Focal nerve enlargement is not the cause for increased distal motor latency in ALS: Sonographic evaluation

Clin Neurophysiol. 2015 Aug;126(8):1632-7. doi: 10.1016/j.clinph.2014.10.152. Epub 2014 Nov 1.

Abstract

Objective: To elucidate the mechanism of focal conduction slowing in the median nerve in ALS.

Methods: The patients with ALS and CTS and normal control subjects were tested with sonography of the median and ulnar nerves. The cross-sectional areas (CSAs) and the wrist-forearm CSA ratios were compared with the parameters of nerve conduction study.

Results: The median motor distal latency was frequently prolonged in ALS and CTS. CSA and the wrist-forearm ratio of the median nerve were smaller in ALS than in CTS. The ulnar nerve sonography was similar in all the groups.

Conclusions: Selective conduction slowing of the median nerve at the wrist in ALS is unlikely due to secondary compressive neuropathy, as seen in carpal tunnel syndrome.

Significance: Unique vulnerability of the median nerve in ALS may explain the selective conduction slowing.

Keywords: ALS; Carpal tunnel syndrome; Distal latency; Median nerve; Sonography.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Action Potentials / physiology*
  • Aged
  • Aged, 80 and over
  • Amyotrophic Lateral Sclerosis / diagnostic imaging
  • Amyotrophic Lateral Sclerosis / physiopathology*
  • Carpal Tunnel Syndrome / diagnostic imaging
  • Carpal Tunnel Syndrome / physiopathology
  • Electromyography
  • Female
  • Humans
  • Male
  • Median Nerve / diagnostic imaging
  • Median Nerve / physiopathology*
  • Middle Aged
  • Neural Conduction / physiology*
  • Ultrasonography