This study will attempt to determine the effectiveness of intravenous immunoglobulin (IVIg) for the treatment of Stiff-mann Syndrome. Patients participating in this study will be divided into two groups. Group one will receive 2 injections of IVIg once a month for three months. Group two will receive 2 injections of placebo "inactive sterile water" once a month for three months. Following the three months of treatment, group one will begin taking the placebo and group two will begin taking IVIg for an additional 3 months. The drug will be considered effective if patients receiving it experience a significant improvement in muscle function, mobility, and stiffness.