Editorial: Facial nerve and acoustic neuromas

Abstract

The authors provide a comprehensive assessment of facial nerve function outcomes after using a multimodality approach to vestibular schwannoma (VS) management.1 For larger tumors, they performed either a grosstotal resection (GTR) or a subtotal resection (STR)—with a “facial nerve–sparing paradigm”—followed by Gamma Knife surgery (GKS) if recurrence was identified. For smaller tumors, GKS was performed. One hundred fiftyone patients had an initial “nerve-sparing” resection via a retrosigmoid approach, with the goal of > 90% resection without facial nerve compromise; hearing preservation was not the primary goal. Intraoperative electrophysiological monitoring was used to determine the need for an STR. When > 0.3 mA of stimulation or an increase of ≥ 0.1 mA above baseline stimulation occurred, then resection was stopped. If the facial nerve was in the porus acusticus and thought to be at risk, then the auditory canal was not drilled out. In other patients, GTR was performed. Within this group, 55 patients had complete removal of the tumor with no residual lesion. In the remaining 96 patients, an STR (> 90% volume) was achieved. Significant regrowth was defined as residual tumor fragment expansion by at least 5 mm on the postoperative side. These authors studied a cohort of 20 patients from this group who received GKS. From the complete group of 232 patients who underwent GKS, 3 (1.3%) required further tumor management, which is in line with other series. Interestingly, 8 patients had tumors that varied in size between 1.8 and 2.1 cm, and underwent resection due to what they described as severe symptoms such as vertigo. The authors believed that resection was a better option than GKS, despite the fact that matched cohort studies do not support this conclusion. Outcomes for vertigo or tinnitus in patients treated using either the microsurgical or radiosurgical approach have been similar in several matched cohort studies.2 Of the 20 patients who had GKS after resection, facial nerve function (House-Brackmann Grade I or II) was preserved in 19 (95%). The authors contend that this multimodal approach can lead to improved facial nerve preservation rates, as opposed to attempting GTR in all patients with larger tumors. I agree with this conclusion. Indeed, many centers have begun to use a staged resection followed by radiosurgery in cases in which the intraoperative findings argue against a more aggressive resection along the course of the facial nerve. This report shows that this concept can be associated with good facial nerve functional outcomes. It is important, however, to know that hearing preservation was not the primary management goal, and thus conclusions related to hearing cannot be gleaned from this report. There are several remarks made in this report that warrant some discussion. First, the authors describe waiting for 5 mm of growth before recommending radiosurgery for a “recurrent tumor” after the first resection. Many surgeons would use radiosurgery much earlier, as part of a planned approach several months after the resection for the residual remnant. Although the authors may think that in some cases the remnant has been devascularized or biologically altered in some way, most of these remnants, when truly nodular in shape, do regrow. This is clearly different from the appearance of linear enhancement left along the auditory canal, which may not be viable tumor. Second, in their conclusions they noted that “Stereotactic radiosurgery is inadequate for controlling large tumors, and surgery is often necessary.” This statement is quite broad and not completely supported by the literature. Our own data on tumors between 3 and 4 cm showed that surgery was sometimes necessary, typically for persistent symptoms, but that radiosurgery could indeed be an acceptable approach for individual patients with specific goals.3 The authors state that their facial nerve–sparing technique provides a low incidence of tumor regrowth requiring treatment (13.2%). It is important to know that this was not with long-term follow-up and was based on an extremely conservative definition of “growth.” The second procedure was performed at an average of 3.9 years following resection (range 0.5–7.7 years). In summary, this excellent article from an experienced surgical team under Dr. Sisti clearly delineates the benefits of multimodality surgical management for lesions in patients with larger VSs when intraoperative findings argue against GTR.