Strokes can either be due to ischemic or hemorrhagic processes.
Ischemic strokes are caused by interruptions to the blood flow to any region in the brain either due to occlusion of blood flow or due to reduced perfusion. The extent of neurological deficit lies in proportion to the territory involved. Common causes of ischemic stroke are emboli, large or small artery disease states, and various systemic and hematologic disorders. They usually arise due to ischemia in the carotid or the vertebrobasilar arterial distributions. Hemorrhagic strokes are caused by intraparenchymal or subarachnoid hemorrhage.