Sensory interaction posturography in patients with benign paroxysmal positional vertigo.

BPPV (benign paroxysmal positional vertigo) is a very common peripheral vestibular disturbance. The dysfunction becomes manifest mainly by vertigo and typical nystagmus. However, the vestibulospinal reflex (VSR) can also be disturbed. This can be shown by the SPGIII (static posturography type III), which is a platform technique evaluating 'sensory interaction' in a way comparable to that of the Equi-test. Half the patients with BPPV show disturbed posturographic results. By interfering with the sensory input of vision and/or proprioception, the separate contribution of each input can be evaluated. Different 'formulae' are seen, from complete normal results, through 'overall' formulae, i.e. an undifferentiated influence in all test-conditions, to specific formulae, where we find 'eye-closure' and 'head retroflexed'-effect and so-called 'vestibular formulae'. These formulae are an expression of the different degrees of compensation achieved by the centres and especially of the 'substituting' compensation by vision and proprioception. These results confirm that posturography does not provide a typical results-pattern, thus the type of peripheral vestibular disorder cannot be diagnosed by it alone. The results give functional information on how the standing position is achieved in these patients with a disturbed VSR-input. The several formulae prove that indeed different compensatory patterns are possible, as has been shown by experiments on vestibular compensation.