Stiff-person Syndrome

Classic stiff-person syndrome (SPS) is a clinically diagnosed disease characterized by axial and often appendicular rigidity with lumbar hyperlordosis and painful spasms. Supportive data include increased glutamic acid decarboxylase autoantibody titers more than 20 nmol/L, a needle electromyography with continuous motor unit activity in at least one axial muscle, and normal MRI and cerebrospinal fluid studies. Variants of SPS include those with focal limb dysfunction (stiff-limb syndrome), encephalomyelitis ("SPS plus"), and those associated with paraneoplastic autoantibodies. Although the precise mechanism is unknown, an autoimmune etiology for SPS is proposed, based on its association with autoantibodies and other autoimmune diseases and its response to immunomodulatory therapy. The cornerstone of treatment consists of symptomatic care with benzodiazepines and/or baclofen. Other neuromodulators include antiepileptic medications and muscle relaxants. Continued disability despite first-line therapy should prompt consideration of agents aimed at immunomodulation and immunosuppression. Intravenous immunoglobulin is one of the few agents to be evaluated in a double-blind, randomized controlled trial. Other options include steroids, plasma exchange, and chemotherapy agents.