Conduction slowing in diabetic distal polyneuropathy.
The pathophysiologic significance of motor conduction slowing observed in diabetic distal symmetrical polyneuropathy (DSP) remains controversial. We have used multiple linear regression analysis of compound muscle action potential (CMAP) amplitude vs. motor conduction velocity (CV) and distal latency (DL) in 57 patients with diabetic DSP and 34 patients with amyotrophic lateral sclerosis (ALS) to determine whether motor conduction slowing in diabetic DSP is due mainly to loss of large axons as in ALS or whether there is an additional demyelinative component. We found amplitude-dependent slowing of CV and DL in both diabetic DSP and ALS in the upper and lower extremities, consistent with a loss of large myelinated fibers. However, in diabetic DSP, there was also significant amplitude-independent slowing in intermediate but not distal nerve segments, supportive of an additional demyelinative component. CMAP amplitude vs. CV and DL regression analyses using ALS as a control group for relatively pure axon loss may provide pathophysiologic information about motor nerves in other neuropathic disorders.
Herrmann
David N
DN
Department of Neurology, University of Rochester, SMH 601 Elmwood Avenue, Box 673, Rochester, New York 14642, USA. David_Herrmann@urmc.rochester.edu
Ferguson
Michele L
ML
Logigian
Eric L
EL
D000200:Action Potentials; D000368:Aged; D001369:Axons / Q000502:physiology; D003711:Demyelinating Diseases / Q000175:diagnosis / Q000503:physiopathology; D003929:Diabetic Neuropathies / Q000175:diagnosis / Q000503:physiopathology*; D006801:Humans; D008875:Middle Aged; D009046:Motor Neurons / Q000502:physiology* / Q000648:ultrastructure; D009431:Neural Conduction; D011930:Reaction Time; D012044:Regression Analysis