Abstract
Introduction Gamma Knife radiosurgery (GKRS) is an effective treatment for benign vestibular schwannomas
(VSs). The established cutoffs have recently been challenged, as recent literature
expanded the horizon of GKRS to larger tumors. Even though microsurgery remains the
primary option for large VS, GKRS can provide reasonable tumor control and is more
likely to avoid cranial neuropathies associated with open surgery.
Methods We analyzed patients with VS with volume exceeding 10 cm3 who underwent GKRS at our center from January 2006 to December 2016. Clinicoradiological
and radiosurgical data were collected from medical records for statistical analysis.
Follow-up was performed every 6 months with a clinical assessment along with magnetic
resonance imaging (MRI) of the brain and audiometric evaluation in patients with serviceable
hearing.
Results The study included 34 patients (18 males and 16 females) with an average age of 45.5
years. The mean tumor volume was 10.9 cm3 (standard deviation [SD], ± 0.83), with a median tumor dose of 12 Gy (interquartile
range, 11.5–12) and a mean follow-up of 34.7 months (SD, ± 23.8). Tumor response was
graded as regression in 50%, stable in 44.1%, and increase or GKRS failure in 2 cases
(5.8%). Treatment failure was noted in five cases (14.7%), requiring microsurgical
excision and a ventriculoperitoneal shunt post-GKRS. The tumor control rate for the
cohort is 85.3%, with a facial preservation rate of 96% (24/25) and hearing loss in
all (5/5), while three patients developed new-onset hypoesthesia. We noted that gait
ataxia and involvement of cranial nerve V or VII at initial presentation were associated
with GKRS failure in univariate analysis.
Conclusion Microsurgery should remain the first-choice treatment option for large VSs. GKRS
is a viable alternative with good tumor control and improved or stabilized cranial
neuropathies with a low complication rate.
Keywords
GKRS - large vestibular schwannoma - tumor control rate - predictors of tumor control
