Balance dysfunction and recovery after surgery for superior canal dehiscence syndrome

Objective: To characterize (1) the impairment and recovery of functional balance and (2) the extent of vestibular dysfunction and physiological compensation following superior canal dehiscence syndrome (SCDS) surgical repair. Design: Prospective study. Setting: Tertiary referral center. Participants: Thirty patients diagnosed as having SCDS. Interventions: Surgical plugging and resurfacing of SCDS. Main Outcome Measures: Balance measures were assessed in 3 separate groups, each with 10 different patients: presurgery, postoperative short-term (<1 week), and postoperative long-term (≥6 weeks). Vestibular compensation and function, including qualitative head impulse tests (HITs) in all canal planes and audiometric measures, were assessed in a subgroup of 10 patients in both the postoperative short-term and long-term phases. Results: Balance measures were significantly impaired immediately but not 6 weeks after SCDS repair. All patients demonstrated deficient vestibulo-ocular reflexes for HITs in the plane of the superior canal following surgical repair. Unexpectedly, spontaneous or post-head-shaking nystagmus beat ipsilesionally in most patients, whereas contrabeating nystagmus was noted only in patients with complete canal paresis (ie, positive HITs in all canal planes). There were no significant deviations in subjective visual vertical following surgical repair (P =.37). The degree of audiometric air-bone gap normalized 6 weeks after surgery. Conclusions: All patients undergoing SCDS repair should undergo a postoperative fall risk assessment. Nystagmus direction (spontaneous and post-head-shaking) seems to be a good indicator of the degree of peripheral vestibular system involvement and central compensation. These measures correlate well with the HIT.