Cincinnati Prehospital Stroke Scale¶
Category: Concepts Sources: raw/protocols/nm-sop-guidelines-treatment-2022.pdf Last updated: 2026-04-05
Overview¶
The Cincinnati Prehospital Stroke Scale (CPSS) is a three-component screening tool for suspected stroke. It evaluates facial droop, arm drift, and speech abnormality. Any one of the three components being abnormal constitutes a positive screen — the patient should be treated as a possible stroke until proven otherwise.
CPSS is fast (60–90 seconds), requires no equipment, and can be performed on a patient found anywhere — on the floor, in a chair, in a bed. It is the standard prehospital stroke screening tool in NM and one of the most tested topics on the NREMT cognitive exam.
The goal of the Cincinnati screen is not to diagnose stroke — the goal is to identify patients who need rapid transport to a Stroke Center and early hospital activation. CPSS gets you there. See stroke for full clinical management.
The Three Components¶
1. Facial Droop¶
How to test: Ask the patient to smile or show their teeth.
Normal: Both sides of the face move symmetrically. Both corners of the mouth elevate equally.
Abnormal: One side of the face droops or does not move. Asymmetrical facial movement.
What it indicates: Unilateral facial weakness suggests motor cortex or corticobulbar tract involvement — the upper motor neuron pathway that controls voluntary facial movement. The CN VII (facial nerve) controls facial muscles; in a central (brain) lesion, the upper face is partially spared (bilateral cortical control to the upper face) but the lower face on the contralateral side to the lesion droops.
Field tip: Some patients with dentures or facial injuries may appear to have asymmetry. Ask "Does your face normally move like this?" or compare to a photo ID. Baseline asymmetry is not a new stroke finding.
Peripheral vs. central droop: A peripheral CN VII lesion (Bell's palsy) causes unilateral weakness of the entire face including the forehead/eyebrow. A central stroke lesion typically spares the forehead — the patient can still wrinkle their forehead on the affected side. This distinction is made in the hospital, not prehospital — if you see any new facial asymmetry, treat as stroke.
2. Arm Drift¶
How to test: Ask the patient to extend both arms in front of them, palms up, with eyes closed. Hold for 10 seconds. Watch for drift.
Normal: Both arms remain level and stationary for the full 10 seconds.
Abnormal: One arm drifts downward (or inward), or one arm has no movement at all (hemiplegia).
What it indicates: Arm drift indicates contralateral motor cortex or corticospinal tract weakness. The pyramidal motor system crosses (decussates) in the brainstem — a left hemispheric stroke causes right-sided weakness. Gravity acting on a weak arm causes progressive downward drift.
Why eyes closed: Removing visual feedback isolates the motor and proprioceptive systems. A patient can sometimes hold a weak arm up temporarily by watching it — removing vision reveals the deficit.
Grading: Partial drift (arm moves down but doesn't fall completely) is still abnormal. A completely falling arm is severe motor deficit. Any drift = abnormal.
Subtle drift: Some patients with early or minor stroke have very slight drift. Hold the full 10 seconds. A brief observation will miss subtle findings.
3. Speech Abnormality¶
How to test: Ask the patient to repeat a phrase. Commonly used: "You can't teach an old dog new tricks" or "The sky is blue in Cincinnati."
Normal: Patient repeats the phrase clearly and correctly, without slurring, wrong words, or inability to speak.
Abnormal: Three possible presentations: - Slurred speech (dysarthria): Words are muffled, slurred, or unclear — the motor system for articulation is impaired. - Wrong words / aphasia: Patient says the wrong words or substitutes nonsense words for correct words — the language center (Broca's or Wernicke's area in the dominant hemisphere) is involved. - Mute: Patient cannot produce speech at all — severe expressive aphasia or global aphasia.
What it indicates: Dysarthria localizes to motor pathways for speech production (can originate from many locations). Aphasia (wrong words, word substitution, inability to speak) localizes to the dominant cerebral hemisphere (usually left). Wernicke's aphasia: patient produces fluent but nonsensical speech. Broca's aphasia: patient speaks haltingly with good comprehension but limited output.
Important distinction: Slurred speech in an intoxicated patient may mimic dysarthria. Always check blood glucose — hypoglycemia can cause both slurred speech and confusion. See diabetic-emergencies.
Interpreting the Screen¶
One or more abnormal findings = positive Cincinnati screen = possible stroke.
