Presynaptic neuromuscular transmission defect in the Miller Fisher syndrome

The Miller Fisher syndrome (MFS) is associated with elevated anti-GQ1b antibodies.1 The pathophysiology of MFS involves immunologically mediated central and peripheral processes.2 In vitro studies of MFS have demonstrated anti-GQ1b-mediated presynaptic damage at the neuromuscular junction.3 This mechanism may be responsible for some of its clinical manifestations. Repetitive nerve stimulation (RNS) is a validated electrophysiologic technique for assessing neuromuscular transmission.4 In this study, we present serial RNS data on patients with MFS, in relation to their clinical course. Over a 3-year period, we prospectively evaluated six consecutive previously healthy patients presenting with MFS. The patients presented with the classic clinical triad (ataxia, areflexia, and ophthalmoplegia) of MFS, and none was weak. All patients had a complete neurologic examination as well as routine nerve conduction studies. Anti-Gq1b assays5 were performed during hospital admission. RNS of the ulnar nerve was performed with right abductor digiti minimi recording.4 RNS was performed at the following frequencies in random order: 3 Hz at rest, 3 Hz post exercise, 20 Hz, and 50 Hz. Exercise consisted of 20 seconds of maximal muscle activation. Each …