Preserved visual-vestibular interaction in patients with bilateral vestibular failure.
BACKGROUND
During caloric vestibular stimulation, subjects showed bilateral activation of the vestibular cortex in the posterior insula and retroinsular region as well as concurrent deactivation of visual cortex areas bilaterally. This finding was the basis for the concept of a reciprocal inhibitory interaction between the vestibular and the visual systems.


OBJECTIVE
To analyze the modulations of this activation and deactivation pattern in patients with loss of vestibular input, that is, in patients with bilateral vestibular failure (BVF).


METHODS
Modulations of regional cerebral blood flow (rCBF) in PET were measured in nine patients with BVF and compared with those in healthy volunteers using statistical group as well as single-subject analyses (Statistical Parametric Mapping 96b).


RESULTS
The group analysis of the BVF patients showed only one small region of activation in the posterior insula contralateral to the stimulated ear, whereas the other areas correlating with vestibular, autonomic, and ocular motor function were not activated. Furthermore, the concurrent rCBF decreases of the primary visual cortex seen in healthy volunteers were not found in the patients. These decreases seem to be dependent on an intact vestibular input with concurrent vestibular nystagmus.


CONCLUSIONS
The results are compatible with the concept of a reciprocal inhibitory sensorisensory interaction between the vestibular and visual systems that normally act together for orientation in space and perception of motion. This interaction appears to be preserved in the patients at a significantly lower level, that is, with less activation and less deactivation.
Bense
S
S
Department of Neurology, Johannes Gutenberg-University of Mainz, Langenbeckstrasse 1, D-55101 Mainz, Germany. bense@neurologie.klinik.uni-mainz.de
Deutschländer
A
A
Stephan
Th
T
Bartenstein
P
P
Schwaiger
M
M
Brandt
Th
T
Dieterich
M
M
D000328:Adult; D000368:Aged; D002150:Caloric Tests; D002560:Cerebrovascular Circulation; D030141:Feedback, Psychological; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D008959:Models, Neurological; D009759:Nystagmus, Pathologic; D010296:Parietal Lobe / Q000000981:diagnostic imaging / Q000503:physiopathology*; D049268:Positron-Emission Tomography; D012021:Reflex, Abnormal; D012027:Reflex, Vestibulo-Ocular; D013382:Subtraction Technique; D013702:Temporal Lobe / Q000000981:diagnostic imaging / Q000503:physiopathology*; D015837:Vestibular Diseases / Q000000981:diagnostic imaging / Q000503:physiopathology*; D014722:Vestibule, Labyrinth / Q000503:physiopathology*; D014793:Visual Cortex / Q000000981:diagnostic imaging / Q000503:physiopathology*