BAEP (BRAINSTEM AUDITORY EVOKED POTENTIALS)

BAEP stands for “Brainstem Auditory Evoked Potentials” and evaluates the functions of the auditory nerves in all pathways from the inner ear to the auditory center in the brain. BAEP is used especially for the evaluation of problems such as hearing loss and tinnitus.

The stimulus is a “click” sound applied to each ear in turn via a headphone (or a probe placed in the external auditory canal, if necessary) at a frequency of approximately 10 Hz, with an intensity of 60-70 dB above the hearing threshold and with acoustic properties determined. The most commonly used “rereflection” click causes the eardrum to move outward. During this time, a “white noise” is given to the opposite side in order to mask the effect of the stimulus transmitted through the bone to the other ear. The potentials that constitute the BAEP are a series of waves that emerge as a result of the sequential activation of the brainstem auditory pathways following the auditory stimulus. Recording is done via electrodes placed on the right and left earlobes (or the skin on the mastoid process) and the vertex. Thus, the right ear-vertex and left ear-vertex connections are associated with one channel of the recording device, and two-channel recording is performed. The waves obtained are potentials with an amplitude of approximately 0.1-0.5 mV, i.e. 1/100 of the EEG activity. Therefore, more than 1500-2000 recordings should be averaged each time and, as in all UPs, the averaging should be repeated at least twice. The anatomical regions where the first five BAEP waves most commonly used in clinical localization are thought to originate are as follows:

Wave I: VIII nerve action potential

Wave II: Cochlear nucleus (and VIII nerve)

Wave III: Ipsilateral superior olivary nucleus

Wave IV: Lateral lemniscus nucleus or axons

Wave V: Inferior colliculus

In which cases is BAEP requested?