Stiff-person syndrome: autoimmunity and the central nervous system

Physical therapist management of stiff person syndrome in a 24-year-old woman

BACKGROUND AND PURPOSE

Stiff person syndrome is a rare neurological disorder characterized by stiffness and painful spasms primarily in the trunk and lower extremities. The role of physical therapy in the management of this disorder is disputed and the efficacy of specific interventions is unknown.

CASE DESCRIPTION

The patient was a 24-year-old woman with a 1-year history of stiff person syndrome who received outpatient physical therapy over the course of 15 weeks. She had pain, muscle spasms, gait anomalies, and range-of-motion deficits, which affected her left lower extremity. Physical therapy interventions consisted of ultrasound, soft tissue mobilizations, manual stretching, and exercise. She also was fitted for a custom-made ankle-foot orthosis. Outcome This patient showed decreased pain and muscle spasms, as well as improvements in gait and range of motion.

DISCUSSION

Stiffness and spasms interfere with the ability of these patients to fully mobilize affected joints, and they are at risk of developing further complications. Physical therapy may have a role in the management of this disease, as these patients need to be taught how to properly stretch and maintain joint mobility as a lifelong commitment.

Stiff person syndrome: advances in pathogenesis and therapeutic interventions

Stiff person syndrome (SPS) varies from mild to severe, but if untreated it can be progressive and disabling. Although progress has been made in understanding and treating SPS, the disease remains underdiagnosed, delaying treatment. Antibodies against glutamic acid decarboxylase provide an excellent diagnostic marker, but their role in disease pathogenesis is uncertain. Research focused on identifying new autoantigens has provided evidence that gamma-aminobutyric acid (GABA)(A) receptor-associated protein (GABARAP), a 14-kD protein localized at the postsynaptic regions of GABAergic synapses, is an antigenic target. Circulating anti-GABARAP antibodies that inhibit GABA(A) receptor expression on GABAergic neurons have been found in up to 65% of SPS patients. The impairment of GABAergic pathways and reduction of brain GABA results in clinical manifestations of stiffness, spasms, and phobias. Increased awareness of SPS among practicing physicians is necessary to recognize the disease early and prevent permanent disability. Most patients with SPS respond to GABA-enhancing drugs, but the high doses required cause unacceptable adverse effects. The disease clearly responds to intravenous immunoglobulin, but repeated infusions are needed to maintain response. New immunomodulating agents are being explored to treat difficult cases and to induce long-lasting remissions.

Human stiff-person syndrome IgG induces anxious behavior in rats

Background

Anxiety is a heterogeneous behavioral domain playing a role in a variety of neuropsychiatric diseases. While anxiety is the cardinal symptom in disorders such as panic disorder, co-morbid anxious behavior can occur in a variety of diseases. Stiff person syndrome (SPS) is a CNS disorder characterized by increased muscle tone and prominent agoraphobia and anxiety. Most patients have high-titer antibodies against glutamate decarboxylase (GAD) 65. The pathogenic role of these autoantibodies is unclear.

Methodology/Principal Findings

We re-investigated a 53 year old woman with SPS and profound anxiety for GABA-A receptor binding in the amygdala with (11)C-flumazenil PET scan and studied the potential pathogenic role of purified IgG from her plasma filtrates containing high-titer antibodies against GAD 65. We passively transferred the IgG fraction intrathecally into rats and analyzed the effects using behavioral and in vivo electrophysiological methods. In cell culture, we measured the effect of patient IgG on GABA release from hippocampal neurons. Repetitive intrathecal application of purified patient IgG in rats resulted in an anxious phenotype resembling the core symptoms of the patient. Patient IgG selectively bound to rat amygdala, hippocampus, and frontal cortical areas. In cultured rat hippocampal neurons, patient IgG inhibited GABA release. In line with these experimental results, the GABA-A receptor binding potential was reduced in the patient's amygdala/hippocampus complex. No motor abnormalities were found in recipient rats.

Conclusion/Significance

The observations in rats after passive transfer lead us to propose that anxiety-like behavior can be induced in rats by passive transfer of IgG from a SPS patient positive for anti-GAD 65 antibodies. Anxiety, in this case, thus may be an antibody-mediated phenomenon with consecutive disturbance of GABAergic signaling in the amygdala region.

Stiff person syndrome-associated autoantibodies to amphiphysin mediate reduced GABAergic inhibition

Synaptic inhibition is a central factor in the fine tuning of neuronal activity in the central nervous system. Symptoms consistent with reduced inhibition such as stiffness, spasms and anxiety occur in paraneoplastic stiff person syndrome with autoantibodies against the intracellular synaptic protein amphiphysin. Here we show that intrathecal application of purified anti-amphiphysin immunoglobulin G antibodies induces stiff person syndrome-like symptoms in rats, including stiffness and muscle spasms. Using in vivo recordings of Hoffmann reflexes and dorsal root potentials, we identified reduced presynaptic GABAergic inhibition as an underlying mechanism. Anti-amphiphysin immunoglobulin G was internalized into neurons by an epitope-specific mechanism and colocalized in vivo with presynaptic vesicular proteins, as shown by stimulation emission depletion microscopy. Neurons from amphiphysin deficient mice that did not internalize the immunoglobulin provided additional evidence of the specificity in antibody uptake. GABAergic synapses appeared more vulnerable than glutamatergic synapses to defective endocytosis induced by anti-amphiphysin immunoglobulin G, as shown by increased clustering of the endocytic protein AP180 and by defective loading of FM 1-43, a styryl dye used to label cell membranes. Incubation of cultured neurons with anti-amphiphysin immunoglobulin G reduced basal and stimulated release of γ-aminobutyric acid substantially more than that of glutamate. By whole-cell patch-clamp analysis of GABAergic inhibitory transmission in hippocampus granule cells we showed a faster, activity-dependent decrease of the amplitude of evoked inhibitory postsynaptic currents in brain slices treated with antibodies against amphiphysin. We suggest that these findings may explain the pathophysiology of the core signs of stiff person syndrome at the molecular level and show that autoantibodies can alter the function of inhibitory synapses in vivo upon binding to an intraneuronal key protein by disturbing vesicular endocytosis.

