drunk” and was unable to sit in a chair without falling. The following morning, the patient had improved mental status but had not returned to baseline. His second HBOT treatment took place that day, and again, the patient acutely experienced light-headedness and confusion following completion. Therapy was suspended, and the patient was referred to the ED for further evaluation. Mild facial asymmetry without weakness, decreased sensation from toes to knees bilaterally, and absent Achilles reflexes bilaterally were found on neurologic examination. He exhibited past-pointing on finger-to-nose testing bilaterally. He was able to ambulate independently, but he could not perform tandem gait.

An MRI of the brain showed abnormal T2 hyperintensity found bilaterally at the dentate nuclei and inferior colliculi. The splenium of the corpus callosum also showed mild involvement with hyperintense lesions. Laboratory tests of the patient’s complete blood count; comprehensive metabolic panel; vitamins B₁, B₆, B₁₂; and folic acid levels had no notable abnormalities and were within normal limits.

Metronidazole and HBOT therapy were discontinued, and all of the patient’s symptoms resolved within 2 weeks. A repeat examination and MRI performed 1 month later showed resolution of all the patient’s clinical findings and MRI abnormalities. HBOT was resumed without the recurrence of previously described symptoms.

Discussion

This patient’s encephalopathic symptoms correlate temporally with the onset of HBOT. There is no medical literature suggesting a relationship between HBOT and encephalopathic symptoms with MRI abnormalities, and in fact, some studies suggest HBOT as a treatment for hypoxic-ischemic encephalopathy in neonates.¹¹ This led us to believe that the HBOT may have exacerbated some underlying condition, evidenced by the specific MRI findings of T2 fluid-attenuated inversion recovery (FLAIR) hyperintensities in the dentate nuclei and inferior colliculi (Figures 1 and 2). 

Differential diagnoses for T2 hyperintense lesions in the dentate nuclei include metronidazole toxicity, acute Wernicke encephalopathy (WE), and methyl bromide intoxication. Diseases that would have presented in infancy with similar MRI findings (Canavan disease, maple-syrup urine disease, and glutaric aciduria type 1) were not considered plausible.^12-14 

Despite his denial of alcohol use, the patient was at risk for malnutrition secondary to his mandibular lesion and difficulty eating. Clinically, he presented with episodes of confusion and ataxia, consistent with 2 of the classic triad of symptoms of WE (no ocular abnormalities noted on exam). Typical MRI findings in WE include signal intensity alterations (including T2 hyperintensities) in the medial thalami, mammillary bodies, collicular bodies, and periaqueductal and periventricular regions.^14,15 Atypical MRI findings in WE include symmetric signal intensity changes in the cerebellum, dentate nuclei, caudate nuclei, red nuclei, cranial nerve nuclei, and splenium.¹⁴ Of note, atypical MRI findings were more common in patients without alcohol use disorders and WE, and typical MRI findings were more common in patients with alcohol use disorders.¹⁴ However, this patient’s report of no alcohol use and the serum thiamine level being within normal limits (173 nmol/L; range 78-185 nmol/L) made acute WE less likely than metronidonazale-induced encephalopathy (MIE).

The most common neurologic AE of metronidazole is distal symmetric sensory polyneuropathy, which also can have motor or autonomic features.^16,17 While our patient had a history of peripheral neuropathy, he noted marked worsening of foot pain 3 months after initiating metronidazole therapy. A potential mechanism involves metronidazole or its cytotoxic intermediates binding neuronal ribonucleic acids, thus inhibiting protein synthesis and resulting in degenerative neuronal changes and reversible axonal swelling (as opposed to the DNA interference attributed to the drug’s mechanism of bactericidal action).¹⁸ Neuropathies may result from prolonged high-dose metronidazole therapy (cumulative dose > 42 g),³ but they also have been seen in short-term use of high dosages.¹⁷

CNS AEs are much rarer and are thought to be associated with metronidazole’s ability to cross the blood-brain barrier. These patients present as a toxic encephalopathy with cerebellar dysfunction (dysarthria, ataxia) as the most common presentation, followed by AMS and seizures.⁴ Our patient presented with acute confusion and ataxia. Animal studies suggest that γ-aminobutyric acid (GABA) receptor modulation in the cerebellar and vestibular systems may contribute to this neurotoxicity, but no definitive mechanism of injury has been found.¹⁹

On MRI, MIE most commonly presents with hyperintense lesions in the bilateral cerebellar dentate nucleus on T2-weighted and FLAIR images.^5,20 The midbrain, dorsal pons, medulla, and corpus callosum also can show increased signal intensity.⁵ This AE does not seem to be dose- or duration-dependent, and most cases report complete or partial resolution of symptoms following discontinuation of the drug, though this is not absolute.^4,13,21 The patient’s MRI findings were highly consistent with MIE (Figure 2).

Conclusion

This patient’s highly specific MRI findings, neurologic examination consistent with confusion, ataxia, length-dependent sensory neuropathy, and 360-g cumulative dose of metronidazole over the previous 6 months suggest he experienced MIE. The mechanism of how HBOT precipitated the patient’s altered mental status, incoordination, and worsening of peripheral neuropathy is unknown. Although encephalopathy with MRI abnormalities as described is not a reported AE of HBOT, it may be unrecognized. It is possible that without HBOT the patient would have remained asymptomatic apart from his peripheral neuropathy.

