Vestibular schwannomas are benign lesions of the ponto-cerebellar angle that are potentially dangerous because of their growth in a cramped space and the compressive phenomena they can cause. Stereotactic Gammaknife radiosurgery is a treatment option that can be offered for evolutive schwannomas smaller than 2.5-3 cm in size. It allows tumor stabilisation in 85% of cases with less than 1% facial nerve damage risk.

There are controversial results regarding hearing preservation : percentages vary between 25 and 80% in the literature, depending on the criteria used and the post-treatment delay.

Few studies have investigated changes in vestibular function and the impact on balance of radiosurgery, and their results are variable.

These controversial results lead us to comprehensively assess the vestibular function and balance of these patients using a balance-specific quality of life questionnaire, in addition to objective overall vestibular assessments of vestibular function.

Vestibular schwannomas are benign lesions of the ponto-cerebellar angle that are potentially dangerous because of their growth in a cramped space and the compressive phenomena they can cause. Stereotactic Gammaknife radiosurgery is a treatment option that can be offered for evolutive schwannomas smaller than 2.5-3 cm in size. It allows tumor stabilisation in 85% of cases with less than 1% facial nerve damage risk.

There are controversial results regarding hearing preservation : percentages vary between 25 and 80% in the literature, depending on the criteria used and the post-treatment delay.

Few studies have investigated changes in vestibular function and the impact on balance of radiosurgery.Their results are heterogeneous, on one hand, indicating little worsening of symptoms, or even improvement in some studies. On the other hand, a 2017 study reported symptomatic worsening of caloric response deficits in 17.6% of cases. Vestibular function at high frequencies or for otolithic organs (utricle and saccule) has hardly ever been explored.

The largest cohort, reported in "gammaknife radiosurgery for vestibular schwannomas a quality of life evaluation" concerns 353 patients and shows that the overall quality of life of the patients treated is on average comparable to that of the general population but that the vertigo is more frequent in this population, with a more marked impact on the overall quality of life.

These controversial results lead us to comprehensively assess the vestibular function and balance of these patients using a balance-specific quality of life questionnaire, in addition to objective overall vestibular assessments of vestibular function.

Thus, the present study aims to assess the quality of balance of patients treated with Gammaknife radiosurgery for vestibular schwannoma at 1 year and 3 years after treatment.

Inclusion Criteria:

• Vestibular schwannoma's Patients for whom an indication of gammaknife radiosurgery was determined in a dedicated multidisciplinary consultation meeting, having not received previous treatment for this schwannoma.
• Patient affiliated to Social Security
• No opposition to participation

Exclusion Criteria:

• History of prior treatment for the presented vestibular schwannoma (surgery, fractional radiotherapy)
• History of otological or otoneurological pathology associated with schwannoma
• Patient with type 2 neurofibromatosis
• Patient under legal protection
• Pregnant or breastfeeding women