Brainstem Stroke

Brainstem stroke is the most lethal form of all strokes. Both hemorrhagic and ischemic brainstem strokes account for a significant cause of morbidity and mortality on the global front. An ischemic form has a higher incidence compared to its hemorrhagic brainstem counterpart. Knowledge of brainstem stroke syndromes is prudent for early diagnosis and timely management to ensure better clinical outcomes. The brainstem is composed of the midbrain, the pons, and the medulla oblongata, situated in the posterior part of the brain, connecting the cerebrum, the cerebellum, and the spinal cord. Embryologically, the brainstem develops from the mesencephalon and part of the rhombencephalon, originating from the neural ectoderm. The brainstem is organized internally in 3 laminae: tectum, tegmentum, and basis. Gray matter in the brainstem is found in clusters all along the brainstem, mainly forming the cranial nerve nuclei, the pontine nuclei, and the reticular formation. White matter in various ascending and descending tracts is found primarily on the basis lamina, the most anterior part. The brainstem is responsible for multiple critical functions, including respiration, cardiac rhythm, blood pressure control, consciousness, and the sleep-wake cycle. The cranial nerve nuclei in the brainstem have a crucial role in vision, balance, hearing, swallowing, taste, speech, motor, and sensory supply to the face. The white matter of the brainstem carries most of the signals between the brain and the spinal cord and helps with its relay and processing.  The brainstem vasculature is divided by anatomic structures (ie, medulla oblongata, pons, and midbrain), which are further subdivided into the following arterial territories: Anteromedial:  from the anterior spinal artery and the vertebral artery. Anterolateral: from the ASA and VA. Lateral: from the posterior inferior cerebellar artery. Posterior: from the posterior spinal artery. Anteromedial: from perforating arteries of the basilar artery. Anterolateral: from the anterior inferior cerebellar artery . Lateral zone: from lateral pontine perforators of the basilar artery, anterior inferior cerebellar artery, or superior cerebellar artery. Anteromedial: from the posterior cerebral artery. Anterolateral: from the posterior cerebral artery or a branch of the anterior choroidal artery. Lateral group: from the collicular, choroidal, and posterior cerebellar arteries. Posterior group: from the superior cerebellar, follicular, and posteromedial choroidal artery . Brainstem infarction is an area of tissue death resulting from a lack of oxygen supply to any part of the brainstem. The knowledge of anatomy, vascular supply, and physical examination can be life-saving in the setting of an acute infarct and provide precise diagnosis and management. Time becomes an essential factor in management. Early intervention has shown dramatically reduced morbidity and mortality. The brainstem, accounting for almost one-third of all ischemic strokes, leads to high morbidity and mortality on the global front. The pons are predominantly affected. Medullary infarction accounts for 7% of all ischemic brainstem strokes, with lateral subtypes being the most common. There is a male preponderance with a ratio of 3 to 1. Atherosclerosis and vertebral artery dissections are the most common causes. The pontine infarction can be isolated or present as a subset of a more extensive posterior circulation infarction. Ventral infarcts are the most common subtype. Atherosclerosis of the perforating arteries and occlusion of the basilar artery are the most common causes. This can present as a lacunar variant presenting ubiquitously as pure motor, dysarthria-clumsy hand, ataxic hemiparesis syndrome, and pure sensory stroke patterns. Isolated midbrain infarctions are rare and commonly present with concurrent cerebellum, pons, or thalamus involvement. Dorsal pontine involvement is the most common anatomical site for the location of brainstem hemorrhagic stroke.