Video Head Impulse Test (vHIT) Findings in Patients With Superior Semicircular Canal Dehiscence: A Case-Control Study

To explore the usefulness of the responses of video head impulse testing (vHIT) in assessing symptomatic patients with superior semicircular canal dehiscence (SSCD).

This was a prospective case-control study performed in a tertiary skull base referral Centre in the UK. It included all patients ¬diagnosed with SSCD from January 2015 to January 2019 and compared to a control group of age and gender-matched unaffected indi¬viduals. The main outcome of the study was semicircular canal vestibule-ocular reflex (VOR) gains during vHIT assessment and link to patients' symptoms.

A total of 28 patients were diagnosed with SSCD during the study period and completed the vHIT assessment. Reduced VOR gains (<0.8) were noted in 57% of patients (n = 16). Half of these (n = 8) were in canals other than the superior semicircular (posterior only: n = 5; lateral and posterior: n = 3). Three patients (10.7%) had abnormal responses in 2 canals. The canals in the contralateral side were affected in 56.5% of the cases. There was no correlation with the patients' symptoms. Results were directly comparable with the control group vHIT results with no identifiable statistically significant differences on comparison of the ipsilateral SSCD side with a randomly selected side from the control group (all comparisons: P > .05).

SSCD can affect the vestibular responses from all 3 semicircular canals; not necessarily the superior one. Similar responses were found in a control group of normal subjects. Although the use of vHIT in the assessment of SSCD is not diagnosis-specific, it can still help with identifying the impact of surgery on all canals prior to any intervention in order to avoid bilateral vestibular failure.