[Electronystagmography aspects of peripheral and central vestibular syndromes]

This report deals with what is to be known in applying ENG in the everyday office. From vestibular, visual and proprioceptive informations central neural processing evolve to stabilize images on the retina. ENG can perform an analysis of these systems, alone or interacting. Anatomical, neurophysiological backgrounds and experimental pathophysiology results are first described. The methodic rule of anamnesis is emphasized and the non instrumental examination is outlined. Concerning the technical aspects and the ENG achievement, some nonlinearities are stressed. Next, procedure of eye movements recording, oculomotor and vestibular testing are described. Alertness, stimulation order, gaze direction and drugs influence the response. The nystagmus responses are evaluated by quantitative parameters and morphological aspects. The variability of these implies the multiplication of the pathological arguments. Peripheral vestibular disturbances lead to labyrinthine paresis or paralysis and to nystagmus directional preponderance, sometimes alone, often combined. Thermic predominance may be associated and cause of some interpretation difficulty. Diagnosis of central neurological disturbances is submitted to four conditions: only specific criteria selection; complete oculomotor and vestibular testing; graduated conclusions in function of the criteria number; no etiological but only functional or topographical diagnosis. Central vestibular syndromes lead also to labyrinthine weakness or nystagmus directional preponderance but, first at all, to specific criteria who are: saccadic, pursuit and horizontal optokinetic abnormalities, central spontaneous or positional nystagmus, failure of fixation suppression, hyperreflexia, perverted nystagmus, slowing of the nystagmus fast phases, slowing-down of the nystagmus slow phases, anisonystagmus, vertical optokinetic deficits and retraction nystagmus. Finally, these dysfunctions incidence in personal observations with some multi or unifocal central pathologies is described and the correspondent more characteristic findings are outlined.