76.: Clinical improvement of complex regional pain syndrome accompanied by reduced peripheral nerve excitability following intravenous immunoglobulin

Abstract

Complex regional pain syndrome (CRPS) is a painful, debilitating and chronic condition. There is neither a disease-modifying treatment nor an objective test for the syndrome. A 32-year-old woman had features of CRPS in one arm following oropharyngeal herpes simplex virus-2 (HSV-2) infection. There was hyperaemia on bone scan during the delayed phase and a positive tilt table test. Autoantibodies were sought due to a known immune diathesis including novel neural antibodies using immunohistochemistry on rat tissue. Nerve excitability tests were performed acutely and at 6months. Immunoglobulin G (IgG) against spinal cord and dorsal root axons was found in this case but none of 10 controls with multiple sclerosis. The pattern was cytosolic and vesicular with sparing of the nodes of Ranvier. There was a demonstrable reduction in the excitability of peripheral median nerve motor and sensory axons with immunological treatments (intravenous [IV] IgG and immune suppressants). This case demonstrates an unusual aetiology of CRPS associated with autoimmunity and systemic autonomic dysfunction. Peripheral nerve excitability shows the effect of IVIg may be to reduce the excitability of neurons and possibly therefore central sensitization.