Elsevier

Hearing Research

Volume 91, Issues 1–2, November 1995, Pages 19-32
Hearing Research

Research paper
Quantitative evaluation of myelinated nerve fibres and hair cells in cochleae of humans with age-related high-tone hearing loss

https://doi.org/10.1016/0378-5955(95)00158-1Get rights and content

Abstract

In this study 9 human temporal bones from 8 individuals were fixed with Karnovsky solution by perilymphatic perfusion within 1–3 h after death and examined using the ‘block-surface method’ (Spoendlin and Brun, 1974; Spoendlin and Schrott, 1987) and the ‘micro-dissection method’ (Johnsson and Hawkins, 1967). The audiogram of 7 individuals showed high-tone hearing loss, typical for sensory-neural presbycusis. The inner (IHC) and outer hair cells (OHC) and the myelinated nerve fibers in the osseous spiral lamina were counted to correlate audiometric curves with hair-cell and nerve-fiber densities. The ‘block-surface’ method allows accurate hair-cell and myelinated nerve-fiber enumeration with maximal preservation of cochlear structures.

The most significant change in the cochlea was not the expected loss of hair cells but an evident loss of nerve fibres in the spiral lamina along the entire length of the cochlea. This loss of nerve fibres was found to be age-related. Reductions up to 30–40% in comparison to normal-hearing middle-aged persons were found in cochleae from persons older than 60 years. In 2 cases only 13% of the fibres remained in some regions of the cochlea. The hair-cell counts showed a reduction of approximately 80% of the OHCs, mainly in the apical parts of the cochlea, and only little differences in the number of IHCs as compared with a group of normal-hearing middle-aged persons.

We conclude that neither loss of hair cells nor primary degeneration of nerve fibres alone can fully explain the high-tone loss. Probably injuries of hair cells or neuronal elements at the cellular level can cause threshold elevation.

References (36)

  • H. Spoendlin et al.

    Analysis of the human auditory nerve

    Hear. Res.

    (1989)
  • O. Ahrentschild

    Das alternde Ohr: Funktionelle Aspekte

    HNO

    (1971)
  • B.A. Bohne et al.

    Morphological correlates of aging in the chinchilla cochlea

    Hear. Res.

    (1990)
  • P. Bumm

    Überschwellige Befunde des Ton- und Sprachgehörs bei Presbyacusis

    Arch. Otorhinolaryngol.

    (1980)
  • G. Bredberg

    Cellular pattern and nerve supply in the human organ of Corti

    Acta Otolaryngol. (Stockh.)

    (1968)
  • D.E. Crowley et al.

    An animal model for presbycusis

    Laryngoscope

    (1971)
  • S.V. Dayal et al.

    Comparative study of age-related cochlear hair cell loss

    Ann. Otol. Rhinol. Laryngol.

    (1986)
  • V.S. Dayal et al.

    Patterns of pure tone loss in presbycusis

    Acta Otolaryngol. (Stockh.)

    (1971)
  • M. Gleeson et al.

    A comparative study of the effect of age on the human cochlear and vestibular neuroepithelia

    Acta Otolaryngol. (Stockh.)

    (1987)
  • A. Glorig et al.

    Age, noise and hearing loss

    Ann. Otol. Rhinol. Laryngol.

    (1961)
  • G.A. Gates et al.

    Incidence of hearing decline in the elderly

    Acta Otolaryngol. (Stockh.)

    (1991)
  • S.R. Guild

    Correlations of histologic observations and the acuity of hearing

    Acta Otolaryngol. (Stockh.)

    (1932)
  • L. Ha-Sheng et al.

    Age-related loss of auditory sensitivity in two mouse genotypes

    Acta Otolaryngol. (Stockh.)

    (1991)
  • R. Hinchcliffe

    The anatomical locus of Presbycusis

    J. Speech Hear. Disorders

    (1962)
  • L.G. Johnsson

    Degenerative Veränderungen im alternden Innenohr mit besonderer Berücksichtigung der vasculären Veränderungen, in Flächenpräparaten der menschlichen Cochlea dargestellt

    Arch. Klin. Exp. Ohr- Nasen- u. Kehlk. Heilkunde

    (1971)
  • L.G. Johnsson et al.

    A direct approach to cochlear anatomy and pathology in man

    Arch. Otolaryngol.

    (1967)
  • L.G. Johnsson et al.

    Observations on the pattern of sensorineural degeneration in the human cochlea

    Acta Otolaryngol. (Stockh.)

    (1990)
  • M.E. Keithley et al.

    Hair cell counts in age graded series of rat cochleas

    Hear. Res.

    (1982)
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