Stiff person spectrum disorder diagnosis, misdiagnosis, and suggested diagnostic criteria

Stiff-person syndrome and related disorders - diagnosis, mechanisms and therapies

Stiff-person syndrome (SPS) is the prototypical and most common autoimmune neuronal hyperexcitability disorder. It presents with stiffness in the limbs and axial muscles, stiff gait with uncontrolled falls, and episodic painful muscle spasms triggered by anxiety, task-specific phobias and startle responses, collectively leading to disability. Increased awareness of SPS among patients and physicians has created concerns about diagnosis, misdiagnosis and treatment. This Review addresses the evolving diagnostic challenges in SPS and overlapping glutamic acid decarboxylase (GAD) antibody spectrum disorders, highlighting the growing number of overdiagnoses and focusing on the progress made in our understanding of SPS pathophysiology, antibodies against GAD and other inhibitory synaptic antigens, and the fundamentals of neuronal hyperexcitability. It considers the role of impaired GABAergic or glycinergic inhibition in the cortex and at multiple levels in the neuraxis; the underlying autoimmunity and involvement of GAD antibodies; immunopathogenic mechanisms beyond antibodies, including environmental triggers; familial and immunogenetic susceptibility; and potential T cell cytotoxicity. Finally, the mechanistic rationale for target-specific therapeutic interventions is presented along with the available therapeutic approaches, including enhancers of GABA signalling drugs and immunotherapies.

Stiff-person syndrome

Stiff-person syndrome (SPS) is an autoimmune disease associated mainly with antibodies to glutamic acid decarboxylase (GAD) or to glycine, characterised by intermittent painful spasms, stiffness and rigidity of the proximal and truncal muscles. Neuro-ophthalmological and gastrointestinal symptoms also occur. The symptoms are caused by neuronal excitability due to impaired inhibitory (gamma amino butyric acid [GABA] and glycine) neurotransmission. SPS is part of a larger spectrum of GAD antibody-spectrum disorders, which overlaps with autoimmune epilepsy, cerebellar ataxia, myoclonus, progressive encephalomyelitis, rigidity and myoclonus (PERM) and limbic encephalitis. PERM is often caused by antibodies against the glycine receptor. Some SPS cases are paraneoplastic. Diagnostic delay is often associated with irreversible disability, and therefore, clinicians need a high degree of clinical suspicion to make an earlier diagnosis. This review updates the various clinical presentations that should raise suspicion of SPS and its related conditions and includes a diagnostic algorithm and various treatment strategies including immunotherapy and GABA-ergic drugs.

Stiff Person Syndrome and GAD Antibody-Spectrum Disorders

OBJECTIVE

Antibodies against glutamic acid decarboxylase (GAD), originally associated with stiff person syndrome (SPS), define the GAD antibody-spectrum disorders that also include cerebellar ataxia, autoimmune epilepsy, limbic encephalitis, progressive encephalomyelitis with rigidity and myoclonus (PERM), and eye movement disorders, all of which are characterized by autoimmune neuronal excitability. This article elaborates on the diagnostic criteria for SPS and SPS spectrum disorders, highlights disease mimics and misdiagnoses, describes the electrophysiologic mechanisms and underlying autoimmunity of stiffness and spasms, and provides a step-by-step therapeutic scheme.

LATEST DEVELOPMENTS

Very-high serum GAD antibody titers are diagnostic for GAD antibody-spectrum disorders and also predict the presence of GAD antibodies in the CSF, increased intrathecal synthesis, and reduced CSF γ-aminobutyric acid (GABA) levels. Low serum GAD antibody titers or the absence of antibodies generates diagnostic challenges that require careful distinction in patients with a variety of painful spasms and stiffness, including functional neurologic disorders. Antibodies against glycine receptors, first found in patients with PERM, are seen in 13% to 15% of patients with SPS, whereas amphiphysin and gephyrin antibodies, seen in 5% of patients with SPS spectrum disorders, predict a paraneoplastic association. GAD-IgG from different SPS spectrum disorders recognizes the same dominant GAD intracellular epitope and, although the pathogenicity is unclear, is an excellent diagnostic marker. The biological basis of muscle stiffness and spasms is related to autoimmune neuronal hyperexcitability caused by impaired reciprocal γ-aminobutyric acid-mediated (GABA-ergic) inhibition, which explains the therapeutic response to GABA-enhancing agents and immunotherapies.

