Auditory Brainstem Evoked Potential Responses in Focal Brain Lesions

ABSTRACT

Brainstem auditory response abnormalities directly reflect disturbance of neural function rather than the underlying anatomic cause of that disturbance. The test has advantage in detecting lesions that alter electrophysiology but do not produce detectable alterations of radiodensity, displace surrounding structures or change vascular supply and permeability. A sequence of seven low-amplitude potentials that occur in the initial 10 msec following click signals can be recorded from scalp electrodes in 44 patient with focal brain lesions using computer averaging techniques. The potentials, termed auditory brainstem responses, are thought to be the far-field reflection of electrical events originating in the auditory pathway during its course through the brainstem. We have studied auditory brainstem evoked potential responses in a variety of focal brain lesions and found them to be of assistance in evaluating the localization of pontomedullary, pons, midbrain, thalamus, subcortical and functional recovery. 1) Distortion of early components (type I) was occured in the brainstem lesions. 2) Distortion of late components (type II) was developed in the diencephalon or subcortical lesions. 3) Distortion of all components (type III) was developed in the brainstem and diffuse brain contusions. 4) Serial recordings provided information about the evolution of brain stem lesions and good functional recovery marker.