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.