Etiology of sudden deafness with positional nystagmus of the direction changing type

We present two patients with sudden deafness and positional nystagmus of the direction changing type in which the nystagmus was directed toward the upper ear with the head in a lateral position. The first case was a 60-year-old man ; the second was a 50-year-old man. Both patient exhibited this type of nystagmus for more than a year. The first patient showed a well developed nystagmus on caloric test and head tremor by gazing. The second patient had accompanying visual symptoms due to circular insufficiency of the posterior cerebral artery. We have often encountered cases of sudden deafness with vertigo or dizziness. In most cases, equilibrium disorder and nystagmus disappeared soon after the recovery of a vestibular function and the compensation of the central nervous system. Some cases of sudden deafness showed positional nystagmus of the direction changing type that directed toward the upper ear with the head in the lateral position. This type of nystagmus was first reported as a characteristic sign of vertigo associated with central nervous disorder. Recently, several papers have reported that some cases of vestibular disorder showed this type of nystagmus which usually changes to an other type or disappears within a short period. Because nystagmus of our two patients remaind unchanged for more than a year, we considered that the causes also participate in the disorder of the central equilibrium system. The anterior inferior cerebellar artery supplies the blood to the vestibulocerebellum and its branch, the labryhthine artery, which also supplies the inner ear. Thus, the function of both the cerebellum and the inner ear would be damaged, in cases involving a disorder of this vessel. In our patients, the cause was a vascular disorder associated with a disorder of both the peripheral and central nervous systems.