P228 Reversible axonal conduction blocks and sonographic distal median-nerve enlargement in a young patient with acute motor axonal neuropathy

Abstract

Objectives To present a patient with acute motor axonal neuropathy (AMAN) of benign course. AMAN is a subtype of Guillain-Barre syndrome (GBS), characterized by reduced compound muscle action potentials (CMAP) and the absence of demyelinating findings. Patient Following a diarrhea, the 19-year-old male patient presented with distally pronounced moderate quadriparesis without sensory or autonomic symptoms. Cerebrospinal fluid was normal. The first electrophysiological evaluationshowed generalized very low/absent distal CMAPs without demyelinating signs. Electromyography (EMG) showed no denervation. Nerve ultrasound showed a distally enlarged median nerve with normal parameters of other nerves. Recovery started spontaneously and was accelerated by treatment with immunoglobulins. Follow-up electrophysiological study was performed 10 weeks after symptom-onset, showing significant but partial recovery of CMAP amplitudes without denervation in EMG. Discussion AMAN encountered in North-America and Europe is a rare and severe condition with poor outcome, due to widespread axonal degeneration. However, in the Far-East AMAN is a common and benign GBS type, with complete recovery in most patients. In this type, axonal dysfunction leads to reversible axonal conduction failure, rather than axonal degeneration, which may be confused with conduction blocks of demyelinating origin associated with acute inflammatory demyelinating polyneuropathy (AIDP). Conclusion The benign form of AMAN with reversible motor axonal conduction failure may occasionally be encountered in Europe as well, and may cause confusion in the electrophysiological diagnosis of GBS. Whereas AIDP patients generally have proximally enlarged nerves in the ultrasound, our AMAN-patient showed a distally enlarged median nerve, possibly related to the distal conduction failure.