ESSENTIAL POINTS

It is essential to distinguish SPS spectrum disorders from disease mimics to avoid both overdiagnoses and misdiagnoses, considering that SPS is treatable if managed correctly from the outset to prevent disease progression. A step-by-step, combination therapy of GABA-enhancing medications along with immunotherapies ensures prolonged clinical benefits.

Stiff-person syndrome in association with Hashimoto's thyroiditis: a case report

Stiff-person syndrome (SPS) is a rare neurological disorder characterized by chronic and progressive axial muscle rigidity and paroxysmal painful muscle spasms. The present case study described an SPS patient (increased anti-GAD65 antibody in serum and cerebrospinal fluid) with co-occurring Hashimoto's thyroiditis and decreased C3 complement levels. The clinical presentation, diagnostic approach, and treatment employed for this unique case were comprehensively described in detail. In this case, we comprehensively presented a case of SPS with co-occurring Hashimoto's thyroiditis and an associated decrease in serum C3 complement, as well as a discussion on the current data on this topic.

Efficacy and Safety of Rescue Treatment with Plasma Exchange in Patients with Acute Inflammatory Neurological Disorders: A Single Center Experience

BACKGROUND

Therapeutic plasma exchange (TPE) is a highly effective rescue treatment for patients with acute exacerbation of neuroimmunological disease that removes circulating autoantibodies and inflammatory components from the bloodstream. The aims of this study are to explore the safety and the effectiveness of TPE in patients with autoimmune neurological disorders.

METHODS

We retrospectively evaluated the frequency of adverse events (AEs) and the effectiveness of TPE using the modified Ranking Scale (mRS) in patients with acute neurological flares who underwent TPE at the University Hospital of Palermo.

RESULTS

Of 59 patients, the majority underwent TPE due to multiple sclerosis (MS) relapse. In 23.7% of cases, TPE was performed before obtaining a definite diagnosis due to the severity of the clinical presentation. After TPE, the mRS score was globally reduced (p < 0.0001), and this effect was marked in patients with MS, Guillain-Barré syndrome, and myasthenia gravis crisis but not in those with paraneoplastic syndromes. Circulating pathogenetic antibodies, younger age, and the early use of TPE were factors strongly associated with TPE effectiveness. The overall safety profile of TPE was satisfactory with an AE frequency of 15%.

CONCLUSIONS

These results highlight the early use of TPE in patients with circulating pathogenetic antibodies as well as its favorable safety profile.

Lessons in clinical reasoning - pitfalls, myths, and pearls: a woman brought to a halt

OBJECTIVES

Limitations in human cognition commonly result in clinical reasoning failures that can lead to diagnostic errors. A metacognitive structured reflection on what clinical findings fit and/or do not fit with a diagnosis, as well as how discordance of data can help advance the reasoning process, may reduce such errors.

CASE PRESENTATION

A 60-year-old woman with Hashimoto thyroiditis, diabetes, and generalized anxiety disorder presented with diffuse arthralgias and myalgias. She had been evaluated by physicians of various specialties and undergone multiple modalities of imaging, as well as a electromyography/nerve conduction study (EMG/NCS), leading to diagnoses of fibromyalgia, osteoarthritis, and lumbosacral plexopathy. Despite treatment for these conditions, she experienced persistent functional decline. The only definitive alleviation of her symptoms identified was in the few days following intra-articular steroid injections for osteoarthritis. On presentation to our institution, she appeared fit with a normal BMI. She was a long-time athlete and had been training consistently until her symptoms began. Prediabetes had been diagnosed the year prior and her A1c progressed despite lifestyle modifications and 10 pounds of intentional weight loss. She reported fatigue, intermittent nausea without emesis, and reduced appetite. Examination revealed intact strength and range of motion in both the shoulders and hips, though testing elicited pain. She had symmetric hyperreflexia as well as a slowed, rigid gait. Autoantibody testing revealed strongly positive serum GAD-65 antibodies which were confirmed in the CSF. A diagnosis of stiff-person syndrome was made. She had an incomplete response to first-line therapy with high-dose benzodiazepines. IVIg was initiated with excellent response and symptom resolution.

