Stroke assessment starts with recognizing a small set of physical signs that point to interrupted blood flow in the brain. The most widely used tool is the BE-FAST checklist, which covers six categories and takes less than a minute to perform. Speed matters more than precision here: clot-dissolving treatment is most effective within 4.5 hours of symptom onset, and every minute of delay costs brain tissue.
The BE-FAST Checklist
BE-FAST expanded the older FAST acronym by adding two categories that were causing strokes to be missed. Each letter represents a specific sign to check:
- Balance: Sudden difficulty walking, loss of coordination, or leg weakness on one side.
- Eyes: Vision loss in one or both eyes, double vision, or sudden blurring.
- Face: One side of the face droops when the person tries to smile. Ask them to show their teeth.
- Arm: One arm drifts downward when both arms are raised with eyes closed. This also applies to grip strength differences between hands.
- Speech: Slurred words, garbled sentences, or inability to repeat a simple phrase like “the sky is blue.”
- Time: Note the exact time symptoms started and call emergency services immediately.
The original FAST version caught most strokes but missed those affecting the back of the brain, which often cause balance and vision problems rather than obvious arm weakness or facial drooping. Adding the B and E categories closes that gap significantly.
Symptoms That Don’t Fit the Usual Pattern
Not every stroke announces itself with a drooping face and a weak arm. Strokes in the posterior circulation, the blood vessels supplying the brainstem and cerebellum, often look nothing like the textbook description. The most common symptom is sudden, severe vertigo or dizziness. Fewer than 20% of these patients have obvious neurological signs like limb weakness, and they can score a zero on formal stroke scales, making them easy to miss.
This matters because isolated vertigo is actually the most common warning symptom before a full posterior circulation stroke, yet it is rarely recognized as vascular at the first medical contact. Emergency physicians sometimes mistake it for an inner ear problem, but strokes in certain brainstem locations frequently cause true spinning vertigo, and some even produce tinnitus or hearing loss, symptoms that further mimic ear disorders.
Young adults face a particular risk of misdiagnosis. Patients aged 18 to 44 who are having a stroke are seven times more likely to be misdiagnosed than patients over 75. One reason is that a tear in the vertebral artery, a known stroke cause in younger people, closely mimics a severe migraine.
Atypical Symptoms in Women
Women are more likely than men to present with “generalized” stroke symptoms that aren’t obviously tied to one part of the brain. These include sudden confusion, fatigue, general weakness, headache, altered mental state, or loss of consciousness. Women still get the classic signs too, but the additional nonspecific symptoms can delay recognition, especially if the person or those around them attribute the symptoms to something else.
What Happens at the Hospital
Once emergency responders suspect a stroke, the priority is brain imaging. A non-contrast CT scan is typically performed first because it’s fast and reliably detects bleeding in the brain, which determines whether clot-dissolving medication is safe to give. The median time from arrival to imaging is about 27 minutes in most stroke centers, though hospitals aiming for best practice push for faster.
MRI with diffusion-weighted sequences is more sensitive for detecting the actual area of damaged tissue, and hospitals that have shifted to an MRI-first approach cut the rate of non-stroke patients mistakenly receiving clot-dissolving drugs roughly in half (4.3% vs. 8.6% with CT-first). The tradeoff is minimal: MRI adds only about two extra minutes to the imaging timeline for patients who arrive early enough for treatment.
Medical teams also use the NIH Stroke Scale, a structured exam that scores 11 categories including consciousness, eye movement, visual fields, facial movement, limb strength, coordination, sensation, language, and speech clarity. Each category gets a numerical score, and the total determines severity. A person who is alert and responsive scores zero on the consciousness item, while someone who requires painful stimulation to respond scores a two or three. The full scale guides treatment decisions and helps predict recovery.
The Treatment Window
For ischemic strokes (caused by a clot rather than bleeding), intravenous clot-dissolving medication is the standard treatment for eligible patients within 4.5 hours of symptom onset or the last time the person was known to be well. That 4.5-hour window has been the established cutoff, but recent clinical trials have tested treatment out to 9 hours and even 24 hours in selected patients who have salvageable brain tissue visible on advanced imaging. These extended windows use specific imaging criteria to confirm that enough tissue can still be rescued to justify the treatment’s bleeding risk.
For strokes caused by a blockage in a large brain artery, mechanical clot retrieval is an option that can extend the treatment window further. Emergency responders increasingly use rapid motor assessments in the field to identify these large vessel blockages before the patient reaches the hospital. One such tool, the Los Angeles Motor Scale, uses three motor checks scored on a 10-point scale. A score of 4 or higher predicts a large vessel blockage with good accuracy, allowing paramedics to route the patient directly to a hospital equipped for clot retrieval rather than a closer facility that may not offer it.
Stroke vs. Transient Ischemic Attack
A transient ischemic attack, or TIA, produces the same symptoms as a stroke but resolves on its own, typically within an hour. The older definition used a 24-hour cutoff, but that has been replaced. The current definition requires that imaging show no evidence of permanent brain tissue damage. If imaging reveals damage, it’s classified as a stroke regardless of whether symptoms improved.
A TIA is not a minor event. It is a warning that a full stroke may follow, sometimes within days. The assessment process is the same: anyone experiencing sudden neurological symptoms should be evaluated urgently, even if those symptoms have already resolved by the time help arrives. The underlying cause, whether a narrowed artery, a heart rhythm problem, or a clot, still needs to be identified and treated.
How to Check Someone Right Now
If you’re with someone and suspect a stroke, run through three quick checks. Ask them to smile and watch for one side of the face lagging. Ask them to raise both arms and hold them up with eyes closed for 10 seconds, watching for one arm drifting down. Ask them to repeat a simple sentence and listen for slurring or word-finding trouble. Any single failure is enough to call emergency services.
Note the time you first noticed something wrong. If the person woke up with symptoms, the “last known well” time is when they went to sleep or were last seen acting normally. This timestamp directly determines which treatments are available. Do not drive the person to the hospital yourself unless there is no ambulance available. Paramedics can begin assessment en route and alert the receiving hospital to prepare, which saves critical minutes once the patient arrives.