Quantitative Assessment of Response to Long-Term Treatment with Intravenous Immunoglobulin in Patients with Stiff Person Syndrome

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.

Expanding clinical profiles and prognostic markers in stiff person syndrome spectrum disorders

OBJECTIVE

To describe the clinical features of a cohort of individuals with stiff person syndrome spectrum disorders (SPSD) and identify potential early predictors of future disability.

BACKGROUND

There is a need to better understand the full spectrum of clinical and paraclinical features and long-term impact of SPSD.

DESIGN/METHODS

Observational study from 1997 to 2022 at Johns Hopkins. Clinical phenotypes included classic SPS, partial SPS (limb or trunk limited), SPS-plus (classic features plus cerebellar/brainstem involvement), and progressive encephalomyelitis with rigidity and myoclonus (PERM). Outcome measures were modified Rankin scale (mRS) and use of assistive device for ambulation. Multivariate logistic regression was used to assess significant predictors of outcomes.

RESULTS

Cohort included 227 individuals with SPSD with mean follow-up of 10 years; 154 classic, 48 SPS-plus, 16 PERM, and 9 partial. Mean age at symptom onset was 42.9 ± 14.1 years, majority were white (69.2%) and female (75.8%). Median time to diagnosis was 36.2 months (longest for SPS-plus and PERM) and 61.2% were initially misdiagnosed. Most had systemic co-morbidities and required assistive devices for ambulation. Female sex (OR 2.08; CI 1.06-4.11) and initial brainstem/cerebellar involvement (OR 4.41; CI 1.63-14.33) predicted worse outcome by mRS. Older age at symptom onset (OR 1.04; CI 1.01-1.06), female sex (OR 1.99; CI 1.01-4.01), Black race (OR 4.14; CI 1.79-10.63), and initial brainstem/cerebellar involvement (OR 2.44; CI 1.04-7.19) predicted worse outcome by use of assistive device. Early implementation of immunotherapy was associated with better outcomes by either mRS (OR 0.45; CI 0.22-0.92) or use of assistive device (OR 0.79; CI 0.66-0.94).

CONCLUSIONS

We present the expanding phenotypic variability of this rare spectrum of disorders and highlight potential predictors of future disability.

Intravenous immunoglobulin in the management and outcome of Stiff‐Person syndrome: A systematic review

Background

Stiff Person Syndrome (SPS), a rare immune‐mediated neuromuscular disorder, is characterized by rigidity, stiffness, and intermittent spasms of axial and extremity muscles. Various immunotherapies including intravenous immunoglobulin (IVIG) have been used for this autoimmune condition. Here we aim to review the role of IVIG in the treatment of SPS along with its outcome.

Methods

A systematic literature search of PubMed and Embase was conducted to identify the relevant published articles against the predefined criteria using suitable keywords combinations till September 20, 2021. Data were extracted to produce descriptive information of SPS patients on demographics, diagnostics, treatment with IVIG, and outcome.

Results

Twelve studies with 216 patients were included in the review and 63.89% of them had classical SPS. Glutamic acid decarboxylase (GAD) autoantibodies were present in 72.68% of the patients and 57.89% in whom electromyography (EMG) was performed had continuous motor activity. IVIG therapy was given to 95 patients in different regimens in various studies and varying scoring systems were used to assess the outcome, and 83.16% showed some form of improvement, 14.74% showed no improvement, while 2.10% worsened. None of the included studies mentioned an adverse effect of IVIG in the patients.

Conclusion

IVIG may benefit patients with SPS along with other medications. Owing to the rarity of the disease and insufficient studies on the assessment of immunotherapy in SPS, longitudinal studies with a sizable number of patients are required to clarify clinical course, treatment, and outcome in SPS with the use of IVIG.

Long-term Effectiveness of IVIg Maintenance Therapy in 36 Patients With GAD Antibody–Positive Stiff-Person Syndrome

Background and Objectives

IVIg has been the preferred immunotherapy in stiff-person syndrome (SPS) based on a 3-month controlled trial, but whether it is also effective in inducing long-term benefits or arresting disease progression is unknown. The information is needed because SPS is a progressively disabling disease and IVIg is liberally used as chronic therapy without efficacy data. The present study explores the long-term effects of IVIg in the largest cohort of well-characterized patients with SPS followed by the same clinicians over 10 years.

Methods

Data of 36 patients (32 glutamic acid decarboxylase [GAD] positive), diagnosed and treated with monthly maintenance IVIg by the same neurologists, were analyzed. Response was assessed by physician-observed changes, patients' reports of symptom improvement, modified Rankin Scale (mRS) scores, and dependency trials evaluating symptom recurrence after stopping IVIg, prolonging infusion frequency, decreasing monthly dose, or wearing-off effects in between doses. Clinically meaningful long-term response was defined by improved mRS scores, improvement in physician-assessed stiffness, balance and gait, and functional decline with dependency trials.

Results

Twenty-four of 36 (67%) patients had clinically meaningful response over a median 40-month period. Patients with improved mRS scores by 1–2 points manifested improved gait, posture, balance and decreased stiffness, spasms, and startle response; some patients using a wheelchair and those ambulating with devices walked unassisted. In 25% of responders, treatment benefit was sustained for a 40-month median period, but in 29.1%, it declined over a 39-month period; 12.5% exhibited a conditioning effect. Three of 5 patients with cerebellar GAD-SPS variant also improved over time. The 12 patients who did not respond the first 3 months remained unresponsive even if IVIg continued for several months.

Discussion

This is a large study in 36 patients with SPS demonstrating that monthly maintenance IVIg therapy offers long-term benefits in 67% of patients for a median 3.3-year period. Because 29.1% experienced diminishing benefit over time due to disease progression, the study highlights the need for more effective therapies.

One in a Million: A Case Report of Stiff Person Syndrome

Stiff person syndrome (SPS) is a rare autoimmune disease caused by lack of inhibition to excitatory neurotransmitters in the central nervous system (CNS) leading to inappropriate motor unit firing. The pathophysiology is incompletely understood; however, high titers of antiglutamic acid decarboxylase antibody (anti-GAD Ab) are strongly associated with this disease. We present a 50-year-old woman with a history of ongoing gait and balance issues for 5 years with multiple negative workups. She recently had an acute exacerbation which left her bedbound, unable to move her legs or turn from side to side. After a negative workup at an outside hospital, the patient was discharged to a subacute rehabilitation facility. She then presented to our institution due to worsening of her condition and was ultimately diagnosed with SPS which was successfully treated. We review the case presentation and treatment options in the context of a severe disabling disease presentation.