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When, in 2022, singer and international celebrity Celine Dion announced what she called her “one-in-a-million diagnosis” of stiff person syndrome, clinicians and medical scientists who specialize in the disorder took a deep breath. Scott D. Newsome, DO, professor of neurology and director of the Johns Hopkins Stiff Person Syndrome Center, Baltimore – a glass-half-full kind of person – saw in Ms. Dion’s worrying announcement a huge opportunity nonetheless: To raise awareness about the rare cluster of disorders known collectively as stiff person spectrum disorders (SPSD).
“Even at the clinician level, if you don’t know the hallmark signs and symptoms, you could possibly misdiagnose it,” Dr. Newsome said in an interview.
But misdiagnosis can go either way; increased awareness of SPSD can have a downside. Thirty years ago, when Marinos C. Dalakas, MD, first began studying SPSD, the diagnosis was frequently missed – “because people were not aware of it,” he said. But now, Dr. Dalakas, professor of neurology and director of the division of neuromuscular diseases in the department of neurology at Thomas Jefferson University and the Jefferson Hospital for Neuroscience, both in Philadelphia, said overdiagnosis is also a concern, particularly with increased public awareness.
“Just this last month I saw two patients who told me: ‘I read about it, and I believe I have symptoms of stiff person,’ ” he said.
These days, most patients in whom SPSD is suspected end up with an alternate diagnosis. In a recent retrospective study that Dr. Dalakas coauthored, of 173 patients who had been referred to the Mayo Clinic in Rochester, Minn., with suspected SPSD,1 Dr. Dalakas and colleagues determined that only 48 (27.7%) actually had the disorder – meaning that the rest might have been unnecessarily exposed to immunosuppressive SPSD therapies and that treatment for their actual disorder (most often, a functional neurologic disorder or nonneurologic condition) was delayed.
At the root of both underdiagnosis and overdiagnosis of SPSD is the heterogeneity of the condition and a lack of definitive diagnostic markers.
SPSD has been considered an autoimmune disorder for a long time, and observations by Dr. Dalakas and others have shown that as many as 35% of cases co-occur with another autoimmune disease, such as vitiligo, celiac disease, rheumatologic disease, type 1 diabetes mellitus, and thyroid disease (Grave’s disease and Hashimoto’s thyroiditis).2 A more recent study by his group observed an even higher rate (42%) of comorbid autoimmunity, with autoimmune thyroid disease being most common. However, although most cases of SPDS are characterized by an elevated level of glutamic acid decarboxylase (GAD)65-IgG, these autoantibodies are not specific to SPSD (low levels are also seen in diabetes, thyroid disease, healthy controls, etc.). Some SPSD patients have less common autoantibodies and a minority has no autoantibodies. Dr. Newsome said seronegative cases and the antibody presence and titers not being associated with disease severity or treatment response are clues that “SPSD does not appear to be a primary antibody-mediated condition and that there must be other immune factors at play.”
Autoimmune process drives SPSD
Autoimmunity, even if not detected by serologic studies, is believed to inhibit expression of gamma aminobutyric acid (GABA) receptors, which, in turn, results in stiffness and spasms. Although what are known as “Dalakas criteria,” proposed in 2009,2 describe the “classic” SPSD phenotype, encompassing roughly three-quarters of SPSD patients, there have now been other phenotypes proposed under SPSD, including isolated forms (stiff limb or trunk syndrome) and “nonclassic” phenotypes like SPS-plus (classic features plus brain stem and/or cerebellar involvement),3 overlap syndromes (for example, classic features with refractory epilepsy/limbic encephalitis), and probably the most severe phenotype, progressive encephalomyelitis with rigidity and myoclonus.
Early and aggressive therapy with benzodiazepines and other GABA-ergic agonists, as well as immune-based treatments, is considered critical to slowing progression of SPSD. However, the insidious onset of what is often a cluster of vague, nonspecific symptoms is a challenge for clinicians to recognize.
“When a patient comes in with muscular spasms, with stiffness in the back, in the legs, and it’s unexplained and it’s not due to spinal cord disease, or multiple sclerosis ... think SPSD,” said Dr. Dalakas. “Check antibodies – that’s the first thing to do.”
Antibody positivity is most helpful at high levels, he added; low titers can be present in autoimmune diabetes and other conditions, as previously mentioned. The real challenge? When a patient is seronegative.
Embarking on a diagnostic odyssey
Patients “bounce from one clinician to the next looking for answers,” said Dr. Newsome. “Patients will often start with their general practitioner and be referred to physical therapy, rheumatology, or orthopedics, and other specialists, which could include neurology and/or psychiatry, among others. SPSD is often not considered as a possible diagnosis until the patient develops more concrete symptoms and/or objective signs on exam. Of course, considering this diagnosis starts at knowing that it exists.”
