Early adaptation and compensation of clinical vestibular responses after unilateral vestibular deafferentation surgery

OBJECTIVE: To describe vestibulo-ocular function in the immediate postoperative period after unilateral vestibular deafferentation from vestibular schwannoma resection. STUDY DESIGN: Prospective longitudinal study. SETTING: Tertiary medical center. PATIENTS: Five patients who underwent vestibular schwannoma resection via retrosigmoid approach. INTERVENTIONS: Bedside video-oculography and video head impulse testing (HIT). MAIN OUTCOME MEASURES: Static and dynamic measures of vestibulo-ocular reflex (VOR) function including spontaneous nystagmus, skew deviation, VOR gain during HIT, and presence of saccades related to HIT. RESULTS: Mean ipsilesional horizontal VOR gain decreased from 0.88 ± 0.09 preoperatively to 0.27 ± 0.20 on POD 2 (p = 0.004). Mean contralesional VOR gain declined from 0.95 ± 0.1 preoperatively to 0.79 ± 0.17 on POD 2 (p = 0.032). By POD 4, ipsilesional VOR gain remained low, whereas contralesional VOR gain returned to baseline. Initially on POD 1 to 3, compensatory saccades occurred exclusively after the head stopped moving (overt) with latency of 192.8 ± 36.1 ms; by POD 5, saccade latency decreased to 134.5 ± 23.5 ms (p = 0.026), and saccades were occurring during the head rotation. Skew deviation was present and remained abnormal through POD 5 in 3 of the 5 patients. CONCLUSION: In the postoperative period, gaze stability seems to improve from contralesional VOR gain restoration and reduced latency of compensatory saccades.