Transdural Stimulation for the Identification of a Dehiscent Geniculate Ganglion in Intradural Middle Cranial Fossa Surgery: A Proof-of-Principle Study.

PURPOSE: Facial nerve injury is a potential complication in intradural middle cranial fossa surgery, particularly because of dehiscence of the geniculate ganglion, exposing the nerve to thermal injury. Identifying the geniculate ganglion during surgical approaches is crucial for preserving facial nerve function. This study aimed to evaluate the feasibility and efficacy of transdural stimulation in identifying the geniculate ganglion during intradural approaches to improve the preservation of facial nerve function.

METHODS: We conducted a retrospective analysis on patients who underwent surgery for middle cranial fossa lesions using intraoperative neuromonitoring including facial motor evoked potentials and transdural direct nerve stimulation of the geniculate ganglion, from January 2016 to January 2024.

RESULTS: We identified eight consecutive patients with various pathologies of the middle cranial fossa who underwent surgery with direct nerve stimulation of the geniculate ganglion. Specific responses from facial muscles were registered in four out of eight patients, with stimulation intensity varying between 0.5 and 2 mA. None of the patients who underwent surgery with direct nerve stimulation experienced facial palsy. Notably, even when CT scans suggested bony covering of the geniculate ganglion, the facial nerve could still be stimulated.

CONCLUSIONS: This proof-of-principle study demonstrates that transdural stimulation is a promising technique for identifying the geniculate ganglion during intradural middle cranial fossa surgery. This approach has the potential to improve preservation of facial nerve function and reduce the risk of postoperative facial palsy.