Retrospective study of risk of new vestibulopathy after semicircular canal radiation during vestibular schwannoma GKRS

Vestibular schwannoma (VS) gamma knife radiosurgery (GKRS) achieves high tumor control rates but is occasionally associated with onset of new acute vestibular dysfunction. A retrospective study at the University of Pittsburgh (PA) Medical Center evaluated the association of radiation delivery to the semicircular canals (SCCs) during VS GKRS with vestibulopathy in 286 patients. The primary endpoint was new onset of acute imbalance, vertigo, and/or dizziness within 7 days of radiosurgery. SCC maximum dose was the dosimetric parameter most strongly associated with this acute symptom complex. In univariate logistic regression, SCC maximum dose showed an OR of 1.10 per 1-Gy increase (p=0.048); in multivariable analysis adjusted for age, prescription dose, and prior treatment, the association remained borderline (OR 1.10; p=0.098). Patients receiving SCC maximum dose ≥ 10.5 Gy had higher incident vestibular symptom rates than dose receiving ≤ 10.5 Gy (34.5% versus 17.6%; OR 2.46; p=0.040), and similar findings were observe at <11 Gy versus ≥ 11 Gy. The authors conclude that higher SCC maximum dose was associated with increased risk of acute incident vestibular symptoms after GKRS. The 10.5-11 Gy range may represent an exploratory risk threshold but should not be considered a validated dose constraint without prospective validation.