Which factors contribute to the clinical usefulness of brainstem auditory evoked potentials (BAEPs)?

Updated: Oct 25, 2019
  • Author: Andrew B Evans, MD; Chief Editor: Selim R Benbadis, MD  more...
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Factors influencing peak latencies of BAEPs include the following:

  • Patient age

  • Patient sex

  • Auditory acuity stimulus repetition rate

  • Stimulus intensity

  • Signal polarity

Rarefaction (ie, movement of the earphone diaphragm away from the eardrum) produces an increase in wave I amplitude. In severe hearing loss, all waveforms may be delayed, wave I may be absent with waves II through V delayed, or all waveforms may be absent. Note that in patients with hearing loss, BAEPs still can be obtained to assess central conduction time by increasing stimulation intensity.

Kern et al studied the effects of insulin-induced hypoglycemia on the auditory brainstem response (ABR) in humans. [25] ABRs were examined in 30 healthy men during euglycemia and after 20 minutes and 50 minutes of steady-state hypoglycemia of 2.6 mmol/L induced with insulin. Hypoglycemia increased interpeak latencies III-V and I-V, whereas changes in the latency of wave I were not significant.

BAEPs are very resistant to alteration by anything other than structural pathology in the brainstem auditory tracts. They are not significantly affected by barbiturate doses sufficient to render the electroencephalogram (EEG) “flat” (ie, isoelectric) or by general anesthesia (though Garcia-Larrea et al reported BAEP loss with combined lidocaine and thiopental infusion [26] ).

Disorders of the peripheral vestibular system do not affect BAEP. Thus, 21 patients who had labyrinthine diseases (ie, Ménière disease, labyrinthitis, vestibular neuronitis) had no BAEP interwave latency abnormalities in terms of the limits employed for clinical neurologic purposes.

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