When the brain processes or transmits auditory stimuli, it produces sensory responses that are termed Brainstem Auditory Evoked Potential (BAEP). Like the evoked responses tracked by the SSEP modality, these impulses are minute and commonly lost in background electrical activity. NMSA gathers scores of signals from sterile subdermal needle electrodes in the scalp, and averages them while carefully filtering out background electrical activity. Response patterns detected by the BAER modality help pinpoint auditory pathway issues that may occur between the ear and midbrain.
Readings in this modality are tracked continuously during the surgery. Some data indicate that BAER may reduce hearing loss during selected procedures. This modality may be contraindicated in
patients with extensive hearing impairment or in ORs with significant noise levels.A modality with a nearly three-decade track record, BAER IONM effectively monitors the integrity of the auditory and visual systems despite temperature differentials and anesthesia use. Often employed as an adjunct to other modalities, it is indicated for surgical procedures such as posterior fossa craniotomies, basilar artery aneurysms, lateral cerebral cortex evaluation and arteriovenous malformation correction.