We propose HBOT may exacerbate or increase the risk of a patient developing MIE. Our patient was able to safely resume HBOT after metronidazole was discontinued, suggesting that the combination was the causation for the development of encephalopathy. We do not believe any similar cases have been reported.

Cerebral venous thrombosis (CVT) is a rare cerebrovascular disease that affects about 5 in 1 million people each year and accounts for 0.5% of all strokes.¹ Previously it was thought to be caused most commonly by infections (eg, mastoiditis, otitis, meningitis) affecting the superior sagittal sinus and often resulting in focal neurologic deficits, seizures, coma, and death. Although local and systemic infections are still prominent risk factors in its development, CVT is now primarily recognized as a nonseptic disease with a wide spectrum of clinical presentations.

Cerebral venous thrombosis causes reduced outflow of blood and cerebrospinal fluid, which in half of affected patients leads to significant venous infarct. As opposed to arterial infarctions, CVT mainly affects children and young adults; it is an important cause of stroke in the younger population.² There is significant overlap of the many risk factors for CVT and those for venous thromboembolism (VTE): cancer, obesity, genetic thrombophilia, trauma, infection, and prior neurosurgery. However, the most common acquired risk factors for CVT are oral contraceptive use and pregnancy, which explains why CVT is 3 times more likely to occur in young and middle-aged women.³

Cerebral venous thrombosis was first recognized by a French physician in the 19th century, a time when the condition was diagnosed at autopsy, which typically showed hemorrhagic lesions at the thrombus site.⁴ For many years heparin was contraindicated in the treatment of CVT, and only within the past 25 years did advances in neuroimaging allow for earlier diagnosis and change perspectives on the management of this disease.

Cerebral venous thrombosis occurs from formation of a thrombus within the cerebral venous sinuses, leading to elevated intracranial pressure and eventually ischemia or intracranial hemorrhage. Improved imaging techniques, notably magnetic resonance imaging (MRI) and computed tomography (CT) venography, allow physicians to identify thrombus formation earlier and begin anticoagulation therapy with heparin before infarction. A meta-analysis of studies found that heparin was safer and more efficacious in treating CVT compared with placebo.⁵ Furthermore, several small randomized trials found treatment with unfractionated heparin (UFH) or low-molecularweight heparin (LMWH) was not associated with higher risk of hemorrhagic stroke in these patients.^6-8

Despite improvements in imaging modalities, in many cases diagnosis is delayed, as most patients with CVT have a wide spectrum of presentations with nonspecific symptoms, such as headache, seizure, focal sensorimotor deficits, and papilledema.⁹ Clinical presentations of CVT depend on a variety of factors, including age, time of onset, CVT location, and presence of parenchymal lesions. Isolated headache is the most common initial symptom, and in many cases is the only presenting manifestation of CVT.¹ Encephalopathy with multifocal signs, delirium, or dysfunction in executive functions most commonly occurs in elderly populations.

Cavernous sinus thrombosis most commonly produces generalized headaches, orbital pain, proptosis, and diplopia, whereas cortical vein thrombosis often produces seizures and focal sensorimotor deficits. Aphasia may be present in patients with isolated left transverse sinus thrombosis. In the presence of deep cerebral venous occlusion, patients can present in coma or with severe cognitive deficits and widespread paresis.¹⁰ Thrombosis of different veins and sinuses results in a wide spectrum of diverse clinical pictures, posing a diagnostic challenge and affecting clinical outcomes.

Given the variable and often nonspecific clinical presentations of these cases, unenhanced CT typically is the first imaging study ordered. According to the literature, noncontrast CT is not sensitive (25%-56%) in detecting CVT, and findings are normal in up to 26% of patients, rarely providing a specific diagnosis.¹¹ Furthermore, visualization on MRI can be difficult during the acute phase of CVT, as the thrombus initially appears isointense on T1-weighted images and gradually becomes hyperintense over the course of the disease process.¹² These difficulties with the usual first-choice imaging examinations often result in a delay in diagnosing CVT. However, several points on close examination of these imaging studies may help physicians establish a high index of clinical suspicion and order the appropriate follow-up studies for CVT.

The authors report the case of a patient who presented with a 1-week history of confusion, headaches, and dizziness. His nonspecific presentation along with the absence of obvious signs of CVT on imaging prolonged his diagnosis and the initiation of an appropriate treatment plan.

Case Report

A 57-year-old white air-conditioning mechanic presented to the emergency department (ED) with a 1-week history of gradual-onset confusion, severe headaches, dizziness, light-headedness, poor memory, and increased sleep. Two days earlier, he presented with similar symptoms to an outside facility, where he was admitted and underwent a workup for stroke, hemorrhage, and cardiac abnormalities—including noncontrast CT of the head. With nothing of clinical significance found, the patient was discharged and was advised to follow up on an outpatient basis.

