Quantitative Assessment of Response to Long‐Term Treatment with Intravenous Immunoglobulin in Patients with Stiff Person Syndrome

BACKGROUND: Stiff person syndrome (SPS) is an autoimmune condition involving antibodies against several components of the inhibitory synapse in the spinal cord, with glutamic acid decarboxylase antibodies being the predominant immune marker. SPS affects approximately 1 patient per million population per year. The effect of intravenous immunoglobulin (IVIG) has been established, but studies on the long‐term efficacy of regular IVIG are limited. OBJECTIVES: To review clinical details and long‐term treatment response using a patient‐reported questionnaire in SPS and related syndromes. METHODS: Patients were identified from a tertiary neuroimmunology clinic based on classical clinical symptoms, autoimmune profiles, and neurophysiological changes (Dalakas criteria). They were followed up after treatment to assess the response to IVIG. RESULTS: A total of 23 patients fulfilled the selection criteria. Patients' demographic profiles and clinical presentations were akin to that reported in literature. There was significant improvement in the functional ability (assessed by the modified Rankin scale [mRS]) and quality of life (QoL) following treatment with IVIG within 4 to 10 weeks (pre‐mRS vs. post‐mRS, P < 0.0001; pre‐QoL vs. post‐QoL, P = 0.0003) and sustained after 5 years of treatment (pre‐mRS vs. present mRS, P = 0.0003; pre‐QoL vs. present QoL, P = 0.0002). CONCLUSIONS: This article describes one of the largest single‐center experiences of 23 patients with SPS and related syndromes and is the first to establish the long‐term efficacy of regular IVIG using a patient‐reported scoring system (Birmingham Response to Immunomodulatory Therapy [BRIT]). Consistent improvement in QoL and functional scores were seen over nearly 5 years after regular use of IVIG. It is recommended to use BRIT scores to assess the initial response as well as to monitor continued improvement to immunomodulation in SPS.