Neuropsychiatric observations of proprioceptive sensitivity in motion sickness susceptibility.

The assessment of motion sickness susceptibility is still an unsolved problem, due in part to its unclear etiology. We studied 16 referred patients suffering from "idiopathic motion sickness" and 4 pilots suffering from motion airsickness. All clinical and neurological tests proved negative, including electroencephalograms, electronystagmograms, Doppler studies, and computerized tomography of the brain. Cervical spine X-rays and personality characteristics were assessed. Simultaneously, 35 asymptomatic pilots and pilot applicants were studied as controls. Both groups were exposed to cross-coupled accelerations on a Barany chair at 15 rpm along with 0.5 Hz head flexions. The pathological group showed a straightened cervical curvature as well as a significantly higher degree of malaise (scale of Graybiel and Lackner). Their personalities were highly alexithymic or obsessive compared to the control group (Kruskal-Wallis Test). Alexithymic and obsessive personalities may express their stress reactions and psychic conflicts through somatic signs, such as cervical muscle contractures; consequently, straightening the cervical spine with the subsequent alteration of proprioceptive inputs to the vestibular nuclei may increase motion sickness susceptibility.