Why do we need preliminary procedures to VNG?
The vestibular and visual systems act in synergy to ensure the stability of the images on the retina during the movements of the head and/or the environment with respect to the subject (visovestibular cooperation). Each of them expresses its maximum functional efficiency within different stimulation frequency ranges: the vestibular between 1 and 5Hz, the visual below 1Hz.
The correct analysis of vestibular function is conditioned by two elements. The first element is the oculomotor system which is the efferent arm of the motor responses in relation to adequate sensory stimulations which is not affected by its system pathology. The second element, makes it possible to eliminate all visual information that act by stabilizing the retinal image at the level of the fovea.
The study of oculomotricity is therefore an indispensable prerequisite in the evaluation of balance disorders. Only the normality of its sensory and motor functions allows one to perform a correct visual calibration in amplitude, which is the fundamental operation of vestibulometry that determines the accuracy of the measurements. The presence of an oculomotor pathology also needs to be characterized with precision in relation to: it’s sensorial or motor nature, whether it is a unilateral or bilateral condition. Appropriate variations must be adopted not only in the strategy of carrying out the calibration, but also in the interpretation of the results provided from all diagnostic tests.
Please watch these courses for more information, Vestibular and Balance Assessment in Children with Sensorineural Hearing Loss: An Overview and Recent Advances in the Diagnosis and Treatment of Meniere's Disease.