CONCLUSIONS

Through integrated commentary on the diagnostic reasoning process from clinical reasoning experts, this case underscores the importance of frequent assessment of fit along with explicit explanation of dissonant features in order to avoid misdiagnosis and halt diagnostic inertia. A fishbone diagram is provided to visually demonstrate the major factors that contributed to the diagnostic error. The case discussant demonstrates the power of iterative reasoning, case progression without commitment to a single diagnosis, and the dangers of both explicit and implicit bias. Finally, this case provides clinical teaching points in addition to a pitfall, myth, and pearl specific to overcoming diagnostic inertia.

[Stiff-person syndrome]

Stiff-person syndrome is a rare autoimmune disorder manifested by stiffness in the trunk and proximal limb muscles and painful muscle spasms in them. The disease is associated with the production of glutamate decarboxylase autoantibodies, an enzyme converting glutamate into gamma-aminobutyric acid. An increase of anti-GAD antibody serum levels above 10.000 IU/mL is specific for stiff-person syndrome. Our own clinical observation of a patient diagnosed with stiff-person syndrome is presented.

Late-onset stiff-person syndrome: challenges in diagnosis and management

Background

Stiff person syndrome (SPS) is a rare slowly progressive autoimmune neuronal hyperexcitability disease with very-high GAD-65 antibody titers that most commonly presents above the age of 20, with muscle stiffness, painful muscle spasms, slow gait, and falls leading to disability. In other autoimmune disorders, late-onset disease has different symptom-spectrum and outcomes, but there is no information regarding late-onset SPS (LOSPS).

Objective

Highlight delayed diagnosis and poor tolerance or incomplete response to therapies of patients with LOSPS and outline how best to increase disease awareness early at onset.

Design A retrospective chart reviewMethods

We reviewed GAD-positive SPS patients with symptom onset above age 60, identified among 54 SPS patients, examined, treated and followed-up by the same clinicians, focused on clinical presentation, misdiagnoses, response and tolerance to therapies, and evolved disability.

Results

Nine patients had LOSPS with symptom onset at median age of 61 years (range 60-78), and current median age of 73. The median time from symptom onset to SPS diagnosis was 3 years; prior to diagnosis, five patients were treated for lumbosacral radiculopathies (one with laminectomy), two for Parkinson's disease, one for multiple sclerosis, and another for cerebellar degeneration. Progressive decline occurred rapidly in all patients; at time of diagnosis, six patients were already using a cane or walker and two were wheelchair-bound. Tolerance and response to treatment were limited; two patients did not respond to IVIg, two discontinued IVIg despite early response due to comorbidities (cardiac disease, thrombosis), four others partially responded to IVIg and one to rituximab; several could not tolerate high doses of oral antispasmodics due to somnolence; and two patients died.

Conclusions

LOSPS is almost always misdiagnosed for other similar conditions commonly seen in the elderly. Patients with LOSPS decline quickly to clinically severe disease due to delayed treatment initiation, poor response or tolerance, other comorbidities, and possibly immunosenescence. Increased awareness that SPS can occur in the elderly mimicking other disorders is important for early diagnosis and treatment, even necessitating earlier immunotherapy initiation, compared to their younger counterparts, to prevent faster-evolving severe disability.

Stiff Person Spectrum Disorders-An Update and Outlook on Clinical, Pathophysiological and Treatment Perspectives

Stiff person spectrum disorders (SPSD) are paradigm autoimmune movement disorders characterized by stiffness, spasms and hyperekplexia. Though rare, SPSD represent a not-to-miss diagnosis because of the associated disease burden and treatment implications. After decades as an enigmatic orphan disease, major advances in our understanding of the evolving spectrum of diseases have been made along with the identification of multiple associated autoantibodies. However, the most important recent developments relate to the recognition of a wider affection, beyond the classic core motor symptoms, and to further insights into immunomodulatory and symptomatic therapies. In this review, we summarize the recent literature on the clinical and paraclinical spectrum, current pathophysiological understanding, as well as current and possibly future therapeutic strategies.