[Optokinetic reactivity and vestibular disorders of central origin (author's transl)].

An electronystagmographic study of optokinetic reactivity is conducted in 50 'normal' adult subjects and 200 patients suffering from various diseases, all of whom presented an abnormal electronystagmogram. Optokinetic reactivity is evoked by a sudden acceleration of the optokinetic stimulus. It is considered normal when this acceleration leads to an increase in amplitude. At the same time, the frequency of the optokinetic nystagmus decreases. This type of response can be modified by various disorders. Recent cranial trauma and tetany are associated with an incomplete or inadequate optokinetic response; brain vascular diseases and disorders of central origin induce an absence of that response, while some cases of multiple sclerosis and neuro-allergies give rise to an apparently momentary, unstable response. Optokinetic reactivity thus represents an extension of the classical optokinetic test and yields valuable diagnostic clues.