Upper leg conduction time distinguishes demyelinating neuropathies.

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Muscle Nerve. 2011 Feb 11. doi: 10.1002/mus.21909. [Epub ahead of print]

Upper leg conduction time distinguishes demyelinating neuropathies.

Maccabee PJ, Eberle LP, Stein IA, Willer JA, Lipitz ME, Kula RW, Marx T, Muntean

EV, Amassian VE.

Department of Neurology, F. Furchgott Center for Neural and Behavioral

Science, SUNY Downstate Medical Center, 450 son Avenue, Brooklyn, New York

11203, USA; Department of Physiology, SUNY Downstate Medical Center, Brooklyn,

New York, USA.

Abstract

Background: The objective of this study was to determine whether differentiation

between demyelinating and axonal neuropathies could be enhanced by comparing

conduction time changes in defined segments of the total peripheral nerve

pathway.

Methods: Compound muscle action potentials (CMAPs) were elicited by cathodal

stimulation of the tibial nerve at the ankle and popliteal fossa, and by

paravertebral neuromagnetic stimulation at proximal and distal cauda equina

while recording from muscles of the foot, shin, and thigh. Segmental conduction

times were calculated in normal subjects; in patients with lumbosacral

radiculopathy, distal symmetric diabetic neuropathy, amyotrophic lateral

sclerosis, acute and chronic inflammatory demyelinating polyneuropathy; and in

patients with anti-myelin-associated glycoprotein, myelomatous, and

Charcot-Marie-Tooth type 1a polyneuropathies.

Results: Distal cauda equina latency and CMAP duration and segmental conduction

times in upper leg and cauda equina facilitated differentiation of demyelinating

from axonal neuropathies, even in the presence of a range of reduced amplitude

CMAPs.

Conclusions: Within the demyelinating neuropathy spectrum, it was further

possible to distinguish subtypes.