SPS is a rare neuroimmunological condition, classically presenting with axial and/or limb rigidity along with superimposed painful episodic spasms.

Average age at symptom onset was 42 years (range: 11-75), and the majority were Caucasian (73%) and female (73%). Mean time to diagnosis was 61 months and over 60% were initially misdiagnosed.  Over 60% had systemic co-morbidities, most commonly thyroid disorders, insulin-dependent diabetes mellitus, and pernicious anemia. Over half had co-existing psychiatric conditions. The initial symptoms in 76% of individuals were stiffness and/or spasms; limbs affected more than axial regions. Others presented with cerebellar and/or brainstem symptoms (13%), or with mixed symptoms (11%). Distribution of clinical phenotypes were classic SPS (74%), SPS-plus (12%), stiff limb syndrome (6%), pure cerebellar (5%), and PERM (3%). The most commonly identified autoantibody was anti-GAD65, and others of interest were anti-amphiphysin, -glycine receptor, and -neuronal nuclear antibodies. Rarely, a paraneoplastic etiology was identified, associated with small cell lung cancer (2), breast cancer (2), and thymoma (1). EMG/NCS was abnormal in 60%. The majority of patients tried both symptomatic and immune therapies, most common being benzodiazepines and either IVIG or rituximab, respectively. The average modified Rankin Score at last visit was 2.5.