Intraoperative Monitoring of Auditory Function during Lateral Skull Base Surgery

Objective:We present a unique case of a patient with a jugular foramen tumor with serviceable hearing. This study discusses the audiometric results and intraoperative electrocochleographic (ECochG) findings recorded during tumor removal to illustrate the potential utility of this technique in skull base surgery.Patients:A 22-year-old female patient presented with a jugular foramen schwannoma and associated symptoms of right-sided otalgia, mild hearing loss, and blurry vision.Interventions:Intraoperative ECochG responses during an infratemporal fossa approach: click and tone burst (1, 2, 4kHz) stimuli were used and presented at 90dB nHL.Main Outcome Measures:Intraoperative ECochG testing using frequency-specific tone bursts and clicks before and after tumor resection.Results:The compound action potential magnitudes, cochlear microphonic, and summation potential were recorded pre- and post-tumor removal. For statistical analysis, a paired t test with significance set at p<0.05 was used. The compound action potential magnitudes increased at all test frequencies (p<0.01) while the summation potential and cochlear microphonic remained relatively stable (p>0.05). Audiometric testing demonstrated an improvement of the preoperative mild right-sided hearing loss after tumor resection (pure-tone average for 0.5, 1, 2, and 4kHz of 30dB HL preoperation and 7.5dB HL after tumor resection).Conclusions:Intraoperative ECochG may allow for real-time monitoring during complex skull base surgery.