Objective: Gamma Knife radiosurgery (GRKS) is a well-established primary, adjuvant, or salvage
treatment for vestibular schwannoma (VS) with low rate of complications including
facial nerve palsy. Whether prior surgical resection affects the facial nerve risk
after GKRS, however, is poorly understood. This study is to investigate post-GKRS
facial nerve function in VS patients who have had prior surgical resection.
Methods: A database of 697 GKRS for adult VS between 2003 and 2024 was screened to identify
specifically cases who received open surgical resection of the same tumor before GKRS.
Demographic, clinical, and radiological characteristics of each tumor were recorded.
Facial nerve function was graded with House Brackmann (HB) scale at multiple time
points: pre-surgery, immediate postop, short-term postop (<3 months), pre-GKRS and
post-GKRS until last follow-up. Descriptive statistical techniques were used to describe
distributions and logistic regression was conducted to assess the relationship between
covariates and post-GKRS facial nerve function.
Results: There were 38 patients with 39 tumors in total were included. Median age was 57 years
(IQR 45–65). The majority (57.9%) of patients were female and tumors were more commonly
right-sided (59%). Eight (20.5%) tumors had cystic changes pre-GKRS. Median time interval
from prior surgery to GKRS was 3 years [MOU2] [JM3] (IQR 0–9). Median tumor volume
at GKRS was 1.96 cc (IQR 1.13–3.40), with a median treatment dose of 13 Gy. [MOU4]
[JM5] Median post-GKRS follow up (f/u) time was 4 years (IQR 2–7), with 1 (2.6%) patient
lost to f/u [MOU6] [JM7] . The facial nerve function at GKRS was HB-I in 24 (61.5%),
HB-II in 5 (12.8%), HB-III in 4 (10.3%), HB-IV in 2 (5.1%), HB-V in 1 (2.6%), and
HB-VI in 3 (7.7%) patients. Facial nerve function was improved in 3 (7.9%), the same
in 28 (73.7%), and worsened in 7 (18.4%) patients within 2 years after GKRS. At last
follow-up post-GKRS, facial nerve function was improved in 6 (15.8%), unchanged in
25 (65.8%), and worsened in 7 (18.4%) patients. No statistical correlation was observed
between change in post-GRKS facial nerve function and age, sex, tumor location, time
between surgery and GKRS, tumor volume at GKRS, or facial nerve grade at GKRS.
Conclusion: In patients with prior surgical resection, the rate of worsened facial nerve function
was 18.4% after GKRS both at 2 years and long-term follow-up. Compared to historical
literature, prior surgical resection appears to be a risk factor [MOU8] [JM9] for
post-GKRS new/worsened facial nerve palsy in adult VS. Further investigation with
larger samples sizes is needed to further delineate specific patient or tumor specific
predictors of worsened facial nerve function post-GKRS.
