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  • Importance of Low-Amplitude Positive Facial Nerve Stimulation Following Cerebellopontine Angle Tumor Surgery

    Final Number:

    Bharat Guthikonda MD; Shashikant Patil MD; Shihao Zhang MD; Osama Ahmed MD; Anil Nanda MD FACS

    Study Design:
    Clinical Trial

    Subject Category:

    Meeting: Congress of Neurological Surgeons 2011 Annual Meeting

    Introduction: Preservation of facial nerve function is crucial to a successful cerebellopontine angle tumor resection. We sought to correlate short and long-term facial nerve function with respect to the minimum amplitude of stimulation required to obtain facial nerve identification at the conclusion of the tumor resection.

    Methods: We performed a review of a prospectively collected database of patients who underwent CP angle tumor surgery from 9/2007 to 9/2010. The minimum amplitude necessary to achieve facial nerve stimulation was noted at the end of each tumor resection. Facial nerve function outcomes (HB grading scale) were noted at 3 different times: post operative day 1, 1 month post-op, and 6 months post-op.

    Results: 20 CP angle tumor resections were performed in our study time span (15 acoustic neuroma, 4 meningioma, 1 ganglioglioma). Positive facial nerve stimulation was achieved in all cases at the conclusion of tumor resection. The minimum threshold to achieve this final positive stimulation ranged from 0.1 to 1 milliampere (mean = 0.34 mamp). Immediated post-operative function varied from HB 1 to HB 4 (mean= 2.3). 1 month post operative facial function varied from HB 1 to HB 3 (mean = 1.6). 6 month post operative facial function varied from HB 1 to HB 2 (mean = 1.05).

    Conclusions: Our study showed that the final facial nerve stimulation with low amplitude led to good long-term facial nerve outcomes. We also noted that despite some suboptimal immediate post operative facial nerve function, excellent long-term facial nerve function was seen in all patients. Our data stresses the importance of maintaining electrical as well as anatomic integrity of the facial nerve; we advocate doing this at all costs even if a thin layer of tumor is left adherent to the facial nerve.

    Patient Care: Will provide further evidence to support maintaining low amplitude facial nerve stimulation at the end of CP angle surgery, even if a small amount of residual tumor is left.

    Learning Objectives: By the conclusion of this session, participants will be able to 1) Describe facial nerve stimulation 2) Emphasize its importance during CP angle tumor resection 3) See results that advocate maintaining facial nerve integrity even if a small residual tumor is left


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