Task-specific phobias and exaggerated acoustic startle or sensory reflex are specific symptoms that can red-flag some SPSD patients, said Dr. Dalakas. “Impaired GABA is also important for fears and anxiety. So, when you have a reduction of GABA you have more phobic neuroses – fear of crossing the street, fear of speaking in public, and they get very tense and they cannot perform.
“If the GABA-ergic pathways are dysfunctional, then there’s a relative hyper-excitability within the nervous system,” said Dr. Newsome. “This can be evaluated with electromyography. “The muscles are unhinged and going crazy: Agonists and antagonists are contracting together, which is abnormal. We will also assess for continuous motor unit potential activity within individual muscles – angry muscles just continuously firing. In our experience, this finding appears to be a pretty specific sign of SPS, especially in the torso.” Importantly, the sudden contraction of muscles along with stiffness can lead to traumatic falls, causing major orthopedic and brain injury.
In early stages of SPSD, a careful history and clinical exam is critical to try to shorten what Dr. Newsome calls the patient’s “diagnostic odyssey.”
“It behooves the clinician to put their hands on the patient. Check their back, their abdomen – try to feel for rigidity, paraspinal muscle spasms, and tightness. These regions of the body often have a ropey feel to them, which is due to chronic muscle spasms and tightness. Most [SPSD] patients will have this present in the thoracolumbar area,” he explained. “Check for hyperlordosis, as this is a hallmark sign on exam in SPSD. Additionally, patients can have rigidity and spasticity in their legs or arms. Also, patients with nonclassical phenotypes can present with a variety of other symptoms and findings on exam, including ataxia, nystagmus, ophthalmoparesis, and dysarthria.”
Lumbar puncture can sometimes reveal signs of inflammation, such as an elevated white blood cell count and oligoclonal bands in spinal fluid.
“The classic teaching was that you can only see such findings in conditions like multiple sclerosis, but that’s not the case,” said Dr. Newsome. “You can see these findings in other autoimmune conditions, including SPSD. Hence, as part of the workup, we will have patients undergo lumbar punctures to assess for these markers of autoimmunity.”
Other mimics of SPSD, including multiple sclerosis, tumors, and spinal stenosis, should be ruled out with MRI of the brain and spine.
Treatment options
Because of wide variability in signs and symptoms of the disorder, treatment of SPSD is a highly individualized cocktail of interventions, which might include immunotherapy and GABA-ergic agonists, as well as nonmedication treatments. The response to these agents can be difficult to quantify.
Benzodiazepines (diazepam, clonazepam, baclofen) along with other oral symptomatic treatments are often recommended as first-line therapy because of their ability to enhance GABA.4
First-line immunotherapy is usually intravenous immunoglobulin, steroids, or plasmapheresis. Second- and third-line agents include rituximab, mycophenolate mofetil, azathioprine, cyclophosphamide, and combination immune treatments.
Dr. Newsome and Dr. Dalakas have independently published a step-by-step therapeutic approach to SPSD.3,5 But in patients with paraneoplastic stiff person syndrome, eradication of their cancer is critical, although, per Dr. Newsome, “this does not always cure SPS and most of these patients still have residual disability.”
But immune-based therapies are only part of what should be a multipronged treatment approach, said Dr. Newsome. He also strongly advocates for non-pharmacological interventions, such as selective physical therapy (stretching, ultrasound, and gait and balance training), heat therapy, aquatherapy, deep-tissue massage or myofascial techniques, osteopathic or chiropractic manipulation, acupuncture, and acupressure.3
Because SPSD is considered a progressive disorder for some, a reasonable goal of treatment is to prevent worsening, said Dr. Newsome. This can take time: “We don’t expect the treatments to work overnight. It involves consecutive months and, sometimes, a couple of years of immune treatment before you start to see it impact the person’s life favorably.”
Patients who are not well informed about the long-term goal of treatments might be tempted to abandon the treatments prematurely because they don’t see immediate results, Dr. Newsome added. Encouraging realistic expectations is also important, without dashing hopes.
“I have patients who were marathon runners, and they want to get back to doing marathons. I would love nothing more than for people to get back to their pre-SPSD levels of function. But this may not be a realistic goal. However, this does not mean that quality of life can’t be helped.”
Nevertheless, Dr. Newsome encourages clinicians to reassess regularly, especially because lack of disease biomarkers makes it hard to objectively monitor the impact of therapy.
