Does semicircular canal radiation increase the risk of new vestibulopathy after Gamma Knife radiosurgery for vestibular schwannoma?

BACKGROUND

Vestibular schwannoma Gamma Knife radiosurgery (GKRS) achieves high tumor control rates but is occasionally associated with the new onset of acute vestibular dysfunction. The potential association of vestibulopathy and radiation delivery to the semicircular canals (SCCs) during GKRS has not been explored.

METHODS

We performed a retrospective single-center study of 286 patients who underwent vestibular schwannoma GKRS. Baseline clinical, treatment, and dosimetric data were analyzed. The primary endpoint was the new onset of acute imbalance, vertigo, and/or dizziness within 7 days of radiosurgery. Logistic regression, receiver operating characteristic analysis, and exploratory threshold analyses were performed to evaluate the association between SCC dose and vestibulopathy risk.

RESULTS

SCC maximum dose was the dosimetric parameter most strongly associated with this acute symptom complex. In univariable logistic regression, SCC maximum dose showed an odds ratio (OR) of 1.10 per 1-Gy increase (95% CI 0.98-1.22, p = 0.048); in multivariable analysis adjusted for age, prescription dose, and prior treatment, the association remained borderline (OR 1.10, 95% CI 0.98-1.24, p = 0.098). Patients receiving SCC maximum dose ≥ 10.5 Gy had higher incident vestibular symptom rates than those receiving < 10.5 Gy (34.5% vs. 17.6%; OR 2.46, p = 0.040), and similar findings were observed at ≥ 11 Gy (37.5% vs. 17.7%; OR 2.79, chi-square p = 0.026.

CONCLUSIONS

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.

CLINICAL TRIAL NUMBER: Not applicable.