Changes in directly recorded cochlear nerve compound action potentials during acoustic tumor surgery

Area of Science:

• Neurosurgery
• Audiology
• Otolaryngology

Background:

• Hearing preservation after acoustic neuroma removal can be challenging due to damage to auditory structures.
• The exact causes of auditory impairment during these surgeries are not always clear.

Purpose of the Study:

• To investigate the correlation between surgical maneuvers and auditory function during acoustic neuroma removal.
• To assess the utility of intraoperative monitoring of auditory evoked potentials for predicting hearing outcomes.

Main Methods:

• Simultaneous recording of brainstem auditory evoked potentials and direct cochlear nerve action potentials (CNAPs) in 14 patients with small acoustic neuromas.
• Analysis of CNAP latency, temporal, and morphologic patterns to detect intraoperative auditory damage.

Main Results:

• The latency of the N(1) component of CNAPs was highly sensitive in detecting intraoperative auditory damage.
• CNAP patterns effectively identified critical surgical steps associated with hearing risk, including coagulation near the cochlear nerve, internal auditory canal drilling, and intrameatal tumor removal.
• CNAP latency served as a reliable predictor of postoperative hearing preservation.

Conclusions:

• Intraoperative monitoring of CNAPs is a valuable tool for assessing auditory function during acoustic neuroma surgery.
• Specific surgical maneuvers pose the highest risk to hearing, and CNAP analysis can guide efforts to preserve hearing.
• CNAP monitoring enhances the understanding of auditory damage mechanisms and improves prediction of surgical outcomes.