Vestibular autonomic regulation (including motion sickness and the mechanism of vomiting)

Autonomic manifestations of vestibular dysfunction and motion sickness are well established in the clinical literature. Recent studies of 'vestibular autonomic regulation' have focused predominantly on autonomic responses to stimulation of the vestibular sense organs in the inner ear. These studies have shown that autonomic responses to vestibular stimulation are regionall y selective and have defined a 'vestibulosympathetic reflex' in animal expe riments. Outside the realm of experimental preparations, however, the impor tance of vestibular inputs in autonomic regulation is unclear because contr ols for secondary factors, such as affective/emotional responses and cardio vascular responses elicited by muscle contraction and regional blood poolin g, have been inadequate. Anatomic and physiologic evidence of an extensive convergence of vestibular and autonomic information in the brainstem sugges ts though that there may be an integrated representation of gravitoinertial acceleration from vestibular, somatic, and visceral receptors for somatic and visceral motor control. In the case of vestibular dysfunction or motion sickness, the unpleasant visceral manifestations (e.g. epigastric discomfo rt, nausea or vomiting) may contribute to conditioned situational avoidance and the development of agoraphobia. Curr Opin Neurol 12:29-33. (C) 1999 Li ppincott Williams & Wilkins.