A stroke occurs when neurones of the brain are starved of Oxygen due to impaired or interrupted blood flow. The cells without Oxygen are unable to carry our aerobic respiration and are said to be ischemic.
There are 2 types of stroke, ischemic and hemorrhagic.
An ischemic stroke occurs when the blood vessel is occluded (blocked) due to a clot plugging the blood vessel, this can be caused by a clot building in the brain itself as a result of atherosclerosis (fatty deposition i the blood vessels caused by increased circulating LDLP's) or a clot migrating to the brain in the blood vessels after forming elsewhere -most commonly in the heart. A blockage caused by a clot forming in the brain is called a cerebral thrombosis, a clot that has migrated to the brain is called a cerebral embolism. Treatment for an ishemic stroke must occur within 4 hours since onset otherwise it can cause irreparable damage to the neurones. A clot busting drug called tissue plasminogen activators are infused intravenously into the blood to dissolve the clot and thus restoring the blood flow. Some damage may have occurred to the localised areas of cells, such damage may present as reduced nervous ability. Due to the fluidity of the brain, some damage is reversable as the brain cells make new connections in an attempt to repair itself. 87% of strokes are ishemic strokes.
A hemorrhagic stroke is caused by a rupturing of the blood vessel, allowing a bleed into the brain. The blood compresses the brain and symptoms begin to present. There are 2 types of hemorrhagic stroke, an aneurysm caused by a balloon like weakening of the brain tissue, if left untreated this weakened part of the blood vessel will swell and rupture. The second is a arteriovenous malformation (AVM) and abnormal cluster of blood vessels prone to rupture. Hemorrhagic stroke is problematic due to the slow rise in inter cranial pressure caused by an increase in volume within the cranial vault. A Hemorrhagic stoke is treated using medications including:
Anticonvulsants - To prevent seizure recurrence
Antihypertensive agents - To reduce BP and other risk factors of heart disease
Osmotic diuretics - To decrease intracranial pressure in the subarachnoid space