THE SYNDROME of occlusion of the posterior inferior cerebellar artery was first firmly established by Wallenberg1 in 1895. Prior to that time, there had been several reports strongly suggestive of this syndrome.2 In Wallenberg's studies of the anatomic distribution and variations of the posterior inferior cerebellar artery, he noted that the vessel was often absent on the right side. He stated that a portion of the lateral medullary region is completely devoid of blood supply when the artery is occluded, although a part is supplied by the collateral circulation. The bloodless area includes the restiform body, the direct spinocerebellar tract, the descending root of the trigeminal nerve, the motor nucleus of the vagus nerve (the nucleus ambiguus), a portion of the hypoglossal nucleus and a portion of the cerebellum. With this information, one may predict the clinical features of the syndrome.
The onset is usually sudden, without loss