Differentiation between uniform and non-uniform motor nerve conduction slowing.
OBJECTIVE
Demyelination may cause a uniform reduction of the conduction velocity of all fibres of a peripheral nerve segment, or may affect only certain nerve fibres in a non-uniform way while sparing others. This study was done to improve the detection of non-uniform conduction slowing by using the high-frequency attenuation (HFA) method.


METHODS
Nerve conduction data from patients with early inflammatory demyelinating neuropathy (non-uniform demyelination, n=20), hereditary neuropathy (uniform demyelination, n=9), motor neuron disease (axon loss, n=20), and from healthy control subjects (n=20) were analysed.


RESULTS
HFA, compound muscle action potential (CMAP) amplitude decay, and F-wave chronodispersion correlated significantly. Among these variables both HFA and amplitude decay most sensitively identified non-uniform demyelination (35%). In the patients with uniform demyelination, the most frequent finding was a reduced nerve conduction velocity (NCV) (100%). The most specific marker of non-uniform demyelination was HFA. For uniform demyelination it was NCV.


CONCLUSIONS
The pattern of correlations between the variables studied confirms that NCV and F-min are indicators of uniform conduction slowing. HFA, amplitude decay, and F-wave chronodispersion indicate non-uniform conduction slowing, for which HFA is both sensitive and specific.


CONCLUSIONS
The HFA method improves both the diagnostic sensitivity and specificity of nerve conduction studies in patients with non-uniform demyelination.
Neurologische Klinik und Poliklinik, Universität Regensburg, Universitätsstrasse 84, 93053 Regensburg, Germany.
Volker
V
Busch
Wilhelm J
WJ
Schulte-Mattler
D000200:Action Potentials / Q000502:physiology; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D003711:Demyelinating Diseases / Q000175:diagnosis* / Q000503:physiopathology; D003937:Diagnosis, Differential; D004558:Electric Stimulation; D004576:Electromyography; D019054:Evoked Potentials, Motor; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D016472:Motor Neuron Disease / Q000175:diagnosis* / Q000503:physiopathology; D009046:Motor Neurons / Q000502:physiology*; D009431:Neural Conduction / Q000502:physiology*