Living with an uncompensated, abnormal vestibular system requires oppr
essive modification of life style and often prevents return to work an
d activities of daily living. Patients with vestibular abnormalities w
ere studied to determine the minimal residual vestibular function requ
ired to achieve compensation. Three groups of patients with (a) comple
te unilateral loss of vestibular function with normal horizontal canal
-vestibulo-ocular (HCVOR) function in the opposite ear, (b) complete u
nilateral loss with abnormal HCVOR function in the opposite ear, and (
c) bilateral reduction of vestibular function from aminoglycoside toxi
city underwent vestibuloocular (VOR), optokinetic (OKN), visual-VOR (V
VOR), and computerized dynamic posturography (CDP) tests before and af
ter therapeutic procedures. Results suggest that a minimal VOR respons
e amplitude must be present for compensation of VVOR function to occur
. The roles of VOR and OKN phase shifts in vestibular compensation are
more complicated and require further study. Compensation of vestibulo
spinal function does not necessarily accompany VOR or VVOR compensatio
n. Ascending and descending vestibular compensatory mechanisms may inv
olve different spatial sensory inputs. Results of these studies have i
mportant implications for the diagnosis and treatment of patients with
vestibular disorders, including selection and monitoring of patients
for therapeutic regimens such as vestibular nerve section and streptom
ycin therapy.