Randomized Placebo Controlled Trial of IVIg in Glycine Receptor Antibody Positive Stiff-person Syndrome

Inclusion Criteria * Patient must be 18 years of age or older * Must have symptoms of SPS for less than 3 years * If taking corticosteroids, the patients must be on a stabile dose for 30 days prior to enrolment * Patients will have a diagnosis of SPS spectrum disorder based on both of clinical and serological status Exclusion Criteria * Patients on immune suppressants initiated/dose increased in the prior 6 months * History of thrombotic episodes within the 2 years prior to enrollment * Known allergic or other severe reactions to blood products including intolerability to previous IVIG * Previous adequate trial of IVIG as determined by the Principal Investigator * IgA deficiency * Reproductive status: * Women who are pregnant, breastfeeding * Women and men of childbearing potential who are unwilling or unable to use an acceptable method of birth control to avoid pregnancy for the entire study period, as evaluated by the investigator. * Any surgical procedure within 4 weeks prior to baseline. * Evidence of serious uncontrolled concomitant diseases that may preclude patient participation; Other nervous system disease, cardiovascular disease, hematologic/hematopoiesis disease, respiratory disease, muscular disease, endocrine disease, renal/urologic disease, digestive system disease, congenital or acquired severe immunodeficiency * Known active infection within 4 weeks prior to baseline. * Evidence of chronic active hepatitis B or C. * Active ischemic heart disease in the past year prior to baseline. * Patients should not have severe renal or hepatic disease * Severe hypertension