Evoked potentials during active horizontal head rotations in patients with vertigo.

Objectives: The purpose of this study was to investigate whether evoked potentials by active head rotation help to verify and topographically differentiate patients with the major symptom vertigo. Methods: Twenty-four healthy human subjects and 43 patients with either infratentorial or supratentorial brain lesions were analysed. Results: The evoked response in normal subjects was composed of six peaks, indicated by polarization and time difference from the trigger points P100, N30, P0, N50, P155 and N320. The EEG pattern was independent of the direction, type of target and whether the eyes were open or closed. In contrast, the evoked response, especially P155, was dependent on the chosen trigger point and acceleration. P155 was the most stable and significant component of the evoked potentials. Thus, we chose P155 as the reference for studying patients with vertigo. Discussion: In peripheral vestibular disorders, cerebellar and diffuse supratentorial cerebral lesions and P155 latencies remain non-significantly altered. However, P155 latencies significantly increase in pontine lesions homolaterally, and space occupying tumors contra laterally. Conclusion: Active horizontal head rotations differentially stimulate the vestibulocortical pathways and may contribute to the analysis of vertigo.