Base neuronal dos potenciais evocados auditivos

Abstract

The auditory brainstem response (ABR) is an evoked potential extracted from electrical activity in the brainstem, in response of acoustic stimulus, and recorded via electrodes placed on the scalp, which enables a neurophysiological analysis of the auditory pathway, and consists in a useful instrument to detect various types of disorders affecting the auditory pathways of the central nervous system. Auditory processing refers to a set of processes which involves analysis and interpretation of sound stimuli and can be defined as the number of mental operations an individual performs to handle information through the sense of hearing. The auditory system has a number of pathways connecting the mechanoreceptors located in the cochlea to neurons distributed in the various centers in the medulla oblongata, the pons, the midbrain, the thalamus, and the cerebral cortex. The waves formed in the auditory evoked potentials of the brainstem are generated by sequential and synchronous activation of nerve fibers along these auditory pathways. This work aims to show how the auditory system processes sound stimuli and how the electrical activity generated by the eighth cranial nerve, neuronal centers and tract in the brainstem, in response of these stimuli, is recorded, allowing a neurophysiological analysis of the auditory pathways . It is divided in three parts. Part I provides an introduction of the cytology of neurons, the membrane potential, the action potential, the synaptic potentials, the electrical basis of EEG and hearing. Part II describes the evoked potential of the brainstem, acquisition techniques, the types of stimuli, the recorded parameters and variables that can affect the responses. Part III describes the clinical applications of the ABR in the neurological evaluation and some disorders associated with the dysfunction of the auditory pathways in the brainstem.