Abstract
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 ...
Abstract
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. Significance: The HFA method improves both the diagnostic sensitivity and specificity of nerve conduction studies in patients with non-uniform demyelination. (C) 2010 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.
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