Author(s)
"1. Patricia Johnson, MD
Affiliation(s)
Abstract:
Objective: Preoperative temporal bone high-resolution computed tomography (HRCT) is used to assess middleear and mastoid anatomy. However, HRCT is an unreliable method of detecting facial canal dehiscence. Weaimed to determine if preoperative transcutaneous facial nerve (FN) stimulation at the stylomastoid foramencould predict middle ear facial canal dehiscence.Study design: Retrospective reviewSetting: Tertiary centerPatients: Records of adult patients who underwent otologic surgery at our institution from January 2015 toOctober 3, 2016 were reviewed. Those selected for inclusion had preoperative FN stimulation and HRCTavailable for review.Intervention: Using an FN stimulator placed on the skin over the stylomastoid foramen, the FN was stimulatedat amperages ranging from 0.01—30 milliamperes (mA). Thresholds to waveform formation and amplitudes ofcompound muscle action potential (CMAP) were recorded at all electrodes.Main outcome measures: Threshold to CMAP, average threshold to CMAP, threshold to maximum amplitudeof CMAP, and maximum amplitude of CMAP.Results: 34 patients met inclusion criteria. Of the 11 with intraoperatively confirmed dehiscences, 6 wereidentified by the attending surgeon on HRCT and 2 were identified on official radiology report. Mean lowestthreshold to CMAP (0.75mA vs 8.0mA), and mean maximum amplitude of CMAP (1835µV vs 1197µV) ofdehiscent versus non-dehiscent nerves were significantly different (p<0.05).Conclusions: Iatrogenic facial nerve injury is one of the most devastating potential complications of otologicsurgery. The use of facial nerve stimulation is a simple and cost-effective tool that can give the surgeonpresurgical confirmation of facial nerve anatomy.Define Professional Practice Gap & Educational Need: Lack of contemporary knowledgeLearning Objective: Understand that preoperative facial nerve stimulation can be used to provide informationabout facial nerve anatomy to supplement high resolution CT scan.Desired Result: They will use preoperative facial nerve stimulation to supplement knowledge of patient's facialnerve anatomy as described by high resolution CT scan.Indicate IRB or IACUC Approval: Exempt