[Vascular accidents of the brain stem]

Cerebrovascular accidents (CVA's) of the brain stem have the same causes and physiopathological mechanisms as CVA's of the hemispheres, but they are ten times less frequent. They correspond to ischaemic or haemorrhagic lesions in the territories of the vertebral arteries and the basilar artery, including their collateral, circumferential and perforating branches. Clinically, CVA's of the brain stem are characterized by the association of unilateral motor and/or somatosensory symptoms on the side opposite the lesion, and by involvement of the ipsilateral cranial nerves, which helps in evaluating the level of the CVA. Motor or somatosensory symptoms may be bilateral or on alternate sides. The complexity of these CVA's reflects the rich anatomical organization of the brain stem. Their severity in case of extensive lesions is due to the fact that they affect structures that are vital to consciousness and cardiorespiratory regulation. Patients with CVA's of the brain stem must be hospitalized in neurology departments.