The depression of the auditory nerve-brain-stem evoked response in hypoxaemia - mechanism and site of effect

H. Sohmer*, S. Freeman, M. Gafni, K. Goitein

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

90 Scopus citations

Abstract

During severe hypoxaemia in the cat the ABR was depressed in 2 different patterns: if mean arterial blood pressure (MAP) was maintained then all other evoked potentials (EPs - somatosensory and visual) remained. If MAP was not maintained, all of these EPs were depressed. This study sought to document these different patterns of ABR depression and to ascertain their mechanisms. When MAP fell, the ABR loss began with the later waves and progressed to the earlier waves. These are signs of a central brain lesion. The hypoxaemia, detrimental to normal function of the cardiovascular system, leads to depression of MAP, to a fall in cerebral perfusion pressure and blood flow, to cerebral ischaemia and ABR loss. On the other hand, when MAP was maintained, severe hypoxaemia was accompanied by a depression of all of the ABR waves at the same time. The cochlear microphonic potential was also simultaneously depressed. These are signs of peripheral, cochlear effect similar to the demonstrated depression of the positive endocochlear resting potential of the scala media and of the cochlear microphonic potential during hypoxaemia. This leads to interference with cochlear transduction mechanism so that all of the auditory evoked potentials, including the ABR, are simultaneously depressed. These results lead to the suggestion that the ABR abnormalities seen in patients who suffered a hypoxic (anoxic) insult or an ischaemic episode (prolonged interpeak latencies, loss of later waves and finally all waves absent or only the first wave remaining) is always due to ischaemia even when the initial insult was hypoxic.

Original languageEnglish
Pages (from-to)334-338
Number of pages5
JournalElectroencephalography and Clinical Neurophysiology
Volume64
Issue number4
DOIs
StatePublished - Oct 1986

Keywords

  • auditory brain-stem response
  • cochlear microphonic potential
  • endocochlear potential
  • hypoxaemia
  • ischaemia

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