Persisting symptoms brought the patient to the ED 1 day later, and he was admitted. He described severe, progressive, generalized headaches that were more severe when he was lying down at night and waking in the morning. He did not report that the headaches worsened with coughing or straining, and he reported no history of trauma, neck stiffness, vision change, seizures, and migraines. His medical history was significant for hypertension, dyslipidemia, and in 2011, an unprovoked deep vein thrombosis (DVT) in the right leg. He reported no history of tobacco, alcohol, or illicit drug use. He had served in the U.S. Navy, working in electronics, intelligence, data systems, and satellite communications.

On initial physical examination, the patient was afebrile and lethargic, and his blood pressure was mildly elevated (144/83 mm Hg). Cardiopulmonary examination was normal. Neurologic examination revealed no severe focal deficits, and cranial nerves II to XII were intact. Funduscopic examination was normal, with no papilledema noted. Motor strength was 5/5 bilaterally in the deltoids, biceps, triceps, radial and ulnar wrist extensors, iliopsoas, quadriceps, hamstrings, tibialis anterior and posterior, fibulares, and gastrocnemius. Pinprick sensation and light-touch sensation were decreased within the lateral bicipital region of the left upper extremity. Pinprick sensation was intact bilaterally in 1-inch increments at all other distributions along the medial and lateral aspects of the upper and lower extremities. Muscle tone and bulk were normal in all extremities. Reflexes were 2+ bilaterally in the biceps, brachioradialis, triceps, quadriceps, and Achilles. The Babinski sign was absent bilaterally, the finger-tonose and heel-to-shin tests were normal, the Romberg sign was absent, and there was no evidence of pronator drift. Laboratory test results were normal except for slightly elevated hemoglobin (17.5 g/dL) and D-dimer (588 ng/mL) levels.

Although noncontrast CT of the head initially showed no acute intracranial abnormalities, retrospective close comparison with the arterial system revealed slightly increased attenuation in the superior sagittal sinus, straight sinus, vein of Galen, and internal cerebral veins (Figures 1A and 1B) relative to the arterial carotid anterior circulation (Figures 2A and 2B).

Subsequent brain MRI without contrast showed a hyperintense T1 signal involving the superior sagittal sinus (Figures 3A and 3B), extending into the straight sinus and the vein of Galen. Magnetic resonance imaging with contrast demonstrated a prominent filling defect primarily in the superior sagittal sinus, in the right transverse sinus, and in the vein of Galen. Diffusion-weighted brain MRI sequence showed restricted diffusion localized to the right thalamic area (Figure 4) and no evidence of hemorrhage.

Treatment

International guidelines recommend using heparin to achieve rapid anticoagulation, stop the thrombotic process, and prevent extension of the thrombus.¹³ Theoretically, more rapid recanalization may have been achieved by performing endovascular thrombectomy in the present case. However, severe bleeding complications, combined with higher cost and the limited availability of clinicians experienced in treating this rare disease, convince physicians to rely on heparin as first-line treatment for CVT.¹⁴ A small randomized clinical trial found LMWH safer and more efficacious than UFH in treating CVT.¹⁵ After stabilization, oral anticoagulation therapy is used to maintain an international normalized ratio (INR) between 2.0 and 3.0 for at least 3 months.¹⁴

Given these findings, the patient was initially treated with LMWH. Eventually he was switched to oral warfarin and showed signs of clinical improvement. A hypercoagulability state workup revealed that the patient was heterozygous for the prothrombin G20210A mutation, and he was discharged and instructed to continue the oral warfarin therapy.

On follow-up, the hematology and neurology team initiated indefinite treatment with warfarin for his genetic hypercoagulability state. Monitoring of the dose of anticoagulation therapy was started to maintain INR between 2.0 and 3.0. The patient began coming to the office for INR monitoring every 2 to 3 weeks, and his most recent INR, in May 2017, was 2.66. He is taking 7.5 mg of warfarin on Wednesdays and Sundays and 5 mg on all other days and currently does not report any progressive neurologic deficits.

Discussion

The clinical findings of CVT and the hypercoagulability state workup revealed that the patient was heterozygous for the prothrombin G20210A mutation. Prothrombin is the precursor to thrombin, which is a key regulator of the clotting cascade and a promoter of coagulation. Carriers of the mutation have elevated levels of blood plasma prothrombin and have been associated with a 4 times higher risk for VTE.¹⁶

Several large studies and systematic reviews have confirmed that the prothrombin G20210A mutation is associated with higher rates of VTE, leading to an increased risk for DVT of the leg or pulmonary embolism.^17-19 More specifically, a metaanalysis of 15 case–control studies found strong associations between the mutation and CVT.²⁰ Despite this significant association, studies are inconclusive about whether heterozygosity for the mutation is associated with increased rates of recurrent CVT or other VTE in the absence of other risk factors, such as oral contraceptive use, trauma, malignancy, and infection.^21-23 Therefore, the optimal duration of anticoagulation therapy for CVT is not well established in patients with the mutation. However, the present patient was started on indefinite anticoagulation therapy because the underlying etiology of the CVT was not reversible or transient, and this CVT was his second episode of VTE, following a 2011 DVT in the right leg.

