The relative diagnostic sensitivity of different F-wave parameters in various polyneuropathies.
We studied F-wave minimum latency, persistence, and chronodispersion in the median and ulnar nerves of 70 controls and 75 patients with various polyneuropathies. Prolonged minimum latency was the most frequent F-wave abnormality in all groups of patients with polyneuropathy. The finding of decreased persistence or absence of F-responses was comparable in sensitivity to prolonged minimum latency in Guillain-Barré syndrome (GBS) and chronic inflammatory demyelinating polyneuropathy (CIDP), whereas chronodispersion had a comparable sensitivity only in CIDP. Decreased persistence of obtained F-responses, and the absence of F-responses in nerves with low compound muscle action potential amplitudes, were nonspecific findings. F-wave studies often provide useful additional information in the evaluation of patients suspected of having a polyneuropathy. In patients with axonal polyneuropathies, we found that F-wave studies are significantly more sensitive than standard motor conduction studies in identifying physiological abnormalities of motor axons. Furthermore, in a patient with an acquired polyneuropathy, the finding of markedly prolonged minimum latency, or the absence of F-responses in nerves with normal CMAP amplitude, is highly specific for the presence of demyelination.
Fraser
J L
JL
Department of Neurology, School of Medicine, University of California, San Francisco 94143-0114.
Olney
R K
RK
D000328:Adult; D003711:Demyelinating Diseases / Q000175:diagnosis*; D003929:Diabetic Neuropathies / Q000175:diagnosis*; D004568:Electrodiagnosis; D006801:Humans; D008475:Median Nerve / Q000503:physiopathology; D008875:Middle Aged; D009431:Neural Conduction / Q000502:physiology; D011129:Polyradiculoneuropathy / Q000175:diagnosis*; D012016:Reference Values; D012680:Sensitivity and Specificity; D014459:Ulnar Nerve / Q000503:physiopathology