A review of objective methods of evaluating auditory neural pathways.

OBJECTIVES: Review physiological methods of evaluating function of the auditory neural pathways in infants, children, and adults. Present two case studies to demonstrate the usefulness of physiological measures in assessing abnormalities of the auditory neural pathways. STUDY
DESIGN: Review of applications of physiological measures of auditory neural function.
METHODS: Review otoacoustic emissions, auditory evoked potentials, and efferent reflexes, and discuss their use in identifying disorders of the auditory neural pathways from the cochlea to the cortex.
RESULTS: Auditory disorders occur from peripheral to central areas of the neural system. Patients with disorders of the peripheral nerve and/or the input from the cochlear inner hair cells, such as the patients presently described as having auditory neuropathy, demonstrate abnormal efferent reflexes, including middle ear muscle reflexes and efferent suppression of otoacoustic emissions, as well as grossly abnormal brainstem evoked potentials. In contrast, patients with more central disorders can be differentiated by normal results on tests of the neural periphery and abnormal findings on cortical evoked potentials and other measures of central function.
CONCLUSIONS: Physiological measures are sensitive, objective, and less variable in assessing neural disorders than traditional behavioral measures such as pure-tone or speech audiometry.