Does the Presence of Cystic Change Alter the Facial Nerve Prognosis in Surgically Treated Large Acoustic Neuromas?

Objective: This article aims to evaluate facial nerve outcomes after excision of large vestibular schwannomas, and compare the results cystic vestibular schwannomas (CVS) versus solid vestibular schwannomas (SVS).

Materials and Methods: A retrospective chart review of archived surgical cases performed at a single tertiary care institution from January 1, 2006, and December 31, 2013 were identified. Tumors identified as greater than 2.5 cm in diameter were included, and cystic change was defined by greater than 50% fluid-filled tumor on preoperative MRI. Main outcome measures included facial nerve function measured on the House-Brackmann (HB) scale in the early (within 1 week) and late (greater than 6 months) postoperative period. Cases were excluded if the preoperative MRI scan was unavailable or missing data, and in cases of recurrent tumor or previous radiation exposure.

Results: A total of 52 patients with large vestibular schwannomas (41 SVS and 7 CVS) were identified in the 8-year period reviewed, with an even split of men and women. Overall, 48 patients met inclusion criteria and were included in the analysis. All but five operations were performed via the translabyrinthine approach, with three excised via the suboccipital approach, and two requiring a combined translabyrinthine/suboccipital approach. The mean maximal tumor diameter was 3.0 cm for the SVS group versus 3.1 cm for the CVS group.

Preoperative facial function was HB grade I or grade II in all patients, and patients with CVS presented more often with HB grade II than SVS (29% CVS vs.1% SVS). Immediate postoperative facial nerve grade ranged from HB I to HB VI in each group. In the immediate postoperative period, 20 of 41 patients with an SVS (49%) and 3 of 7 patients with CVS (43%) had an HB grade IV or greater. Long-term facial nerve outcomes at 6 months and 1 year follow-up were better in the SVS group, with all but 6 of 41 patients (85%) achieving a favorable HB grade of III or better, versus the CVS group where there was no recovery to a favorable outcome those that were graded as HB grade IV or greater in the immediate postoperative period.

Conclusion: There does not appear to be a large difference in facial nerve outcome in cystic versus solid large-sized vestibular schwannomas when careful dissection of the facial nerve is performed. Facial nerve outcomes may be worse in the long-term follow-up period, although more data are required to show a significant difference.