“It’s always a good rule of thumb, especially in the rare disease space, to step back and ask: ‘Are we on the right treatment path or not?’ If we’re not, then it is important to make sure you have the correct diagnosis. Even when you have a patient who fits the textbook and you, yourself, diagnosed them, it is important to continue to re-evaluate the diagnosis over time, especially if there is consideration of changing treatments. It is also important to make sure there is not something else on top of the stiff person syndrome that is working in parallel to worsen their condition.”
Be alert for comorbidity
Undiagnosed comorbid conditions that can complicate SPSD include Parkinson’s disease or myasthenia gravis, to name a couple, which Dr. Newsome has seen more than once. “We’ve seen a few people over the years who have both SPSD and another autoimmune or degenerative neurological condition.”
Diabetes also co-occurs in approximately 30% of people with SPSD, said Dr. Dalakas. “Endocrinologists should also be aware of this connection.”
Paraneoplastic stiff person syndrome is thought to be triggered by cancer, which might not have been diagnosed, making it important to work up patients for malignancy – particularly breast cancer, small cell lung cancer, lymphoma, and thymoma, Dr. Newsome advised.
Although most cases of SPSD are diagnosed in mid-life, the disorder can occur in teenagers and the elderly.
“It’s not the first thing you think of when a 70-year-old patient comes with neck pain, so it’s missed more often, and the prognosis is worse,” Dr. Dalakas warned.
What does the future hold?
Like Dr. Newsome, Dr. Dalakas is encouraged when SPSD hits the headlines because, generally, awareness facilitates diagnosis and research. (Both clinicians serve on the medical advisory board of The Stiff Person Syndrome Research Foundation.)
“We are looking for better therapies that target immune factors,” said Dr. Dalakas. “There are several of those that are relevant, so we need to select the best immune marker that we think plays a role in the antibody production,” he said.
“There’s a lot of hope – at least I have a lot of hope for what the future holds with SPSD,” added Dr. Newsome. “More research is needed and it starts with awareness of SPSD.”
Dr. Newsome discloses that he has received consulting fees for serving on scientific advisory boards of Biogen, Genentech, Bristol Myers Squibb, EMD Serono, Jazz Pharmaceuticals, Novartis, Horizon Therapeutics, TG Therapeutics; is the study lead principal investigator for a Roche clinical trial; and has received research funding (paid directly to his employing institution) from Biogen, Roche, Lundbeck, Genentech, The Stiff Person Syndrome Research Foundation, National Multiple Sclerosis Society, U.S. Department of Defense, and Patient-Centered Outcomes Research Institute. Dr. Dalakas reports nothing relevant to disclose.
References
1. Chia NH et al. Ann Clin Transl Neurol. 2023;10(7):1083-94. doi: 10.1002/acn3.51791.
2. Dalakas MC.. Curr Treat Options Neurol. 2009;11(2):102-10. doi: 10.1007/s11940-009-0013-9.
3. Newsome SD and Johnson T. J Neuroimmunol. 2022;369:577915. doi: 10.1016/j.jneuroim.2022.577915.
4. Ortiz JF et al. Cureus. 2020;12(12):e11995. doi: 10.7759/cureus.11995.
5. Dalakas CD. Neurol Neuroimmunol Neuroinflamm. 2023;10(3):e200109. doi: 10.1212/NXI.0000000000200109.
When, in 2022, singer and international celebrity Celine Dion announced what she called her “one-in-a-million diagnosis” of stiff person syndrome, clinicians and medical scientists who specialize in the disorder took a deep breath. Scott D. Newsome, DO, professor of neurology and director of the Johns Hopkins Stiff Person Syndrome Center, Baltimore – a glass-half-full kind of person – saw in Ms. Dion’s worrying announcement a huge opportunity nonetheless: To raise awareness about the rare cluster of disorders known collectively as stiff person spectrum disorders (SPSD).
“Even at the clinician level, if you don’t know the hallmark signs and symptoms, you could possibly misdiagnose it,” Dr. Newsome said in an interview.
But misdiagnosis can go either way; increased awareness of SPSD can have a downside. Thirty years ago, when Marinos C. Dalakas, MD, first began studying SPSD, the diagnosis was frequently missed – “because people were not aware of it,” he said. But now, Dr. Dalakas, professor of neurology and director of the division of neuromuscular diseases in the department of neurology at Thomas Jefferson University and the Jefferson Hospital for Neuroscience, both in Philadelphia, said overdiagnosis is also a concern, particularly with increased public awareness.
“Just this last month I saw two patients who told me: ‘I read about it, and I believe I have symptoms of stiff person,’ ” he said.
These days, most patients in whom SPSD is suspected end up with an alternate diagnosis. In a recent retrospective study that Dr. Dalakas coauthored, of 173 patients who had been referred to the Mayo Clinic in Rochester, Minn., with suspected SPSD,1 Dr. Dalakas and colleagues determined that only 48 (27.7%) actually had the disorder – meaning that the rest might have been unnecessarily exposed to immunosuppressive SPSD therapies and that treatment for their actual disorder (most often, a functional neurologic disorder or nonneurologic condition) was delayed.
