[Frequency-specific analysis of the hVOR Prior of Cochlear Implant Operation]

Dizziness is one of the most common postoperative complications after a cochlear-implant (CI) surgery. With our prospective, matched-paired controlled study, we could demonstrate that patients with distinctive sensorineural hearing loss--even without any complaints of dizziness--already have a reduced horizontal vestibular-ocular-reflex (hVOR). Compared to controls, CI patients presented with a significantly reduced gain. 9 out of 17 CI patients showed physiological results in rotatory testing and video head thrust testing. One patient presented with pathological results in both tests. Remarkably, there were 2 patients who presented with pathological head impulse testing but normal values in rotatory testing and 5 patients who showed normal gains in video head impulse testing but abnormal rotatory tests. These findings clearly show the importance of a differentiated, frequency-dependent pre-operative vestibular assessment including rotatory testing and video-head impulse testing. Additionally, only an accurate pre-operative vestibular testing allows evaluating possible post-operative dizziness related complications and should be documented precisely, also for forensic reasons. This is the key to differentiate post-operative dizziness from an pre-operatively existing vestibular disorder that possibly might not be clinically apparent by the time of testing.