FAST

Status: current, with caveats. The source library flags this one as still taught but qualified — read the safety notes on each component before relying on it.

A rapid public/community recognition tool for the most common signs of stroke — Face drooping, Arm weakness, Speech difficulty, and Time to call emergency services — to get patients to definitive stroke care as fast as possible.

F — Face drooping

Contralateral facial weakness

Facial droop from damage to the facial motor pathway, most often the corticobulbar fibers to the facial nerve nucleus. In a typical MCA stroke the lower face is most affected, with relative sparing of the forehead.

Physiology. The forehead receives motor input from both brain hemispheres, so a one-sided stroke often spares it; the lower face receives mainly crossed input, so it droops — helping distinguish central (stroke) from peripheral (Bell's palsy) causes.

Safety. Facial droop with other stroke signs needs immediate stroke-pathway activation; do not assume Bell's palsy without excluding stroke.

A — Arm weakness

Contralateral motor deficit

Arm or leg weakness from damage to the motor cortex or corticospinal tract on the opposite side. The classic test is pronator drift (the weak arm drifts downward and pronates). Weakness ranges from subtle drift to hemiplegia.

Physiology. The corticospinal tract crosses in the lower medulla, so the left brain controls the right arm and vice versa; interruption anywhere along the tract causes contralateral weakness.

Safety. Sudden, painless one-sided weakness is a stroke emergency — never dismiss it as 'just a pinched nerve.'

S — Speech difficulty

Dysarthria or aphasia

Speech difficulty includes dysarthria (slurred speech from weakness/incoordination of speech muscles) and aphasia (a language disorder from damage to left-hemisphere language areas). Aphasia is a cortical sign suggesting large-vessel or left-hemisphere stroke.

Physiology. Language is processed mainly in the left hemisphere (Broca's area for expression, Wernicke's area for comprehension); dysarthria results from damage to motor pathways controlling the tongue, lips, and palate.

Safety. Sudden confusion with speech difficulty can be mistaken for intoxication or dementia — always consider stroke and check last-known-well time.

T — Time to call emergency services

Time is brain / last-known-well

Roughly 1.9 million neurons may be lost per minute during a large-vessel stroke. Time-sensitive treatments include IV thrombolysis within ~4.5 hours of last-known-well and mechanical thrombectomy up to ~24 hours in selected patients. Last-known-well time is the single most important fact for treatment decisions.

Physiology. The ischemic penumbra (threatened but salvageable brain) shrinks each minute; faster reperfusion saves more neurons and improves outcomes.

Safety. Hold aspirin and oral intake until imaging excludes hemorrhage and dysphagia is assessed; activate the stroke pathway first.

Memory aids

• F = Face drooping
• A = Arm weakness
• S = Speech difficulty
• T = Time to call emergency services

Quick review

• F = Face drooping — Contralateral facial weakness
• A = Arm weakness — Contralateral motor deficit
• S = Speech difficulty — Dysarthria or aphasia
• T = Time to call emergency services — Time is brain / last-known-well