Multimodal intraoperative monitoring of facial nerve function: combined use of blink reflex and corticobulbar motor evoked potentials.

OBJECTIVE

To compare the intraoperative blink reflex (BR) and facial corticobulbar motor evoked potentials (FCoMEPs) in skull base surgery, and to assess their respective and combined value in predicting postoperative facial nerve outcome.

METHODS

80 consecutive patients undergoing skull base surgery were monitored using ipsilateral FCoMEPs and bilateral BR recordings. BR was particularly assessed during stages in which FCoMEPs were limited by stimulus-induced movement. Facial nerve function was evaluated in the immediate postoperative period and at 6 months using the House-Brackmann (HB) scale. Cluster analysis was performed to identify patterns of intraoperative neurophysiological changes and their association with postoperative facial nerve outcome.

RESULTS

Monitorability was 98.6% for the BR and 100% for FCoMEPs. 28 patients developed postoperative facial palsy, severe (HB V-VI) in eight cases. Seven of these patients showed significant intraoperative changes in both BR and FCoMEPs, whereas one showed no changes and recovered within days. All patients with mild to moderate dysfunction (HB II-III) recovered during follow-up. No patient with preserved BR at the end of surgery developed long-term facial nerve paresis. A reduction greater than 50% in BR and FCoMEP amplitudes was associated with poor facial nerve outcome (HB IV-VI).

CONCLUSIONS

Preserved BR and FCoMEPs are associated with favorable postoperative facial nerve outcome, whereas intraoperative loss of both modalities predict moderate to severe and potentially permanent facial nerve dysfunction. Preservation of BR at the end of surgery reliably indicates intact or only transient facial nerve impairment.

SIGNIFICANCE: We describe novel features of BR that underscore its importance as a complement to FCoMEPs in skull base surgery.