The map of dizziness in vestibular schwannoma.

INTRODUCTION: Dizziness is a frequent complaint in patients with vestibular schwannoma (VS). An abnormal vestibulo-ocular reflex (VOR) can explain this dizziness in patients with VS. The video Head impulse test (vHIT) offers a chance to describe specifically the VOR findings in such patients.

STUDY DESIGN: Retrospective cases series study in a tertiary referral hospital.

METHODS: Fifty consecutive patients with VS were classified in accordance with the morphology of the VOR; gain, covert saccade, and overt saccade were analyzed both in the affected side and in the healthy side. For all patients, caloric tests were performed. All patients were tested before surgery.

RESULTS: Caloric response was normal in 31 of 50 patients. The video Head impulse test was abnormal in 45 of 50 patients. For the affected side, low horizontal VOR gain was found in 27 of 50 patients, covert saccade was observed in 37 of 50, and overt saccade was observed in 26 of 50. In the healthy side, vHIT was abnormal in 29 of 50 patients, with a low gain in four of 50, covert saccade in seven of 50, and overt saccade in 23 of 50. In VS, gain for the affected side is not associated with caloric response, but gain for the affected side is associated with gain in the healthy side. Covert and overt saccade for the affected side is associated with gain for the affected side. In the healthy side, overt saccade is associated with low gain for the affected side.

CONCLUSIONS: Video head impulse test improves the vestibular testing before surgery in patients with VS and should be included in the usual clinical tests for these patients.

LEVEL OF EVIDENCE: 4.