A stroke occurs when blood supply to part of the brain is suddenly interrupted, causing brain cells to begin dying within minutes. It is a medical emergency and a leading cause of death and long-term disability worldwide. Rapid recognition and treatment are critical to minimizing brain damage and improving outcomes — in ischemic stroke, every minute of delay results in the loss of approximately 1.9 million neurons.
Stroke shares symptoms with other serious neurological emergencies and must be distinguished rapidly from conditions including brain aneurysm rupture, subdural hematoma, and traumatic brain injury. Patients with known vascular risk factors — including those with imaging findings of chronic small vessel ischemia or white matter lesions — are at elevated stroke risk and may benefit from surveillance MRI and aggressive risk factor management.
Causes
Ischemic stroke
The most common type, accounting for approximately 87% of all strokes, ischemic stroke occurs when a blood clot or other obstruction blocks an artery supplying the brain. Clots may form locally within a diseased, atherosclerotic artery (thrombotic stroke) or travel from a distant source such as the heart or a proximal artery (embolic stroke). Atrial fibrillation is the most common cardiac source of embolic stroke. Small vessel disease — the same process responsible for chronic small vessel ischemia — causes lacunar infarcts, a distinct subtype of ischemic stroke affecting the deep brain structures.
Hemorrhagic stroke
Hemorrhagic stroke occurs when a blood vessel in the brain ruptures, causing bleeding directly into the brain tissue (intracerebral hemorrhage) or into the space surrounding the brain (subarachnoid hemorrhage). Chronic high blood pressure is the leading cause of intracerebral hemorrhage. Ruptured brain aneurysms are the most common cause of subarachnoid hemorrhage — a catastrophic event with high mortality. Arteriovenous malformations (AVMs) and cavernous malformations are additional vascular lesions that can cause hemorrhagic stroke.
Symptoms
Stroke symptoms appear suddenly and without warning. The FAST acronym captures the most recognizable signs:
- Face: Sudden facial drooping or asymmetry, particularly on one side.
- Arms: Sudden arm weakness or numbness — ask the patient to raise both arms; one drifting downward is a positive sign.
- Speech: Sudden slurred speech, inability to speak, or difficulty understanding language (aphasia).
- Time: Call 911 immediately — time to treatment is the single most important determinant of outcome.
Additional symptoms include sudden severe headache (the "worst headache of your life" — characteristic of subarachnoid hemorrhage from a ruptured aneurysm), sudden vision loss or double vision, severe dizziness or loss of balance, and sudden confusion. Any sudden neurological symptom should be treated as a stroke emergency until proven otherwise.
Diagnosis
Emergency evaluation begins with rapid neurological assessment using validated stroke scales (NIHSS) to quantify deficit severity. Immediate imaging is essential:
- CT scan (non-contrast): Performed first in virtually all stroke patients to rule out hemorrhage — this is mandatory before administering clot-dissolving therapy, as tPA given for hemorrhagic stroke is fatal.
- MRI with diffusion-weighted imaging (DWI): Far more sensitive than CT for detecting early ischemic stroke, identifying infarcted brain tissue within minutes of onset before CT changes appear. DWI is the most sensitive sequence and shows restricted diffusion in acutely ischemic tissue as a bright signal. MRI also identifies the ischemic penumbra — potentially salvageable tissue surrounding the infarct core — which guides decisions about late thrombectomy.
- CT angiography or MR angiography: Identifies large vessel occlusions (LVO) eligible for mechanical thrombectomy, the most impactful acute intervention available.
After acute stabilization, cardiac monitoring (telemetry, Holter monitor), echocardiography, and lipid and coagulation blood panels identify the stroke mechanism and guide secondary prevention strategy.
Stroke Classification
Strokes are classified by mechanism, which directly guides acute treatment and long-term prevention:
- Ischemic — Thrombotic: Clot forming within a diseased, atherosclerotic brain artery. Treated with antiplatelet therapy and aggressive vascular risk factor control.
- Ischemic — Embolic: Clot traveling from the heart (cardioembolic) or a proximal artery to occlude a brain vessel. Anticoagulation is the cornerstone of prevention for cardioembolic stroke from atrial fibrillation.
- Ischemic — Lacunar: Small vessel occlusion causing infarcts in the deep brain structures (basal ganglia, thalamus, internal capsule, pons). Associated with hypertension and small vessel disease.
- Hemorrhagic — Intracerebral: Bleeding directly into the brain tissue, most commonly from uncontrolled hypertension or amyloid angiopathy.
- Hemorrhagic — Subarachnoid: Bleeding into the space surrounding the brain, most commonly from a ruptured aneurysm.
- Transient Ischemic Attack (TIA): Temporary stroke symptoms resolving within 24 hours with no permanent brain injury on imaging — a critical warning sign of impending stroke requiring urgent evaluation and treatment.
Treatments
Acute ischemic stroke:
Intravenous thrombolysis with tPA (tissue plasminogen activator) dissolves the offending clot when administered within 4.5 hours of symptom onset in eligible patients, restoring blood flow before permanent infarction is complete. Mechanical thrombectomy — physically removing the clot using a catheter-based stent retriever device — is highly effective for large vessel occlusions and can be performed up to 24 hours after onset in patients with salvageable penumbra on advanced imaging, dramatically improving outcomes even for patients who arrive late. Together, tPA and thrombectomy represent the most impactful acute neurological interventions available.
Hemorrhagic stroke:
Management focuses on controlling bleeding, reducing elevated intracranial pressure, and reversing any anticoagulant medications contributing to hemorrhage expansion. Blood pressure reduction is initiated urgently. Surgical evacuation of the hematoma, placement of an external ventricular drain for hydrocephalus, or clipping and coiling of a ruptured aneurysm may be required depending on hemorrhage location, size, and cause.
Rehabilitation and secondary prevention:
Comprehensive stroke rehabilitation — physical, occupational, and speech therapy — begins as soon as the patient is medically stable and continues for months to years. The brain retains significant capacity for recovery through neuroplasticity, particularly in the first 3–6 months. Secondary prevention with antiplatelet agents, anticoagulation for cardioembolic stroke, aggressive blood pressure and cholesterol management, diabetes control, smoking cessation, and lifestyle modification is essential — the risk of recurrent stroke is highest in the days and weeks immediately following the first event.
Get an MRI to Confirm Your Diagnosis
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