At the root of both underdiagnosis and overdiagnosis of SPSD is the heterogeneity of the condition and a lack of definitive diagnostic markers.
SPSD has been considered an autoimmune disorder for a long time, and observations by Dr. Dalakas and others have shown that as many as 35% of cases co-occur with another autoimmune disease, such as vitiligo, celiac disease, rheumatologic disease, type 1 diabetes mellitus, and thyroid disease (Grave’s disease and Hashimoto’s thyroiditis).2 A more recent study by his group observed an even higher rate (42%) of comorbid autoimmunity, with autoimmune thyroid disease being most common. However, although most cases of SPDS are characterized by an elevated level of glutamic acid decarboxylase (GAD)65-IgG, these autoantibodies are not specific to SPSD (low levels are also seen in diabetes, thyroid disease, healthy controls, etc.). Some SPSD patients have less common autoantibodies and a minority has no autoantibodies. Dr. Newsome said seronegative cases and the antibody presence and titers not being associated with disease severity or treatment response are clues that “SPSD does not appear to be a primary antibody-mediated condition and that there must be other immune factors at play.”
Autoimmune process drives SPSD
Autoimmunity, even if not detected by serologic studies, is believed to inhibit expression of gamma aminobutyric acid (GABA) receptors, which, in turn, results in stiffness and spasms. Although what are known as “Dalakas criteria,” proposed in 2009,2 describe the “classic” SPSD phenotype, encompassing roughly three-quarters of SPSD patients, there have now been other phenotypes proposed under SPSD, including isolated forms (stiff limb or trunk syndrome) and “nonclassic” phenotypes like SPS-plus (classic features plus brain stem and/or cerebellar involvement),3 overlap syndromes (for example, classic features with refractory epilepsy/limbic encephalitis), and probably the most severe phenotype, progressive encephalomyelitis with rigidity and myoclonus.
Early and aggressive therapy with benzodiazepines and other GABA-ergic agonists, as well as immune-based treatments, is considered critical to slowing progression of SPSD. However, the insidious onset of what is often a cluster of vague, nonspecific symptoms is a challenge for clinicians to recognize.
“When a patient comes in with muscular spasms, with stiffness in the back, in the legs, and it’s unexplained and it’s not due to spinal cord disease, or multiple sclerosis ... think SPSD,” said Dr. Dalakas. “Check antibodies – that’s the first thing to do.”
Antibody positivity is most helpful at high levels, he added; low titers can be present in autoimmune diabetes and other conditions, as previously mentioned. The real challenge? When a patient is seronegative.
Embarking on a diagnostic odyssey
Patients “bounce from one clinician to the next looking for answers,” said Dr. Newsome. “Patients will often start with their general practitioner and be referred to physical therapy, rheumatology, or orthopedics, and other specialists, which could include neurology and/or psychiatry, among others. SPSD is often not considered as a possible diagnosis until the patient develops more concrete symptoms and/or objective signs on exam. Of course, considering this diagnosis starts at knowing that it exists.”
Task-specific phobias and exaggerated acoustic startle or sensory reflex are specific symptoms that can red-flag some SPSD patients, said Dr. Dalakas. “Impaired GABA is also important for fears and anxiety. So, when you have a reduction of GABA you have more phobic neuroses – fear of crossing the street, fear of speaking in public, and they get very tense and they cannot perform.
“If the GABA-ergic pathways are dysfunctional, then there’s a relative hyper-excitability within the nervous system,” said Dr. Newsome. “This can be evaluated with electromyography. “The muscles are unhinged and going crazy: Agonists and antagonists are contracting together, which is abnormal. We will also assess for continuous motor unit potential activity within individual muscles – angry muscles just continuously firing. In our experience, this finding appears to be a pretty specific sign of SPS, especially in the torso.” Importantly, the sudden contraction of muscles along with stiffness can lead to traumatic falls, causing major orthopedic and brain injury.
In early stages of SPSD, a careful history and clinical exam is critical to try to shorten what Dr. Newsome calls the patient’s “diagnostic odyssey.”
“It behooves the clinician to put their hands on the patient. Check their back, their abdomen – try to feel for rigidity, paraspinal muscle spasms, and tightness. These regions of the body often have a ropey feel to them, which is due to chronic muscle spasms and tightness. Most [SPSD] patients will have this present in the thoracolumbar area,” he explained. “Check for hyperlordosis, as this is a hallmark sign on exam in SPSD. Additionally, patients can have rigidity and spasticity in their legs or arms. Also, patients with nonclassical phenotypes can present with a variety of other symptoms and findings on exam, including ataxia, nystagmus, ophthalmoparesis, and dysarthria.”
