Changes in patient-perceived balance and vestibular function after Gamma-knife stereotactic radiosurgery for vestibular schwannoma: 12-month outcomes in a single-centre pilot study.

BACKGROUND

Hearing outcomes are well-documented for patients with vestibular schwannoma (VS) treated with Gamma Knife stereotactic radiosurgery (GK-SRS). However, how GK-SRS affects patient-perceived balance and vestibular function remains unclear. This study therefore evaluated changes in these parameters one-year post-treatment.

METHODS

A prospective, observational, before-and-after, pilot study was conducted on patients with unilateral VS treated with GK-SRS between June 2021 and July 2022. Balance-related handicap was assessed using the Dizziness Handicap Inventory (DHI). Objective vestibular function was evaluated through caloric tests and video head impulse tests (VHIT). Data were compared before treatment (0 M) and 12 months after treatment (12 M).

RESULTS

Thirty-eight patients were included (median age 69 years, 52.6% male). Median total DHI scores significantly deteriorated (14 [5; 24] at 0 M vs. 18 [8;40] at 12 M, p = 0.027), with an increase in cases classed with moderate handicap (12%-29%, p = 0.025). We found a significant deterioration in median caloric deficit at low frequency (49 [29; 78]% vs. 72 [40; 87]%; p = 0.012) and a significant deterioration in median vestibulo-ocular reflex (VOR) gain of the anterior semicircular canal (SSC) at high frequency (0.94 [0.86;1.04] vs. 0.9 [0.72;0.98]; p = 0.012). Change in DHI score was only found weakly inversely correlated with change in VOR gain for the affected-side posterior SSC (r = -0.38; p = 0.04).

CONCLUSION

GK-SRS for VS can result in modest deterioration in subjective balance after one year. Changes in DHI were not strongly correlated with objective vestibular function deficits thus suggesting other factors can contribute to dizziness and balance outcomes.