Role of electrophysiology in guiding near-total resection for preservation of facial nerve function in the surgical treatment of large vestibular schwannomas

Abstract

OBJECTIVE In large vestibular schwannoma (VS) surgery, the facial nerve (FN) is at high risk of injury. Near-total resection has been advocated in the case of difficult facial nerve dissection, but the amount of residual tumor that should be left and when dissection should be stopped remain controversial factors. The objective of this study was to report FN outcome and radiological results in patients undergoing near-total VS resection guided by electromyographic supramaximal stimulation of the FN at the brainstem. METHODS This study was a retrospective analysis of a prospectively maintained database. Inclusion criteria were surgical treatment of a large VS during 2014, normal preoperative FN function, and an incomplete resection due to the strong adherence of the tumor to the FN and the loss of around 50% of the response of supramaximal stimulation of the proximal FN at 2 mA. Facial nerve function and the amount and evolution of the residual tumor were evaluated by clinical examination and by MRI at a mean of 5 days postoperatively and at 1 year postoperatively. RESULTS Twenty-five patients met the inclusion criteria and were included in the study. Good FN function (Grade I or II) was observed in 16 (64%) and 21 (84%) of the 25 patients at Day 8 and at 1 year postoperatively, respectively. At the 1-year follow-up evaluation (n = 23), 15 patients (65%) did not show growth of the residual tumor, 6 patients (26%) had regression of the residual tumor, and only 2 patients (9%) presented with tumor progression. CONCLUSIONS Near-total resection guided by electrophysiology represents a safe option in cases of difficult dissection of the facial nerve from the tumor. This seems to offer a good compromise between the goals of preserving facial nerve function and achieving maximum safe resection.

Early-Career Surgical Practice for Cerebellopontine Angle Tumors in the Era of Radiosurgery

“…In our institution, we follow the principle of attempting total resection under the constant surveillance of neurophysiological monitoring which means halting resection when alterations in facial nerve responses suggest potential severe damage. Looking at current experience and comparing to updated literature review, there seems to be a good agreement of results with modern large series [25][26][27][28][29][30][31][32][33] for both functional outcomes and resection strategies (►Table 8). These data are more relevant if one considers the fact that most of our patients were operated on by skull-base surgeons who were at the beginning of their careers.…”

Current Management of Large Vestibular Schwannomas for NF2 Patients in a National Reference Center

“…28,31,36 Accordingly, 57% of VS resections were GTR or NTR, with no gadolinium enhancement on postoperative MRI, although STR and partial planned resections were more frequently performed than for sporadic VS to preserve as much facial and hearing function as possible. 28,31 A good facial function outcome was achieved in 81.5% of large NF2-related VS, which compared favorably with an average of 20% in the literature when GTR are mostly performed. 7,8 Previously in our center, before the application of the functional surgery concept, a good facial function was achieved in only 35% of 72 large NF2-related VS with GTR/NTR between 1998 and 2011 (unpublished data).…”

“…The degree of VS resection was guided by intraoperative facial nerve monitoring at supramaximal stimulation intensity, indicating the facial nerve status during surgery as previously described. 31 If indicated, hearing rehabilitation was performed with CI or ABI.…”

Therapy of Sporadic and NF2-Related Vestibular Schwannoma

“…The surgical outcome in sporadic VS is associated with the following factors: tumor size, adhesion to the brainstem and CNs, the use of CN monitoring technology and surgeon's experience [64][65][66][67][68][69]. Surgical treatments include subtotal resection (STR), near-total resection (NTR) and total resection [70]. Total resection provides a higher rate of long-term tumor control.…”

“…Thus, planned STR and NTR are applied more frequently and provide favorable preservation and recovery of FN function. If residual tumor grows during the follow-up radiotherapy is a good option [70,72]. In few cases, the tumor will continue to grow and requires a secondary treatment [73][74][75].…”