Lesions of the lateral parolivary area of the medulla oblongata, such as occur in the syndromes described by Avellis,1 Wallenberg,2 Babinski and Nageotte3 and Cestan and Chenais,4 were after Wallenberg's5 work generally regarded as due to occlusion of the posterior inferior cerebellar artery. Breuer and Marburg,6 however, pointed out that similar lesions may be produced by thrombosis of the vertebral artery distal to the point of origin of the posterior inferior cerebellar artery or by that of the basilar artery, a fact which was confirmed by the extensive studies of Stopford.7 In 1925 Foix, Hillemand and Schalit8 described a new artery, the arteria fossae lateralis bulbi, and brought substantial evidence to demonstrate that most lesions of the lateral parolivary area (Ziehen9), including part of the dorsal lamella of the inferior olive and the descending root of the trigeminus nerve and its