The vestibular system provides inputs to many neurons in the brain ste
m that participate in autonomic control, This multiplicity of vestibul
ar-autonomic connections plays a variety of roles. Whereas it has been
known for decades that unilateral vestibular lesions can result in mo
tion sickness, recent data suggest that the vestibular system particip
ates in making adjustments in blood pressure and respiration that are
necessary to maintain homeostasis during movement and changes in postu
re, Animals with bilateral vestibular lesions are more susceptible to
posturally related hypotension than vestibularly intact animals, and i
t is also possible that orthostatic hypotension after space flight is
caused in part by microgravity-related changes in otolith function. Pa
tients with vestibular lesions could also be more vulnerable to respir
atory disturbances related to posture, such as obstructive apnea. Vest
ibular dysfunction has additionally been linked with anxiety disorders
, such as agoraphobia, which may result from alteration of vestibular
inputs to brain stem monoaminergic neurons (which are known to process
these signals). Even sleep disturbances might be connected with vesti
bular disorders because neurons in the pontine reticular formation tha
t are critical in switching between sleep states may be influenced by
labyrinthine inputs. Thus it is likely that vestibular damage will res
ult in a number of parallel disturbances in autonomic function,