Sensory interaction testing in platform posturography

Abstract

Mostly techniques measuring the vestibulo-ocular reflex (VOR) have been used for the evaluation of patients with dizziness problems. Some investigators, however, have also tried to take into account the vestibulospinal reflex (VSR). So recording techniques for the Romberg-test have been proposed and called posturography (PG). By interfering with the visual and proprioceptive sensory inputs during this PG-testing one tries to find out how ‘sensory interaction’ is organized in the balance performance of the patient examined. To interfere with vision, closure of the eyes has been commonly used and to interfere with proprioception, the patient can be put on foam-rubber, which makes the contribution of the foot-ankle proprioception less adequate. These interferences are applied once separately and once combined. The degree of ‘abnormality’ is assessed by a score-system for parameters surface (S) and velocity (V), which measure the postural sway. A comparison of tests with and without influence on the sensory inputs gives an idea of the sensory interaction. Patients with peripheral vestibular disorders were examined: patients with BPPV, with spontaneous vertigo attacks and with a sudden vestibular deficit.When applying this evaluation technique different formulae or patterns can be found. Firstly complete normal evaluation, which means that there is no influence of the vestibular disturbance upon the PG results. Secondly a normal balance when using all available sensory information, but disturbed balance as soon as one of the sensory inputs is influenced by the test conditions. Thirdly striking destabilization when closing the eyes. Fourthly striking destabilization when misleading the ankle and foot proprioceptor. Fifthly a combined effect, when the vestibular input is the only one not influenced by the test conditions and sixthly no specific effect, no complementary compensatory effect of this sensory interaction.In the group of patients with peripheral vestibular disorders, no special pattern linked to a peripheral syndrome could be found. Not only in the acute stage could abnormal PG be found: in fact, PG provides ‘functional’ data, which are complementary to the ‘classical’ evaluation and subdivide the patients into other sub-categories. The sensory interaction testing points to some conditions where balance will be more inclined to be troubled.