A case of transient alternating nystagmus' occurring in association with an organic disease Involving the Posterior Fossa

Abstract

So-called alternating nystagmus (involuntary eye movements in alternating directions) has been reported to occur frequently in congenital nystagmus. Moreover, the differential diagnosis of congenital nystagmus is relatively easy because of its numerous characteristic features, e.g., accompanied often by inverse OKN, devoid of oscillating vision except in the latent form, tending to become pronounced with fixation and diminished on closing the eyes and being a lifelong phenominon.
In describing acquired alternating nystagmus as oposed to the congenital variety, Kornhuber pointed out that it occurs in the presence of extreme vestibular hyperfunction resulting from cerebellar disorders associated with impairment of the roof of the fourth ventricle, or in cases of syringobulbia or multiple sclerosis. The patient presented here had transient alternating nystagmus, presumably due to a similar underlying disease. CT-Scan revealed an abnormality in the posterior fossa. This case is presented in the hope that accumulation of such cases of acquired illnesses will help elucidate the pathogenetic mechanism of congenital alternating nystagmus.