Lumbar puncture can sometimes reveal signs of inflammation, such as an elevated white blood cell count and oligoclonal bands in spinal fluid.
“The classic teaching was that you can only see such findings in conditions like multiple sclerosis, but that’s not the case,” said Dr. Newsome. “You can see these findings in other autoimmune conditions, including SPSD. Hence, as part of the workup, we will have patients undergo lumbar punctures to assess for these markers of autoimmunity.”
Other mimics of SPSD, including multiple sclerosis, tumors, and spinal stenosis, should be ruled out with MRI of the brain and spine.
Treatment options
Because of wide variability in signs and symptoms of the disorder, treatment of SPSD is a highly individualized cocktail of interventions, which might include immunotherapy and GABA-ergic agonists, as well as nonmedication treatments. The response to these agents can be difficult to quantify.
Benzodiazepines (diazepam, clonazepam, baclofen) along with other oral symptomatic treatments are often recommended as first-line therapy because of their ability to enhance GABA.4
First-line immunotherapy is usually intravenous immunoglobulin, steroids, or plasmapheresis. Second- and third-line agents include rituximab, mycophenolate mofetil, azathioprine, cyclophosphamide, and combination immune treatments.
Dr. Newsome and Dr. Dalakas have independently published a step-by-step therapeutic approach to SPSD.3,5 But in patients with paraneoplastic stiff person syndrome, eradication of their cancer is critical, although, per Dr. Newsome, “this does not always cure SPS and most of these patients still have residual disability.”
But immune-based therapies are only part of what should be a multipronged treatment approach, said Dr. Newsome. He also strongly advocates for non-pharmacological interventions, such as selective physical therapy (stretching, ultrasound, and gait and balance training), heat therapy, aquatherapy, deep-tissue massage or myofascial techniques, osteopathic or chiropractic manipulation, acupuncture, and acupressure.3
Because SPSD is considered a progressive disorder for some, a reasonable goal of treatment is to prevent worsening, said Dr. Newsome. This can take time: “We don’t expect the treatments to work overnight. It involves consecutive months and, sometimes, a couple of years of immune treatment before you start to see it impact the person’s life favorably.”
Patients who are not well informed about the long-term goal of treatments might be tempted to abandon the treatments prematurely because they don’t see immediate results, Dr. Newsome added. Encouraging realistic expectations is also important, without dashing hopes.
“I have patients who were marathon runners, and they want to get back to doing marathons. I would love nothing more than for people to get back to their pre-SPSD levels of function. But this may not be a realistic goal. However, this does not mean that quality of life can’t be helped.”
Nevertheless, Dr. Newsome encourages clinicians to reassess regularly, especially because lack of disease biomarkers makes it hard to objectively monitor the impact of therapy.
“It’s always a good rule of thumb, especially in the rare disease space, to step back and ask: ‘Are we on the right treatment path or not?’ If we’re not, then it is important to make sure you have the correct diagnosis. Even when you have a patient who fits the textbook and you, yourself, diagnosed them, it is important to continue to re-evaluate the diagnosis over time, especially if there is consideration of changing treatments. It is also important to make sure there is not something else on top of the stiff person syndrome that is working in parallel to worsen their condition.”
Be alert for comorbidity
Undiagnosed comorbid conditions that can complicate SPSD include Parkinson’s disease or myasthenia gravis, to name a couple, which Dr. Newsome has seen more than once. “We’ve seen a few people over the years who have both SPSD and another autoimmune or degenerative neurological condition.”
Diabetes also co-occurs in approximately 30% of people with SPSD, said Dr. Dalakas. “Endocrinologists should also be aware of this connection.”
Paraneoplastic stiff person syndrome is thought to be triggered by cancer, which might not have been diagnosed, making it important to work up patients for malignancy – particularly breast cancer, small cell lung cancer, lymphoma, and thymoma, Dr. Newsome advised.
Although most cases of SPSD are diagnosed in mid-life, the disorder can occur in teenagers and the elderly.
“It’s not the first thing you think of when a 70-year-old patient comes with neck pain, so it’s missed more often, and the prognosis is worse,” Dr. Dalakas warned.
What does the future hold?
Like Dr. Newsome, Dr. Dalakas is encouraged when SPSD hits the headlines because, generally, awareness facilitates diagnosis and research. (Both clinicians serve on the medical advisory board of The Stiff Person Syndrome Research Foundation.)
“We are looking for better therapies that target immune factors,” said Dr. Dalakas. “There are several of those that are relevant, so we need to select the best immune marker that we think plays a role in the antibody production,” he said.