The case discussed here illustrates the clinical presentation and diagnostic complexities of CVT. Two days before coming to the ED, the patient presented to an outside facility and underwent a workup for nonspecific symptoms (eg, confusion, headaches). Due to the nonspecific presentation associated with CVT, a detailed history is imperative to distinguish symptoms suggesting increased intracranial pressure, such as headaches worse when lying down or present in the morning, with a high clinical suspicion of CVT. The ability to attain these specific details leads clinicians toward obtaining the necessary imaging studies for potential CVT patients, and may prevent delay in diagnosis and treatment. The thrombus in CVT initially consists of deoxyhemoglobin and appears on MRI as an isointense signal on T1-weighted images and a hypointense signal on T2-weighted images; over subsequent days, the thrombus changes to methemoglobin and appears as a slightly hyperintense signal on both T1- and T2-weighted images.²⁴

During this phase, there are some false negatives, as the thrombus can be mistaken for imaging artifacts, hematocrit elevations, or low flow of normal venous blood. Given the clinical findings and imaging studies, it is essential to distinguish CVT from other benign etiologies. Earlier diagnosis and initiation of anticoagulation therapy may have precluded the small amount of localized ischemic changes in this patient’s right thalamus, thus preventing the mild sensory loss in the left upper extremity. With the variable and nonspecific clinical presentations and the difficulties in identifying CVT with first-line imaging, progression of thrombus formation may lead to severe focal neurologic deficits, coma, or death.

Using CT imaging studies to compare the blood in the draining cerebral sinuses with the blood in the arterial system can help distinguish CVT from other etiologies of hyperdense abnormalities, such as increased hematocrit or decreased flow. Retrospective close examination of the present patient’s noncontrast CT images of the head and brain revealed slight hyperdensity in the cerebral sinuses compared with the arterial blood, suggesting the presence of thrombus formation in the cerebral veins. As CT is often the first study used to evaluate the nonspecific clinical presentations of these patients, identifying subtle signaldensity differences between the arterial and venous systems could guide physicians in identifying CVT earlier.

The authors reiterate the importance of meticulous imaging interpretation in light of the entire clinical picture: In these patients, it is imperative to have a high index of clinical suspicion for CVT in order to prevent more serious complications, such as ischemic or hemorrhagic stroke.

Cerebral venous thrombosis (CVT) is a rare cerebrovascular disease that affects about 5 in 1 million people each year and accounts for 0.5% of all strokes.¹ Previously it was thought to be caused most commonly by infections (eg, mastoiditis, otitis, meningitis) affecting the superior sagittal sinus and often resulting in focal neurologic deficits, seizures, coma, and death. Although local and systemic infections are still prominent risk factors in its development, CVT is now primarily recognized as a nonseptic disease with a wide spectrum of clinical presentations.

Cerebral venous thrombosis causes reduced outflow of blood and cerebrospinal fluid, which in half of affected patients leads to significant venous infarct. As opposed to arterial infarctions, CVT mainly affects children and young adults; it is an important cause of stroke in the younger population.² There is significant overlap of the many risk factors for CVT and those for venous thromboembolism (VTE): cancer, obesity, genetic thrombophilia, trauma, infection, and prior neurosurgery. However, the most common acquired risk factors for CVT are oral contraceptive use and pregnancy, which explains why CVT is 3 times more likely to occur in young and middle-aged women.³

Cerebral venous thrombosis was first recognized by a French physician in the 19th century, a time when the condition was diagnosed at autopsy, which typically showed hemorrhagic lesions at the thrombus site.⁴ For many years heparin was contraindicated in the treatment of CVT, and only within the past 25 years did advances in neuroimaging allow for earlier diagnosis and change perspectives on the management of this disease.

Cerebral venous thrombosis occurs from formation of a thrombus within the cerebral venous sinuses, leading to elevated intracranial pressure and eventually ischemia or intracranial hemorrhage. Improved imaging techniques, notably magnetic resonance imaging (MRI) and computed tomography (CT) venography, allow physicians to identify thrombus formation earlier and begin anticoagulation therapy with heparin before infarction. A meta-analysis of studies found that heparin was safer and more efficacious in treating CVT compared with placebo.⁵ Furthermore, several small randomized trials found treatment with unfractionated heparin (UFH) or low-molecularweight heparin (LMWH) was not associated with higher risk of hemorrhagic stroke in these patients.^6-8

Despite improvements in imaging modalities, in many cases diagnosis is delayed, as most patients with CVT have a wide spectrum of presentations with nonspecific symptoms, such as headache, seizure, focal sensorimotor deficits, and papilledema.⁹ Clinical presentations of CVT depend on a variety of factors, including age, time of onset, CVT location, and presence of parenchymal lesions. Isolated headache is the most common initial symptom, and in many cases is the only presenting manifestation of CVT.¹ Encephalopathy with multifocal signs, delirium, or dysfunction in executive functions most commonly occurs in elderly populations.

Cavernous sinus thrombosis most commonly produces generalized headaches, orbital pain, proptosis, and diplopia, whereas cortical vein thrombosis often produces seizures and focal sensorimotor deficits. Aphasia may be present in patients with isolated left transverse sinus thrombosis. In the presence of deep cerebral venous occlusion, patients can present in coma or with severe cognitive deficits and widespread paresis.¹⁰ Thrombosis of different veins and sinuses results in a wide spectrum of diverse clinical pictures, posing a diagnostic challenge and affecting clinical outcomes.

