P-NE014. Electromyography in the diagnosis of stiff-person syndrome

Abstract

Introduction . Stiff-person syndrome (SPS) is a rare autoimmune or paraneoplastic disorder with a wide clinical spectrum but core features of trunk and limb stiffness and muscle spasms. It is commonly associated with glutamic acid decarboxylase (GAD 65) antibody and responds to treatment with benzodiazepines and immunotherapy. We present the details of a patient with SPS and highlight the diagnostic utility of electromyography (EMG). Results . A 58-years-old man developed progressive asymmetric stiffness of both lower limbs and walking difficulty of ten months duration. Superimposed on that, he had painful spasms of lower limb which were triggered by sound or touch. On examination, he was found to have asymmetric hypertonia in both lower limbs and gait difficulty requiring the assistance of two- persons to walk. Serum GAD-65 antibody was strongly positive. He underwent electrophysiological evaluation. Nerve conduction studies were normal. Lower limb surface EMG with recording from quadriceps, hamstrings, tibialis anterior, and lateral head of gastrocnemius on the right side and quadriceps and hamstrings on the left side was performed. It showed continuous motor unit activity in agonist and antagonist muscle groups. After the administration of diazepam, the motor unit activity reduced significantly while stimulation with a loud sound led to an increased in activity. Based on these findings, he was diagnosed with SPS and treated with immunotherapy and symptomatic medications. He had significant improvement and was able to walk independently at four months of follow up. Conclusion . SPS is a rare but treatable neurological illness that can be confused with many other disorders like parkinsonism, dystonia, musculoskeletal, psychogenic, etc. EMG can provide a useful clue to the diagnosis by demonstrating characteristic continuous motor unit activity in agonist and antagonist muscles which triggered by specific stimuli and improved with diazepam.