“There’s a lot of hope – at least I have a lot of hope for what the future holds with SPSD,” added Dr. Newsome. “More research is needed and it starts with awareness of SPSD.”
Dr. Newsome discloses that he has received consulting fees for serving on scientific advisory boards of Biogen, Genentech, Bristol Myers Squibb, EMD Serono, Jazz Pharmaceuticals, Novartis, Horizon Therapeutics, TG Therapeutics; is the study lead principal investigator for a Roche clinical trial; and has received research funding (paid directly to his employing institution) from Biogen, Roche, Lundbeck, Genentech, The Stiff Person Syndrome Research Foundation, National Multiple Sclerosis Society, U.S. Department of Defense, and Patient-Centered Outcomes Research Institute. Dr. Dalakas reports nothing relevant to disclose.
References
1. Chia NH et al. Ann Clin Transl Neurol. 2023;10(7):1083-94. doi: 10.1002/acn3.51791.
2. Dalakas MC.. Curr Treat Options Neurol. 2009;11(2):102-10. doi: 10.1007/s11940-009-0013-9.
3. Newsome SD and Johnson T. J Neuroimmunol. 2022;369:577915. doi: 10.1016/j.jneuroim.2022.577915.
4. Ortiz JF et al. Cureus. 2020;12(12):e11995. doi: 10.7759/cureus.11995.
5. Dalakas CD. Neurol Neuroimmunol Neuroinflamm. 2023;10(3):e200109. doi: 10.1212/NXI.0000000000200109.
When, in 2022, singer and international celebrity Celine Dion announced what she called her “one-in-a-million diagnosis” of stiff person syndrome, clinicians and medical scientists who specialize in the disorder took a deep breath. Scott D. Newsome, DO, professor of neurology and director of the Johns Hopkins Stiff Person Syndrome Center, Baltimore – a glass-half-full kind of person – saw in Ms. Dion’s worrying announcement a huge opportunity nonetheless: To raise awareness about the rare cluster of disorders known collectively as stiff person spectrum disorders (SPSD).
“Even at the clinician level, if you don’t know the hallmark signs and symptoms, you could possibly misdiagnose it,” Dr. Newsome said in an interview.
But misdiagnosis can go either way; increased awareness of SPSD can have a downside. Thirty years ago, when Marinos C. Dalakas, MD, first began studying SPSD, the diagnosis was frequently missed – “because people were not aware of it,” he said. But now, Dr. Dalakas, professor of neurology and director of the division of neuromuscular diseases in the department of neurology at Thomas Jefferson University and the Jefferson Hospital for Neuroscience, both in Philadelphia, said overdiagnosis is also a concern, particularly with increased public awareness.
“Just this last month I saw two patients who told me: ‘I read about it, and I believe I have symptoms of stiff person,’ ” he said.
These days, most patients in whom SPSD is suspected end up with an alternate diagnosis. In a recent retrospective study that Dr. Dalakas coauthored, of 173 patients who had been referred to the Mayo Clinic in Rochester, Minn., with suspected SPSD,1 Dr. Dalakas and colleagues determined that only 48 (27.7%) actually had the disorder – meaning that the rest might have been unnecessarily exposed to immunosuppressive SPSD therapies and that treatment for their actual disorder (most often, a functional neurologic disorder or nonneurologic condition) was delayed.
At the root of both underdiagnosis and overdiagnosis of SPSD is the heterogeneity of the condition and a lack of definitive diagnostic markers.
SPSD has been considered an autoimmune disorder for a long time, and observations by Dr. Dalakas and others have shown that as many as 35% of cases co-occur with another autoimmune disease, such as vitiligo, celiac disease, rheumatologic disease, type 1 diabetes mellitus, and thyroid disease (Grave’s disease and Hashimoto’s thyroiditis).2 A more recent study by his group observed an even higher rate (42%) of comorbid autoimmunity, with autoimmune thyroid disease being most common. However, although most cases of SPDS are characterized by an elevated level of glutamic acid decarboxylase (GAD)65-IgG, these autoantibodies are not specific to SPSD (low levels are also seen in diabetes, thyroid disease, healthy controls, etc.). Some SPSD patients have less common autoantibodies and a minority has no autoantibodies. Dr. Newsome said seronegative cases and the antibody presence and titers not being associated with disease severity or treatment response are clues that “SPSD does not appear to be a primary antibody-mediated condition and that there must be other immune factors at play.”