Given the variable and often nonspecific clinical presentations of these cases, unenhanced CT typically is the first imaging study ordered. According to the literature, noncontrast CT is not sensitive (25%-56%) in detecting CVT, and findings are normal in up to 26% of patients, rarely providing a specific diagnosis.¹¹ Furthermore, visualization on MRI can be difficult during the acute phase of CVT, as the thrombus initially appears isointense on T1-weighted images and gradually becomes hyperintense over the course of the disease process.¹² These difficulties with the usual first-choice imaging examinations often result in a delay in diagnosing CVT. However, several points on close examination of these imaging studies may help physicians establish a high index of clinical suspicion and order the appropriate follow-up studies for CVT.

The authors report the case of a patient who presented with a 1-week history of confusion, headaches, and dizziness. His nonspecific presentation along with the absence of obvious signs of CVT on imaging prolonged his diagnosis and the initiation of an appropriate treatment plan.

Case Report

A 57-year-old white air-conditioning mechanic presented to the emergency department (ED) with a 1-week history of gradual-onset confusion, severe headaches, dizziness, light-headedness, poor memory, and increased sleep. Two days earlier, he presented with similar symptoms to an outside facility, where he was admitted and underwent a workup for stroke, hemorrhage, and cardiac abnormalities—including noncontrast CT of the head. With nothing of clinical significance found, the patient was discharged and was advised to follow up on an outpatient basis.

Persisting symptoms brought the patient to the ED 1 day later, and he was admitted. He described severe, progressive, generalized headaches that were more severe when he was lying down at night and waking in the morning. He did not report that the headaches worsened with coughing or straining, and he reported no history of trauma, neck stiffness, vision change, seizures, and migraines. His medical history was significant for hypertension, dyslipidemia, and in 2011, an unprovoked deep vein thrombosis (DVT) in the right leg. He reported no history of tobacco, alcohol, or illicit drug use. He had served in the U.S. Navy, working in electronics, intelligence, data systems, and satellite communications.

On initial physical examination, the patient was afebrile and lethargic, and his blood pressure was mildly elevated (144/83 mm Hg). Cardiopulmonary examination was normal. Neurologic examination revealed no severe focal deficits, and cranial nerves II to XII were intact. Funduscopic examination was normal, with no papilledema noted. Motor strength was 5/5 bilaterally in the deltoids, biceps, triceps, radial and ulnar wrist extensors, iliopsoas, quadriceps, hamstrings, tibialis anterior and posterior, fibulares, and gastrocnemius. Pinprick sensation and light-touch sensation were decreased within the lateral bicipital region of the left upper extremity. Pinprick sensation was intact bilaterally in 1-inch increments at all other distributions along the medial and lateral aspects of the upper and lower extremities. Muscle tone and bulk were normal in all extremities. Reflexes were 2+ bilaterally in the biceps, brachioradialis, triceps, quadriceps, and Achilles. The Babinski sign was absent bilaterally, the finger-tonose and heel-to-shin tests were normal, the Romberg sign was absent, and there was no evidence of pronator drift. Laboratory test results were normal except for slightly elevated hemoglobin (17.5 g/dL) and D-dimer (588 ng/mL) levels.

Although noncontrast CT of the head initially showed no acute intracranial abnormalities, retrospective close comparison with the arterial system revealed slightly increased attenuation in the superior sagittal sinus, straight sinus, vein of Galen, and internal cerebral veins (Figures 1A and 1B) relative to the arterial carotid anterior circulation (Figures 2A and 2B).

Subsequent brain MRI without contrast showed a hyperintense T1 signal involving the superior sagittal sinus (Figures 3A and 3B), extending into the straight sinus and the vein of Galen. Magnetic resonance imaging with contrast demonstrated a prominent filling defect primarily in the superior sagittal sinus, in the right transverse sinus, and in the vein of Galen. Diffusion-weighted brain MRI sequence showed restricted diffusion localized to the right thalamic area (Figure 4) and no evidence of hemorrhage.

Treatment

International guidelines recommend using heparin to achieve rapid anticoagulation, stop the thrombotic process, and prevent extension of the thrombus.¹³ Theoretically, more rapid recanalization may have been achieved by performing endovascular thrombectomy in the present case. However, severe bleeding complications, combined with higher cost and the limited availability of clinicians experienced in treating this rare disease, convince physicians to rely on heparin as first-line treatment for CVT.¹⁴ A small randomized clinical trial found LMWH safer and more efficacious than UFH in treating CVT.¹⁵ After stabilization, oral anticoagulation therapy is used to maintain an international normalized ratio (INR) between 2.0 and 3.0 for at least 3 months.¹⁴

Given these findings, the patient was initially treated with LMWH. Eventually he was switched to oral warfarin and showed signs of clinical improvement. A hypercoagulability state workup revealed that the patient was heterozygous for the prothrombin G20210A mutation, and he was discharged and instructed to continue the oral warfarin therapy.

On follow-up, the hematology and neurology team initiated indefinite treatment with warfarin for his genetic hypercoagulability state. Monitoring of the dose of anticoagulation therapy was started to maintain INR between 2.0 and 3.0. The patient began coming to the office for INR monitoring every 2 to 3 weeks, and his most recent INR, in May 2017, was 2.66. He is taking 7.5 mg of warfarin on Wednesdays and Sundays and 5 mg on all other days and currently does not report any progressive neurologic deficits.

