Visuo-vestibular interaction in the otoneurological semiology.

The test-procedure for visuo-vestibular interaction, used in this study, consists in the comparison of the results of a pure vestibular rotation test (V-test), a combined optokinetic and vestibular test (V + O-test) and an optokinetic test (OKN-test), the obtained nystagmus being elicited by a sinusoidal stimulus of 0.05 Hz and 120 degrees ampl. The evaluation of the symmetry in the obtained reactions allows us to distinguish different mechanisms in the achievement of compensation. In case of caloric asymmetry, the presence of an asymmetry in the V-test proves there is still a lack of sufficient compensation at the vestibular level. In some of them, also the V + O-test shows asymmetry, but in most of cases the latter test shows a symmetrical reaction, proving the efficiency of the substitutive interaction of the optokinetic mechanisms in the scope of compensation. In rather rare cases we find an asymmetry only in the V + O - test and then mostly associated with an asymmetry in vestibular tests, others than the V-test. An asymmetry in the OKN-test is mostly a repercussion of the vestibular asymmetry, detected in the other vetibular tests, and in case of a complete vestibular symmetry, it is an indication for central pathology. The diversity of the observed reaction patterns proves the complexity of the mechanisms for compensation in case of vestibular deficiency.