Autoimmune process drives SPSD
Autoimmunity, even if not detected by serologic studies, is believed to inhibit expression of gamma aminobutyric acid (GABA) receptors, which, in turn, results in stiffness and spasms. Although what are known as “Dalakas criteria,” proposed in 2009,2 describe the “classic” SPSD phenotype, encompassing roughly three-quarters of SPSD patients, there have now been other phenotypes proposed under SPSD, including isolated forms (stiff limb or trunk syndrome) and “nonclassic” phenotypes like SPS-plus (classic features plus brain stem and/or cerebellar involvement),3 overlap syndromes (for example, classic features with refractory epilepsy/limbic encephalitis), and probably the most severe phenotype, progressive encephalomyelitis with rigidity and myoclonus.
Early and aggressive therapy with benzodiazepines and other GABA-ergic agonists, as well as immune-based treatments, is considered critical to slowing progression of SPSD. However, the insidious onset of what is often a cluster of vague, nonspecific symptoms is a challenge for clinicians to recognize.
“When a patient comes in with muscular spasms, with stiffness in the back, in the legs, and it’s unexplained and it’s not due to spinal cord disease, or multiple sclerosis ... think SPSD,” said Dr. Dalakas. “Check antibodies – that’s the first thing to do.”
Antibody positivity is most helpful at high levels, he added; low titers can be present in autoimmune diabetes and other conditions, as previously mentioned. The real challenge? When a patient is seronegative.
Embarking on a diagnostic odyssey
Patients “bounce from one clinician to the next looking for answers,” said Dr. Newsome. “Patients will often start with their general practitioner and be referred to physical therapy, rheumatology, or orthopedics, and other specialists, which could include neurology and/or psychiatry, among others. SPSD is often not considered as a possible diagnosis until the patient develops more concrete symptoms and/or objective signs on exam. Of course, considering this diagnosis starts at knowing that it exists.”
Task-specific phobias and exaggerated acoustic startle or sensory reflex are specific symptoms that can red-flag some SPSD patients, said Dr. Dalakas. “Impaired GABA is also important for fears and anxiety. So, when you have a reduction of GABA you have more phobic neuroses – fear of crossing the street, fear of speaking in public, and they get very tense and they cannot perform.
“If the GABA-ergic pathways are dysfunctional, then there’s a relative hyper-excitability within the nervous system,” said Dr. Newsome. “This can be evaluated with electromyography. “The muscles are unhinged and going crazy: Agonists and antagonists are contracting together, which is abnormal. We will also assess for continuous motor unit potential activity within individual muscles – angry muscles just continuously firing. In our experience, this finding appears to be a pretty specific sign of SPS, especially in the torso.” Importantly, the sudden contraction of muscles along with stiffness can lead to traumatic falls, causing major orthopedic and brain injury.
In early stages of SPSD, a careful history and clinical exam is critical to try to shorten what Dr. Newsome calls the patient’s “diagnostic odyssey.”
“It behooves the clinician to put their hands on the patient. Check their back, their abdomen – try to feel for rigidity, paraspinal muscle spasms, and tightness. These regions of the body often have a ropey feel to them, which is due to chronic muscle spasms and tightness. Most [SPSD] patients will have this present in the thoracolumbar area,” he explained. “Check for hyperlordosis, as this is a hallmark sign on exam in SPSD. Additionally, patients can have rigidity and spasticity in their legs or arms. Also, patients with nonclassical phenotypes can present with a variety of other symptoms and findings on exam, including ataxia, nystagmus, ophthalmoparesis, and dysarthria.”
Lumbar puncture can sometimes reveal signs of inflammation, such as an elevated white blood cell count and oligoclonal bands in spinal fluid.
“The classic teaching was that you can only see such findings in conditions like multiple sclerosis, but that’s not the case,” said Dr. Newsome. “You can see these findings in other autoimmune conditions, including SPSD. Hence, as part of the workup, we will have patients undergo lumbar punctures to assess for these markers of autoimmunity.”
Other mimics of SPSD, including multiple sclerosis, tumors, and spinal stenosis, should be ruled out with MRI of the brain and spine.
Treatment options
Because of wide variability in signs and symptoms of the disorder, treatment of SPSD is a highly individualized cocktail of interventions, which might include immunotherapy and GABA-ergic agonists, as well as nonmedication treatments. The response to these agents can be difficult to quantify.
Benzodiazepines (diazepam, clonazepam, baclofen) along with other oral symptomatic treatments are often recommended as first-line therapy because of their ability to enhance GABA.4
First-line immunotherapy is usually intravenous immunoglobulin, steroids, or plasmapheresis. Second- and third-line agents include rituximab, mycophenolate mofetil, azathioprine, cyclophosphamide, and combination immune treatments.
Dr. Newsome and Dr. Dalakas have independently published a step-by-step therapeutic approach to SPSD.3,5 But in patients with paraneoplastic stiff person syndrome, eradication of their cancer is critical, although, per Dr. Newsome, “this does not always cure SPS and most of these patients still have residual disability.”
