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Neuro-axonal recruitment: A result of selective compression

Published online by Cambridge University Press:  29 June 2007

Ernst Lehnhardt
Ernst Lehnhardt*
Affiliation:
Hannover, W. Germany
*
Prof. Dr. E. Lehnhardt: Director of ENT-DepartmentMedizinische Hochschule Hannover, P.O.B. 61180, D-3000 Hannover 61, W. Germany.
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Abstract

Many acoustic neurinomas and CPA tumours present an audiometric picture of positive-recruitment hearing impairment although often the CMs are not significantly impaired (according to ECochG) and because, even in the case of a small acoustic neuroma, the interpeak latency between wave I and V (ERA) is increased in the majority of cases. Recruitment cannot be explained, in these cases, as an expression of an accompanying vascular inner ear lesion. Therefore, we attempt to interpret the differential audiometric picture to the various patterns of damage of the auditory nerve. The finding of tone decay is seen as an expression of myelin damage corresponding to the hearing loss in multiple sclerosis.

The absence of any degree of tone decay excludes an isolated damage of the myelin sheaths; hearing loss then results from a disturbance also of the associated axons. At such a stage, where there is a functional loss to part of the neural fibres but with intact myelinated residual fibres, the result could be the phenomenon of recruitment for suprathreshold stimulation. This theory of selective compression is compared to an isolated efferent lesion theory as the cause for recruitment in AN and CPA tumours.

Type
Main Articles
Information
The Journal of Laryngology & Otology , Volume 104 , Issue 3 , March 1990 , pp. 185 - 190
Copyright
Copyright © JLO (1984) Limited 1990

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