Abstract
Objective: To evaluate a continuous facial nerve (FN) stimulating burr (the StimBurGard) during otologic/neurotologic procedures in terms of safety and reliability when drilling in contact with the Fallopian canal (FC) of the mastoid segment of the FN.
Study Design: Prospective clinical trial.
Setting: Tertiary referral center.
Patients: Thirty-five patients operated through translabyrinthine (TL) approach for vestibular schwannoma removal were divided into 3 groups. Group 1 (5 patients): the stimulation current was set at 3 and then at 2 mA visualizing the localization of the burr when the first response at 100-mu V threshold was obtained in the mastoid cavity. Group 2 (15 patients): exposure of the FC in the mastoid segment during TL approach was stopped when the first response was obtained at 1-mA stimulation; FC thickness in the second genu and mastoid segment of the FC was evaluated on a postoperative computed tomographic (CT) scan, and FC dehiscence observed on CT scan was compared with surgical observation. Group 3 (15 patients), exposure of the FC was performed as routinely done during a TL approach and surgical observation of FC dehiscence; stimulation values in mA at the 100 mu V threshold and FC thickness on postoperative CT scan were evaluated. In all cases, the stimulation value at the cerebellopontine angle root of the FN with a 100-mu V response threshold was measured before tumor resection.
Results: Group 1: stimulation at 3 mA occurred in aditus ad antrum and at 2 mA near the FC. Group 2: mean thickness of 1.09 +/- 0.69 mm with 2 cases of radiologic dehiscence of the FN. Group 3: the stimulation threshold was 0.6 +/- 0.37 mA, and the thickness was 0.41 +/- 0.56 mm with 9 cases of uncovered FN (p = 0.0082). In all patients, FN at brainstem was stimulated at 0.03 mA before VS dissection.
Conclusion: Continuous FN stimulating burr by means of the StimBurGard system is a safe and effective tool for FN stimulation and identification. The integrity of FC is preserved in most cases when the stimulation intensity is 1 mA.