After considering the general symptomatology of lesions of the brain stem, the authors report the clinical observation of six patients presenting vascular syndromes related with the medulla, pons and midbrain, discussing, for each case, the localization and etiopathogeny of the lesion. These observations show the degree of complexity that may be attained by disturbances due to vascular lesions and demonstrate the fact that, in many instances, such disturbances do not correspond to the established syndromes of the medulla, pons and peduncles, since these lesions are often large, multiple and occur at several levels. The authors refer to some of the fundamental data on the blood supply of the brain stem as well as on the etiopathogeny of the lesions, taking into consideration chiefly the arteriosclerosis and syphilis of the basal vessels. There follows a clinical discussion of the thrombosis of the artéria basilaris and the report of a case clinically diagnosed as cerebral hemorrhage (cortico-subcortical or capsular) with inundation of the ventricles, which case the necropsy proved to be thrombosis of the artéria basilaris and softening of the left lateral half of the pons.
