Intraoperative Electrical Stapedius Reflex Testing to Monitor Cochlear Nerve Integrity during Simultaneous Vestibular...

Area of Science:

• Neurosurgery
• Otolaryngology
• Auditory Neuroscience

Background:

• Vestibular schwannoma (VS) resection often necessitates cochlear nerve monitoring.
• Simultaneous VS resection and cochlear implantation (CI) presents unique monitoring challenges.

Purpose of the Study:

• To compare intraoperative electrically evoked auditory brainstem response (eABR) and electrically evoked stapedial reflex testing (eSRT) for cochlear nerve integrity monitoring.
• To assess the utility of these methods during simultaneous translabyrinthine resection of VS and CI.

Main Methods:

• Historical cohort study involving 12 cases of simultaneous VS resection and CI placement.
• A CI was placed pre-resection to enable intraoperative monitoring via CI-delivered electrical stimuli.
• Outcomes of eABR and eSRT were correlated with postoperative CI performance, specifically open-set speech perception.

Main Results:

• Electrically evoked auditory brainstem response (eABR) was present in 10 of 12 cases, with 6 achieving open-set speech perception.
• Electrically evoked stapedial reflex testing (eSRT) showed a strong correlation with outcomes: 7 of 8 positive eSRT cases achieved open-set speech perception, while none of the 4 negative eSRT cases did.
• eSRT demonstrated higher reliability in predicting postoperative hearing outcomes compared to eABR.

Conclusions:

• Intraoperative eSRT using an unmodified CI is a promising method for monitoring cochlear nerve integrity during simultaneous VS resection and CI.
• eSRT response at the end of tumor resection strongly correlates with the cochlear implant's capacity for open-set speech.
• eABR, while useful, was less reliable in predicting postoperative hearing outcomes in this study.