Advances in the pathogenesis and treatment of patients with stiff person syndrome

Advances in the clinical diagnosis, prognosis, pathogenesis, and therapies for stiff person syndrome (SPS), based on observations in more than 50 consecutive patients, are presented. The syndrome varies from mild to severe, but if untreated it can be progressive and disabling. SPS remains a largely underdiagnosed condition. Anti-glutamic acid decarboxylase (GAD) antibodies provide an excellent diagnostic marker, but their role in disease pathogenesis is uncertain. Research focused on identifying new autoantigens has provided evidence that gamma-aminobutyric acid (GABA)(A) receptor-associated protein (GABARAP), a 14-kD protein localized at the postsynaptic regions of GABAergic synapses, is a new antigenic target. In up to 65% of SPS patients, there are circulating anti-GABARAP antibodies that inhibit the GABA(A) receptor expression on GABAergic neurons. This review examines the diagnostic criteria for SPS, SPS variants, common errors in diagnosis, and a step-by-step therapeutic approach, including new advances in therapy.

Rigidity and spasms from autoimmune encephalomyelopathies: stiff-person syndrome

Stiff-person syndrome (SPS) is a disorder characterized by progressive muscle rigidity with superimposed painful muscle spasms and gait impairment due to continuous motor activity. Evidence has accumulated in favor of SPS representing an autoimmune, predominantly encephalomyelopathic disorder resulting from B-cell-mediated clonal production of autoantibodies against presynaptic inhibitory epitopes on the enzyme glutamic acid decarboxylase (GAD) and the synaptic membrane protein amphiphysin. Recognition of the clinical spectrum of SPS is important, particularly the upper-limb, cervical, and cranial nerve involvement that occurs in paraneoplastic variants. The correlation between antibody levels and severity of disease offers evidence for a pathogenic role for the anti-GAD and anti-amphiphysin autoantibodies. The scarcity of neuropathological correlates stand in sharp contrast with the severity of the disability in affected individuals and suggests that functional impairment of inhibitory circuits without structural damage is sufficient to develop the full clinical spectrum of SPS. The rarity of this condition limits the feasibility of controlled clinical trials in the treatment of SPS, but the available evidence suggest that drugs that increase cortical and spinal inhibition such as benzodiazepines and drugs that provide immune modulation such as intravenous immunoglobulin, plasmapheresis, and prednisone are effective treatments.

Intravenous immunoglobulin therapy in paraneoplastic neurological syndromes

Combining clinical and immunological information, a neurological syndrome can now be diagnosed as a "definite" or "possible" paraneoplastic syndrome according to the newly suggested diagnostic criteria of the PNS Euronetwork. Differentiated diagnosis of a paraneoplastic syndrome is essential for differential therapy in patients. According to the response to IVIG therapy, paraneoplastic disorders may be subgrouped in group A, a clinical response is the rule (prototype Lambert-Eaton myasthenic syndrome), and in group B, IVIG may be helpful in single patients and is indicated in specific clinical settings (prototype anti-Hu associated neurological syndromes). The mode of action of IVIG may range from direct anti-idiotype effect to indirect effects on the cellular part of the pathogenesis of paraneoplastic syndromes. Due to the therapeutic relevance, it is therefore important to diagnose a PND as early as possible, and start immunotherapy including IVIG immediately.

Stiff-Person Syndrome

BACKGROUND

Stiff-person syndrome (SPS) is a rare neurologic disorder with autoimmune features. It is characterized by progressive, severe muscle rigidity or stiffness most prominently affecting the spine and lower extremities.

REVIEW SUMMARY

Superimposed muscle spasms result in simultaneous contraction of agonist and antagonist muscles which are detectable by electromyography (EMG) and relieved by administration of benzodiazepines. The exacerbation of SPS by emotional stressors often results in the referral of these patients for psychiatric assessment although this was more common before the discovery of an association with antibodies to glutamic acid decarboxylase (GAD antibodies). Formerly known as stiff-man syndrome, the female to male ratio is 2:1 and the principle paraneoplastic variant is associated with breast cancer. Although rare, this is a disease of middle age that severely curtails the functional capacity of those it strikes. It is frequently associated with diabetes and other autoimmune diseases. IVIg is recently demonstrated to be effective in the treatment of SPS; diazepam remains useful in managing the symptoms.

CONCLUSIONS

This article summarizes the history of SPS, describes important clinical features, discusses management, touches upon areas of uncertainty, and postulates some avenues for research.