P1-37. Distal compound muscle action potential dispersion would commonly occur in patients with anti-MAG/SGPG antibody associated neuropathy

Abstract

The prolonged distal compound muscle action potential (CMAP) duration (i.e. distal temporal dispersion) has been recently validated as a measure of distal demyelination in chronic inflammatory demyelinating polyneuropathy (CIDP) patients. In previous reports, distal temporal dispersion was rare in patients with anti-MAG/SGPG antibody associated neuropathy. Here, to test this notion, we studied distal CMAP duration in our patients. Subjects were 5 patients with anti-MAG and/or anti-SGPG antibody associated neuropathy. We performed conventional motor conduction studies in unilateral median, ulnar and tibial nerves. The cut-off point of distal temporal dispersion was set at 9ms based on a previous report. Distal CMAP duration was prolonged in 4 of 5 patients. Among 13 responses, 50% (median), 60% (ulnar) and 75% (tibial) presented distal temporal dispersion. There were negative correlation between distal CMAP duration and conduction velocity (R[2] = 0.63, p = 0.0012), and positive correlation between distal CMAP duration and distal latency (R[2] = 0.75, p = 0.0001). Our findings suggest that distal temporal dispersion is not rare in patients with anti-MAG/SGPG antibody associated neuropathy, which is in contrast to previous reports.