Stiffness, Spasms, and Frequent Falls in a 41-Year-Old Man

A 41-year-old man sought care for 3 years of right-sided muscle stiffness. He also had 5- to 10-minute episodes of severe muscle spasms. He noted development of daily episodes of sudden, severe stiffness, often triggered by unexpected stimuli (eg, a touch or loud sound). He started using a walker and stopped driving. He stopped working because of increasing difficulty with mobility and cognition. On neurologic examination, he had a Kokmen Short Test of Mental Status score of 28/38, with points lost for orientation, attention, calculation, and recall. Cranial nerve examination showed bilateral ptosis and hypometric saccadic eye movements. He had normal strength but diffuse rigidity with increased tone, most severe in the right lower extremity. Magnetic resonance imaging of the brain indicated right parietal postoperative changes (post hematoma evacuation). Electroencephalography showed dysrhythmia grade 1 over the right frontotemporal region (above the prior hematoma). Cerebrospinal fluid was inflammatory, with mildly increased protein concentration and supernumerary oligoclonal bands. Movement laboratory evaluation demonstrated an exaggerated startle and abnormal exteroceptive response consistent with central nervous system hyperexcitability. Neural-specific autoantibody testing was positive for glycine receptor α‎1 subunit-immunoglobulin G in both serum and cerebrospinal fluid. He was diagnosed with progressive encephalomyelitis with rigidity and myoclonus with positive glycine receptor α‎1 subunit-immunoglobulin G. Given the immune-mediated cause of progressive encephalomyelitis with rigidity and myoclonus, he was started on intravenous methylprednisolone and concurrent rituximab. The patient markedly improved. His anxiety was still severe, however, and required increased escitalopram and cognitive behavioral therapy to control. He was tapered off intravenous methylprednisolone and maintained on rituximab. His symptoms eventually resolved. He remained stable at 2-year follow-up after initiating immunosuppression. Progressive encephalomyelitis with rigidity and myoclonus is considered a variant of stiff-person syndrome. There is clinical overlap between progressive encephalomyelitis with rigidity and myoclonus and classic stiff-person syndrome, which are both characterized by central nervous system hyperexcitability with exaggerated startle, muscle rigidity, and painful spasms.