The vestibulo-ocular reflex and subjective balance after vestibular schwannoma surgery.

OBJECTIVES/HYPOTHESIS: To evaluate the vestibulo-ocular reflex and its relationship with subjective balance in a long-term follow-up after vestibular schwannoma surgery.

STUDY DESIGN: Retrospective cohorts study in a tertiary referral hospital. Forty-nine consecutive patients on which vestibular schwannoma surgery was performed at least 1 year before.

METHODS: Patients are classified in accordance with the morphology of the vestibulo-ocular reflex (VOR) into two groups: Group A, in which covert and overt saccades always occur in an organized fashion; and group B, in which covert and overt saccades randomly occur during head impulse and once finished. We evaluate the presence of covert and overt saccades and the morphology of the VOR measured by the video head impulse test (vHIT) and its relationship with subjective balance measured by Dizziness Handicap Inventory (DHI).

RESULTS: The group B patients returned a higher score in total DHI and all three subscales without any predominant subscale (P = 0,0002; t test). Group B patients were older than those in group A (P = 0,024; t test). No differences were found in sex distribution, tumor size, or side or time interval after surgery. Regarding the unaffected side, overt saccades were found to be more frequent in group B patients (P = 0.05; X(2)).

CONCLUSIONS: Long-term follow-up after vestibular schwannoma surgery has shown that 22% of the patients display a particular abnormality in the VOR because refixation saccades occur in a random fashion after elicitation of the reflex in the HIT test. These patients report the higher level of vestibular disability and handicap.

LEVEL OF EVIDENCE: 2b.