Discussion

The clinical findings of CVT and the hypercoagulability state workup revealed that the patient was heterozygous for the prothrombin G20210A mutation. Prothrombin is the precursor to thrombin, which is a key regulator of the clotting cascade and a promoter of coagulation. Carriers of the mutation have elevated levels of blood plasma prothrombin and have been associated with a 4 times higher risk for VTE.¹⁶

Several large studies and systematic reviews have confirmed that the prothrombin G20210A mutation is associated with higher rates of VTE, leading to an increased risk for DVT of the leg or pulmonary embolism.^17-19 More specifically, a metaanalysis of 15 case–control studies found strong associations between the mutation and CVT.²⁰ Despite this significant association, studies are inconclusive about whether heterozygosity for the mutation is associated with increased rates of recurrent CVT or other VTE in the absence of other risk factors, such as oral contraceptive use, trauma, malignancy, and infection.^21-23 Therefore, the optimal duration of anticoagulation therapy for CVT is not well established in patients with the mutation. However, the present patient was started on indefinite anticoagulation therapy because the underlying etiology of the CVT was not reversible or transient, and this CVT was his second episode of VTE, following a 2011 DVT in the right leg.

The case discussed here illustrates the clinical presentation and diagnostic complexities of CVT. Two days before coming to the ED, the patient presented to an outside facility and underwent a workup for nonspecific symptoms (eg, confusion, headaches). Due to the nonspecific presentation associated with CVT, a detailed history is imperative to distinguish symptoms suggesting increased intracranial pressure, such as headaches worse when lying down or present in the morning, with a high clinical suspicion of CVT. The ability to attain these specific details leads clinicians toward obtaining the necessary imaging studies for potential CVT patients, and may prevent delay in diagnosis and treatment. The thrombus in CVT initially consists of deoxyhemoglobin and appears on MRI as an isointense signal on T1-weighted images and a hypointense signal on T2-weighted images; over subsequent days, the thrombus changes to methemoglobin and appears as a slightly hyperintense signal on both T1- and T2-weighted images.²⁴

During this phase, there are some false negatives, as the thrombus can be mistaken for imaging artifacts, hematocrit elevations, or low flow of normal venous blood. Given the clinical findings and imaging studies, it is essential to distinguish CVT from other benign etiologies. Earlier diagnosis and initiation of anticoagulation therapy may have precluded the small amount of localized ischemic changes in this patient’s right thalamus, thus preventing the mild sensory loss in the left upper extremity. With the variable and nonspecific clinical presentations and the difficulties in identifying CVT with first-line imaging, progression of thrombus formation may lead to severe focal neurologic deficits, coma, or death.

Using CT imaging studies to compare the blood in the draining cerebral sinuses with the blood in the arterial system can help distinguish CVT from other etiologies of hyperdense abnormalities, such as increased hematocrit or decreased flow. Retrospective close examination of the present patient’s noncontrast CT images of the head and brain revealed slight hyperdensity in the cerebral sinuses compared with the arterial blood, suggesting the presence of thrombus formation in the cerebral veins. As CT is often the first study used to evaluate the nonspecific clinical presentations of these patients, identifying subtle signaldensity differences between the arterial and venous systems could guide physicians in identifying CVT earlier.

The authors reiterate the importance of meticulous imaging interpretation in light of the entire clinical picture: In these patients, it is imperative to have a high index of clinical suspicion for CVT in order to prevent more serious complications, such as ischemic or hemorrhagic stroke.

Cerebral venous thrombosis (CVT) is a rare cerebrovascular disease that affects about 5 in 1 million people each year and accounts for 0.5% of all strokes.¹ Previously it was thought to be caused most commonly by infections (eg, mastoiditis, otitis, meningitis) affecting the superior sagittal sinus and often resulting in focal neurologic deficits, seizures, coma, and death. Although local and systemic infections are still prominent risk factors in its development, CVT is now primarily recognized as a nonseptic disease with a wide spectrum of clinical presentations.

Cerebral venous thrombosis causes reduced outflow of blood and cerebrospinal fluid, which in half of affected patients leads to significant venous infarct. As opposed to arterial infarctions, CVT mainly affects children and young adults; it is an important cause of stroke in the younger population.² There is significant overlap of the many risk factors for CVT and those for venous thromboembolism (VTE): cancer, obesity, genetic thrombophilia, trauma, infection, and prior neurosurgery. However, the most common acquired risk factors for CVT are oral contraceptive use and pregnancy, which explains why CVT is 3 times more likely to occur in young and middle-aged women.³

Cerebral venous thrombosis was first recognized by a French physician in the 19th century, a time when the condition was diagnosed at autopsy, which typically showed hemorrhagic lesions at the thrombus site.⁴ For many years heparin was contraindicated in the treatment of CVT, and only within the past 25 years did advances in neuroimaging allow for earlier diagnosis and change perspectives on the management of this disease.

