• Masahiko Wanibuchi, Yukinori Akiyama, Takeshi Mikami, Katsuya Komatsu, Toshiya Sugino, Kengo Suzuki, Aya Kanno, Shunya Ohtaki, Shouhei Noshiro, and Nobuhiro Mikuni.
• Department of Neurosurgery, Sapporo Medical University School of Medicine, Sapporo, Japan.
• Neurosurgery. 2016 Jun 1; 78 (6): 829-34.

BackgroundDamage to the motor division of the lower cranial nerves that run into the jugular foramen leads to hoarseness, dysphagia, and the risk of aspiration pneumonia; therefore, its functional preservation during surgical procedures is important. Intraoperative mapping and monitoring of the motor rootlets at the cerebellomedullary cistern using endotracheal tube electrodes is a safe and effective procedure to prevent its injury.ObjectiveTo study the location of the somatic and autonomic motor fibers of the lower cranial nerves related to vocal cord movement.MethodsTwenty-four patients with pathologies at the cerebellopontine lesion were studied. General anesthesia was maintained with fentanyl and propofol. A monopolar stimulator was used at amplitudes of 0.05 to 0.1 mA. Both acoustic and visual signals were displayed as vocalis muscle electromyographic activity using endotracheal tube surface electrodes.ResultsThe average number of rootlets was 7.4 (range, 5-10); 75% of patients had 7 or 8 rootlets. As many as 6 rootlets (2-4 in most cases) were responsive in each patient. In 23 of the 24 patients, the responding rootlets congregated on the caudal side. The maximum electromyographic response was predominantly in the most caudal or second most caudal rootlet in 79%.ConclusionThe majority of motor fibers of the lower cranial nerves run through the caudal part of the rootlets at the cerebellomedullary cistern, and the maximal electromyographic response was elicited at the most caudal or second most caudal rootlet.AbbreviationEMG, electromyographic.

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