Summary
Highlights
There are two main types of stroke: ischemic (blocked artery) and hemorrhagic (broken artery). Ischemic strokes are more common, and their damage depends on affected brain areas and duration of reduced blood flow. If symptoms resolve within 24 hours, it's a transient ischemic attack (TIA).
The brain includes the cerebrum (divided into frontal, parietal, temporal, and occipital lobes), cerebellum, and brainstem. Each part controls specific functions, such as movement, sensory processing, memory, vision, coordination, and vital bodily functions.
The brain receives blood from the internal carotid and vertebral arteries, which form the Circle of Willis. This arterial ring allows alternative blood flow routes in case of blockage, providing a safety mechanism against diminished blood supply.
Ischemic strokes often result from endothelial cell dysfunction, where irritation (e.g., from tobacco) damages the artery lining, leading to atherosclerosis (plaque formation). Plaque buildup can obstruct blood flow, and rupture of these plaques can cause sudden and complete arterial blockage due to clot formation.
Embolic strokes occur when a blood clot breaks off from one location, travels, and lodges in a smaller artery in the brain. These clots can originate from atherosclerosis or the heart, especially with conditions like atrial fibrillation or after a heart attack. Heart defects can also allow clots from veins to reach the brain.
Lacunar strokes involve deep branches of the middle cerebral artery and result in fluid-filled cysts in damaged brain tissue, often due to hypertension or diabetes. Watershed infarcts occur when overall blood flow diminishes, affecting tissues furthest downstream in the brain, at the border of two different blood supplies.
An ischemic stroke creates an ischemic core (tissue that dies) and an ischemic penumbra (surrounding tissue that can be saved). Lack of glucose and oxygen leads to cell damage, cytotoxic edema, and release of destructive enzymes. Inflammation causes vasogenic edema, and brain swelling can lead to dangerous herniation.
Stroke symptoms vary based on the affected brain area, including numbness, muscle weakness, speech difficulties (Broca's or Wernicke's aphasia), and vision problems. The FAST acronym (Facial drooping, Arm weakness, Speech difficulties, Time) helps recognize common symptoms and emphasizes quick action. Diagnosis involves CT/MRI scans and angiography to locate blockages.
Treatment focuses on reestablishing blood flow quickly using thrombolytic enzymes like TPA (within a time limit) and aspirin. Surgical procedures like MERCI or suction removal can physically remove clots. Prevention involves managing risk factors like smoking, high blood pressure, cholesterol, and diabetes. Surgeries like carotid endarterectomy or stent placement can address severe atherosclerosis.