Understanding stiff-person syndrome: Epidemiological trends, diagnostic challenges, and treatment advances.

Stiff-person syndrome spectrum disorders (SPSD) comprise a group of rare neuroimmunological conditions characterized by fluctuating muscle stiffness, painful spasms, gait disturbance, and hypersensitivity triggers. Emerging phenotypes, including posterior fossa dysfunction, highlight the heterogeneity of the spectrum. Although historically described as a "one-in-a-million" disorder, recent epidemiologic data suggest that SPSD is more common than previously recognized. Currently, consensus diagnostic criteria do not exist; however, proposed criteria emphasize key clinical findings, high titers of recognized antibodies and electrophysiology findings that help support a diagnosis. The goal of this review is to provide an overview of SPSD epidemiology with emphasis on prevalence studies, emerging diagnostic criteria and overview of the multimodal treatment approach integrating pharmacological symptomatic therapies, immunotherapy, and non-pharmacologic interventions.