[Oculomotor response to the vertical cephalic autorotatory test in patients with benign paroxistic positional vertigo of the posterior canal].

Objective: To evaluate the eye movement response to the head auto-rotation test (HART) in the vertical plane in patients with benign paroxysmal positional vertigo.
Design: A transversal, descriptive study. SETTING UP: Outpatient clinic in a general Hospital.
Individuals: 34 posterior canal BPPV cases with a video-oculographic diagnosis, older than 18 years old, 7 of them were not able to perform the HART.
Intervention: HART was performed by a an electrooculographic system with simultaneous recording of head movement by an acelerometer in the vertical plane (Vorteq, Micromedical Instruments). The HART with eyes fixation was performed 3 times to determine its reliability.
Main Outcome Measures: Gain, asymmetry and phase for the vertical VOR respectively. A statistical analysis was carried out to determine the test reliability and the number of individuals with an abnormal result.
Results: Gain is the only variable that showed a reproducible result in the HART for the active head movement at 1-2 Hz (test-retest reliability 0.83-0.89). The values of gain showed a moderate correlation at the frequencies 1-3 Hz (correlation 0.60-0.87). Asymmetry and phase were not reproducible variables (correlation < 0.55). Thirteen of 27 (48%) patients presented a decrease of the vertical gain, another 13 showed normal values and one case showed raised values.
Conclusion: Gain is the only useful variable in the vertical HART. Forty-eight percent of patients with posterior canal BPPV have a reduced vertical gain, suggesting an impairment of inferior vestibular nerve function.