Cerebral venous thrombosis occurs from formation of a thrombus within the cerebral venous sinuses, leading to elevated intracranial pressure and eventually ischemia or intracranial hemorrhage. Improved imaging techniques, notably magnetic resonance imaging (MRI) and computed tomography (CT) venography, allow physicians to identify thrombus formation earlier and begin anticoagulation therapy with heparin before infarction. A meta-analysis of studies found that heparin was safer and more efficacious in treating CVT compared with placebo.⁵ Furthermore, several small randomized trials found treatment with unfractionated heparin (UFH) or low-molecularweight heparin (LMWH) was not associated with higher risk of hemorrhagic stroke in these patients.^6-8

Despite improvements in imaging modalities, in many cases diagnosis is delayed, as most patients with CVT have a wide spectrum of presentations with nonspecific symptoms, such as headache, seizure, focal sensorimotor deficits, and papilledema.⁹ Clinical presentations of CVT depend on a variety of factors, including age, time of onset, CVT location, and presence of parenchymal lesions. Isolated headache is the most common initial symptom, and in many cases is the only presenting manifestation of CVT.¹ Encephalopathy with multifocal signs, delirium, or dysfunction in executive functions most commonly occurs in elderly populations.

Cavernous sinus thrombosis most commonly produces generalized headaches, orbital pain, proptosis, and diplopia, whereas cortical vein thrombosis often produces seizures and focal sensorimotor deficits. Aphasia may be present in patients with isolated left transverse sinus thrombosis. In the presence of deep cerebral venous occlusion, patients can present in coma or with severe cognitive deficits and widespread paresis.¹⁰ Thrombosis of different veins and sinuses results in a wide spectrum of diverse clinical pictures, posing a diagnostic challenge and affecting clinical outcomes.

Given the variable and often nonspecific clinical presentations of these cases, unenhanced CT typically is the first imaging study ordered. According to the literature, noncontrast CT is not sensitive (25%-56%) in detecting CVT, and findings are normal in up to 26% of patients, rarely providing a specific diagnosis.¹¹ Furthermore, visualization on MRI can be difficult during the acute phase of CVT, as the thrombus initially appears isointense on T1-weighted images and gradually becomes hyperintense over the course of the disease process.¹² These difficulties with the usual first-choice imaging examinations often result in a delay in diagnosing CVT. However, several points on close examination of these imaging studies may help physicians establish a high index of clinical suspicion and order the appropriate follow-up studies for CVT.

The authors report the case of a patient who presented with a 1-week history of confusion, headaches, and dizziness. His nonspecific presentation along with the absence of obvious signs of CVT on imaging prolonged his diagnosis and the initiation of an appropriate treatment plan.

Case Report

A 57-year-old white air-conditioning mechanic presented to the emergency department (ED) with a 1-week history of gradual-onset confusion, severe headaches, dizziness, light-headedness, poor memory, and increased sleep. Two days earlier, he presented with similar symptoms to an outside facility, where he was admitted and underwent a workup for stroke, hemorrhage, and cardiac abnormalities—including noncontrast CT of the head. With nothing of clinical significance found, the patient was discharged and was advised to follow up on an outpatient basis.

Persisting symptoms brought the patient to the ED 1 day later, and he was admitted. He described severe, progressive, generalized headaches that were more severe when he was lying down at night and waking in the morning. He did not report that the headaches worsened with coughing or straining, and he reported no history of trauma, neck stiffness, vision change, seizures, and migraines. His medical history was significant for hypertension, dyslipidemia, and in 2011, an unprovoked deep vein thrombosis (DVT) in the right leg. He reported no history of tobacco, alcohol, or illicit drug use. He had served in the U.S. Navy, working in electronics, intelligence, data systems, and satellite communications.

On initial physical examination, the patient was afebrile and lethargic, and his blood pressure was mildly elevated (144/83 mm Hg). Cardiopulmonary examination was normal. Neurologic examination revealed no severe focal deficits, and cranial nerves II to XII were intact. Funduscopic examination was normal, with no papilledema noted. Motor strength was 5/5 bilaterally in the deltoids, biceps, triceps, radial and ulnar wrist extensors, iliopsoas, quadriceps, hamstrings, tibialis anterior and posterior, fibulares, and gastrocnemius. Pinprick sensation and light-touch sensation were decreased within the lateral bicipital region of the left upper extremity. Pinprick sensation was intact bilaterally in 1-inch increments at all other distributions along the medial and lateral aspects of the upper and lower extremities. Muscle tone and bulk were normal in all extremities. Reflexes were 2+ bilaterally in the biceps, brachioradialis, triceps, quadriceps, and Achilles. The Babinski sign was absent bilaterally, the finger-tonose and heel-to-shin tests were normal, the Romberg sign was absent, and there was no evidence of pronator drift. Laboratory test results were normal except for slightly elevated hemoglobin (17.5 g/dL) and D-dimer (588 ng/mL) levels.

Although noncontrast CT of the head initially showed no acute intracranial abnormalities, retrospective close comparison with the arterial system revealed slightly increased attenuation in the superior sagittal sinus, straight sinus, vein of Galen, and internal cerebral veins (Figures 1A and 1B) relative to the arterial carotid anterior circulation (Figures 2A and 2B).

