Surgery ·
Handheld CNAP Mapping Identifies Cochlear Nerve During Vestibular Schwannoma Surgery
A retrospective, single-center cohort of 193 patients evaluated handheld cochlear nerve action potential (CNAP) mapping during vestibular schwannoma surgery. CNAP mapping identified the nerve more often than brainstem auditory evoked potential (BAEP) elicitation, and favorable CNAP responses were strongly associated with postoperative hearing preservation.
- CNAP mapping identified the nerve in 83.4% of cases.
- BAEP elicitation identified the nerve in 46.1%.
- Favorable CNAP responses were associated with hearing preservation.
- Retrospective, single-center results do not prove improved outcomes.
In this retrospective single-center cohort, 193 patients with histologically confirmed vestibular schwannoma underwent intraoperative auditory mapping from September 2021 to November 2024. Investigators used a bipolar handheld probe to record near-field CNAP responses along the presumed cochlear nerve course and compared results with BAEP monitoring. The primary endpoint was functional hearing preservation, defined as American Academy of Otolaryngology–Head and Neck Surgery class A–C.
CNAP mapping identified the cochlear nerve in 83.4% of cases, compared with 46.1% for intraoperative BAEP elicitation (p < 0.001). Hearing was preserved in 91.4% of patients with favorable CNAP responses, versus 8.1% without them (p < 0.001); the adjusted odds ratio was 37.0 (95% CI 9.28–217.8). A combined CNAP-plus-BAEP model had an area under the ROC curve of 0.91.
The findings suggest CNAP mapping may provide complementary real-time functional information when BAEP waveforms deteriorate. However, this was a retrospective, single-center study, and the authors note that hearing outcomes also depend on structural nerve integrity, particularly with large tumors. The results do not establish that using the technique improves outcomes.
In practice
For teams performing vestibular schwannoma surgery, handheld CNAP mapping may help localize the cochlear nerve and provide functional information complementary to BAEP monitoring, including when BAEP responses are difficult to elicit. In this retrospective, single-center cohort of 193 patients, favorable CNAP responses were strongly associated with postoperative hearing preservation, but the study does not show that adopting the technique improves hearing outcomes. Structural nerve integrity remained important, particularly in large tumors, so these findings alone do not establish a practice-changing monitoring strategy.
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Journal of Neurosurgery: Handheld cochlear nerve action potential mapping for real-time functional navigation in vestibular schwannoma surgery ↗This is an automated AI-condensed summary that has not yet been reviewed by an editor. Always consult the full item at the original source.