But immune-based therapies are only part of what should be a multipronged treatment approach, said Dr. Newsome. He also strongly advocates for non-pharmacological interventions, such as selective physical therapy (stretching, ultrasound, and gait and balance training), heat therapy, aquatherapy, deep-tissue massage or myofascial techniques, osteopathic or chiropractic manipulation, acupuncture, and acupressure.3
Because SPSD is considered a progressive disorder for some, a reasonable goal of treatment is to prevent worsening, said Dr. Newsome. This can take time: “We don’t expect the treatments to work overnight. It involves consecutive months and, sometimes, a couple of years of immune treatment before you start to see it impact the person’s life favorably.”
Patients who are not well informed about the long-term goal of treatments might be tempted to abandon the treatments prematurely because they don’t see immediate results, Dr. Newsome added. Encouraging realistic expectations is also important, without dashing hopes.
“I have patients who were marathon runners, and they want to get back to doing marathons. I would love nothing more than for people to get back to their pre-SPSD levels of function. But this may not be a realistic goal. However, this does not mean that quality of life can’t be helped.”
Nevertheless, Dr. Newsome encourages clinicians to reassess regularly, especially because lack of disease biomarkers makes it hard to objectively monitor the impact of therapy.
“It’s always a good rule of thumb, especially in the rare disease space, to step back and ask: ‘Are we on the right treatment path or not?’ If we’re not, then it is important to make sure you have the correct diagnosis. Even when you have a patient who fits the textbook and you, yourself, diagnosed them, it is important to continue to re-evaluate the diagnosis over time, especially if there is consideration of changing treatments. It is also important to make sure there is not something else on top of the stiff person syndrome that is working in parallel to worsen their condition.”
Be alert for comorbidity
Undiagnosed comorbid conditions that can complicate SPSD include Parkinson’s disease or myasthenia gravis, to name a couple, which Dr. Newsome has seen more than once. “We’ve seen a few people over the years who have both SPSD and another autoimmune or degenerative neurological condition.”
Diabetes also co-occurs in approximately 30% of people with SPSD, said Dr. Dalakas. “Endocrinologists should also be aware of this connection.”
Paraneoplastic stiff person syndrome is thought to be triggered by cancer, which might not have been diagnosed, making it important to work up patients for malignancy – particularly breast cancer, small cell lung cancer, lymphoma, and thymoma, Dr. Newsome advised.
Although most cases of SPSD are diagnosed in mid-life, the disorder can occur in teenagers and the elderly.
“It’s not the first thing you think of when a 70-year-old patient comes with neck pain, so it’s missed more often, and the prognosis is worse,” Dr. Dalakas warned.
What does the future hold?
Like Dr. Newsome, Dr. Dalakas is encouraged when SPSD hits the headlines because, generally, awareness facilitates diagnosis and research. (Both clinicians serve on the medical advisory board of The Stiff Person Syndrome Research Foundation.)
“We are looking for better therapies that target immune factors,” said Dr. Dalakas. “There are several of those that are relevant, so we need to select the best immune marker that we think plays a role in the antibody production,” he said.
“There’s a lot of hope – at least I have a lot of hope for what the future holds with SPSD,” added Dr. Newsome. “More research is needed and it starts with awareness of SPSD.”
Dr. Newsome discloses that he has received consulting fees for serving on scientific advisory boards of Biogen, Genentech, Bristol Myers Squibb, EMD Serono, Jazz Pharmaceuticals, Novartis, Horizon Therapeutics, TG Therapeutics; is the study lead principal investigator for a Roche clinical trial; and has received research funding (paid directly to his employing institution) from Biogen, Roche, Lundbeck, Genentech, The Stiff Person Syndrome Research Foundation, National Multiple Sclerosis Society, U.S. Department of Defense, and Patient-Centered Outcomes Research Institute. Dr. Dalakas reports nothing relevant to disclose.
References
1. Chia NH et al. Ann Clin Transl Neurol. 2023;10(7):1083-94. doi: 10.1002/acn3.51791.
2. Dalakas MC.. Curr Treat Options Neurol. 2009;11(2):102-10. doi: 10.1007/s11940-009-0013-9.
3. Newsome SD and Johnson T. J Neuroimmunol. 2022;369:577915. doi: 10.1016/j.jneuroim.2022.577915.
4. Ortiz JF et al. Cureus. 2020;12(12):e11995. doi: 10.7759/cureus.11995.
5. Dalakas CD. Neurol Neuroimmunol Neuroinflamm. 2023;10(3):e200109. doi: 10.1212/NXI.0000000000200109.