Subsequent brain MRI without contrast showed a hyperintense T1 signal involving the superior sagittal sinus (Figures 3A and 3B), extending into the straight sinus and the vein of Galen. Magnetic resonance imaging with contrast demonstrated a prominent filling defect primarily in the superior sagittal sinus, in the right transverse sinus, and in the vein of Galen. Diffusion-weighted brain MRI sequence showed restricted diffusion localized to the right thalamic area (Figure 4) and no evidence of hemorrhage.

Treatment

International guidelines recommend using heparin to achieve rapid anticoagulation, stop the thrombotic process, and prevent extension of the thrombus.¹³ Theoretically, more rapid recanalization may have been achieved by performing endovascular thrombectomy in the present case. However, severe bleeding complications, combined with higher cost and the limited availability of clinicians experienced in treating this rare disease, convince physicians to rely on heparin as first-line treatment for CVT.¹⁴ A small randomized clinical trial found LMWH safer and more efficacious than UFH in treating CVT.¹⁵ After stabilization, oral anticoagulation therapy is used to maintain an international normalized ratio (INR) between 2.0 and 3.0 for at least 3 months.¹⁴

Given these findings, the patient was initially treated with LMWH. Eventually he was switched to oral warfarin and showed signs of clinical improvement. A hypercoagulability state workup revealed that the patient was heterozygous for the prothrombin G20210A mutation, and he was discharged and instructed to continue the oral warfarin therapy.

On follow-up, the hematology and neurology team initiated indefinite treatment with warfarin for his genetic hypercoagulability state. Monitoring of the dose of anticoagulation therapy was started to maintain INR between 2.0 and 3.0. The patient began coming to the office for INR monitoring every 2 to 3 weeks, and his most recent INR, in May 2017, was 2.66. He is taking 7.5 mg of warfarin on Wednesdays and Sundays and 5 mg on all other days and currently does not report any progressive neurologic deficits.

Discussion

The clinical findings of CVT and the hypercoagulability state workup revealed that the patient was heterozygous for the prothrombin G20210A mutation. Prothrombin is the precursor to thrombin, which is a key regulator of the clotting cascade and a promoter of coagulation. Carriers of the mutation have elevated levels of blood plasma prothrombin and have been associated with a 4 times higher risk for VTE.¹⁶

Several large studies and systematic reviews have confirmed that the prothrombin G20210A mutation is associated with higher rates of VTE, leading to an increased risk for DVT of the leg or pulmonary embolism.^17-19 More specifically, a metaanalysis of 15 case–control studies found strong associations between the mutation and CVT.²⁰ Despite this significant association, studies are inconclusive about whether heterozygosity for the mutation is associated with increased rates of recurrent CVT or other VTE in the absence of other risk factors, such as oral contraceptive use, trauma, malignancy, and infection.^21-23 Therefore, the optimal duration of anticoagulation therapy for CVT is not well established in patients with the mutation. However, the present patient was started on indefinite anticoagulation therapy because the underlying etiology of the CVT was not reversible or transient, and this CVT was his second episode of VTE, following a 2011 DVT in the right leg.

The case discussed here illustrates the clinical presentation and diagnostic complexities of CVT. Two days before coming to the ED, the patient presented to an outside facility and underwent a workup for nonspecific symptoms (eg, confusion, headaches). Due to the nonspecific presentation associated with CVT, a detailed history is imperative to distinguish symptoms suggesting increased intracranial pressure, such as headaches worse when lying down or present in the morning, with a high clinical suspicion of CVT. The ability to attain these specific details leads clinicians toward obtaining the necessary imaging studies for potential CVT patients, and may prevent delay in diagnosis and treatment. The thrombus in CVT initially consists of deoxyhemoglobin and appears on MRI as an isointense signal on T1-weighted images and a hypointense signal on T2-weighted images; over subsequent days, the thrombus changes to methemoglobin and appears as a slightly hyperintense signal on both T1- and T2-weighted images.²⁴

During this phase, there are some false negatives, as the thrombus can be mistaken for imaging artifacts, hematocrit elevations, or low flow of normal venous blood. Given the clinical findings and imaging studies, it is essential to distinguish CVT from other benign etiologies. Earlier diagnosis and initiation of anticoagulation therapy may have precluded the small amount of localized ischemic changes in this patient’s right thalamus, thus preventing the mild sensory loss in the left upper extremity. With the variable and nonspecific clinical presentations and the difficulties in identifying CVT with first-line imaging, progression of thrombus formation may lead to severe focal neurologic deficits, coma, or death.

Using CT imaging studies to compare the blood in the draining cerebral sinuses with the blood in the arterial system can help distinguish CVT from other etiologies of hyperdense abnormalities, such as increased hematocrit or decreased flow. Retrospective close examination of the present patient’s noncontrast CT images of the head and brain revealed slight hyperdensity in the cerebral sinuses compared with the arterial blood, suggesting the presence of thrombus formation in the cerebral veins. As CT is often the first study used to evaluate the nonspecific clinical presentations of these patients, identifying subtle signaldensity differences between the arterial and venous systems could guide physicians in identifying CVT earlier.

The authors reiterate the importance of meticulous imaging interpretation in light of the entire clinical picture: In these patients, it is imperative to have a high index of clinical suspicion for CVT in order to prevent more serious complications, such as ischemic or hemorrhagic stroke.