Stroke

For a lay person:

A stroke is a medical emergency often called a “brain attack.” It happens when the blood supply to part of the brain is suddenly interrupted — either because a blood vessel gets blocked by a clot (the most common type) or because a blood vessel bursts and bleeds into or around the brain. Without fresh blood, brain cells start dying within minutes. This can cause sudden symptoms like one-sided weakness or numbness, drooping face, trouble speaking or understanding, vision loss, dizziness, or severe headache. The effects depend on which part of the brain is affected and how long it goes without blood. Quick treatment can save lives and reduce disability. Many people recover well with fast medical care and rehabilitation.

For a trained medical person:

Stroke is defined as an acute neurological dysfunction attributable to focal injury of the central nervous system (CNS) — brain, spinal cord, or retina — due to a vascular cause. Per the 2013 AHA/ASA expert consensus (still the current standard framework):

• Ischemic stroke / CNS infarction: Brain, spinal cord, or retinal cell death attributable to ischemia, based on neuropathological, neuroimaging, and/or clinical evidence of permanent injury. Clinically, it presents as an episode of neurological dysfunction caused by focal cerebral, spinal, or retinal infarction.
• Hemorrhagic stroke: Includes intracerebral hemorrhage (ICH) and subarachnoid hemorrhage (SAH) due to rupture of a blood vessel.
• Stroke, not otherwise specified: Acute neurological dysfunction presumed to be caused by ischemia or hemorrhage, persisting ≥24 hours or until death, without confirmatory imaging/pathology.
• Silent CNS infarction: Imaging or neuropathological evidence of infarction without recognized acute neurological symptoms.

Key distinctions:

• Transient ischemic attack (TIA): Transient episode of neurological dysfunction caused by focal ischemia without acute infarction on imaging.
• Classification: Ischemic (~87%) vs. hemorrhagic (~13%). Ischemic subtypes include large-artery atherosclerosis, cardioembolism, small-vessel occlusion, other determined etiology, and undetermined (TOAST criteria). Hemorrhagic includes hypertensive, amyloid angiopathy, aneurysmal, AVM, etc.

Diagnosis: Urgent non-contrast CT (to rule out hemorrhage), followed by MRI (DWI for acute ischemia), vascular imaging (CTA/MRA), ECG, labs (glucose, coagulation, lipids), and cardiac monitoring. Time is critical (“time is brain”); eligible patients receive IV thrombolysis (alteplase/tenecteplase) within 4.5 hours or endovascular thrombectomy up to 24 hours in selected large-vessel occlusions. Secondary prevention addresses risk factors (hypertension, atrial fibrillation, carotid stenosis, etc.). Long-term sequelae include motor/sensory deficits, aphasia, dysphagia, cognitive impairment, depression, and increased seizure risk.