Published sensitivity with 1 abnormal finding is approximately 59–72% (sensitivity varies by subtype of stroke). Specificity is lower — many conditions can mimic stroke. However, in the prehospital setting, false positives are acceptable: a stroke mimic transported urgently to a Stroke Center is far better than a stroke missed and transported to a non-capable facility.
| Findings | Interpretation |
|---|---|
| All three normal | Negative screen; stroke less likely but not excluded |
| 1 of 3 abnormal | Positive screen — possible stroke; treat as stroke |
| 2 of 3 abnormal | Strong positive — high probability of stroke |
| All 3 abnormal | Very high probability of stroke or large vessel occlusion (LVO) |
Limitation: CPSS with all three components abnormal carries higher sensitivity for LVO (large vessel occlusion) stroke, which may benefit from mechanical thrombectomy. NM protocol directs use of LVO-specific scales (RACE, C-STAT, LAMS) in addition to CPSS to identify thrombectomy candidates.
FAST Mnemonic¶
FAST is a public health mnemonic (designed for layperson recognition) that covers the same core components:
| FAST | Component | Cincinnati Equivalent |
|---|---|---|
| F — Face | Facial drooping | Facial droop |
| A — Arms | Arm weakness | Arm drift |
| S — Speech | Speech difficulty | Speech abnormality |
| T — Time | Call 911 immediately | Transport with advance notification |
FAST and Cincinnati test the same three clinical findings. Cincinnati provides more specific testing protocols (how to test each component, what counts as abnormal). FAST is for bystanders. CPSS is the provider tool.
Last Known Well — The Critical History Element¶
"Last known well" is the single most important piece of history information for a stroke patient. It is the last time the patient was observed at their neurological baseline.
This is not the same as symptom onset time: - A patient may have gone to sleep normal and woken up with a facial droop. The last known well time is when they went to sleep — not when they woke up. - A patient who had a stroke while alone, discovered by family hours later — the last known well is when the family last saw them normal.
Why it matters: The time window for IV tPA (tissue plasminogen activator — the clot-dissolving drug for ischemic stroke) is approximately 3–4.5 hours from last known well, not from when the patient was found. If last known well is unknown, the patient may not be a tPA candidate — which is a worse outcome than a known 3-hour window.
Mechanical thrombectomy (catheter-based clot removal for LVO strokes) has a wider time window — up to 24 hours from last known well in selected patients. Early identification of LVO (via scales) and rapid transport to a thrombectomy-capable center can benefit these patients even with delayed presentation.
How to get the time: Question every bystander, family member, and neighbor. "When was the last time you saw him and he seemed normal?" Look for phone or text message activity logs (last time he sent a text = last known interaction). If the patient has a smartwatch with vitals, time-stamped HR data may help narrow the window.
Transport Decision¶
Positive Cincinnati screen = priority transport to Stroke Center with advance notification.
Do not delay on scene. The time-sensitive interventions (tPA, thrombectomy) are hospital-only. The EMT-B's job is early recognition, early transport, and early notification — not further diagnostics.
Advance notification contents: - Positive stroke screen (which finding was abnormal) - Last known well time (or "unknown last known well") - Current vital signs and LOC - BGL result - Blood thinner use (anticoagulants — warfarin, Xarelto, Eliquis, Pradaxa — affects tPA eligibility) - ETA
Do NOT: - Treat hypertension prehospital in suspected stroke — elevated BP may be compensatory - Give aspirin for suspected stroke — hemorrhagic stroke (15% of strokes) contraindicates anticoagulants - Delay transport for additional on-scene assessment
Check BGL: Hypoglycemia is the most common stroke mimic. BGL <60 mg/dL with neurological findings → treat hypoglycemia first. If neurological findings resolve with glucose treatment → hypoglycemia was the cause. If they do not fully resolve → treat as stroke.
Sensitivity and Specificity¶
| Metric | CPSS Value |
|---|---|
| Sensitivity (any 1 finding) | ~59–72% for all stroke |
| Sensitivity (all 3 findings) | ~66% for LVO stroke |
| Specificity | ~90–97% (high specificity = few false positives) |
High specificity means: if the Cincinnati screen is positive, it is usually a stroke or a serious neurological condition. Low sensitivity means: a negative Cincinnati screen does not rule out stroke — posterior circulation strokes (vertebrobasilar) may present with dizziness, ataxia, and diplopia without classic CPSS findings.
A patient with sudden onset vertigo, double vision, and severe headache with a negative Cincinnati screen still warrants urgent transport.
Common Mistakes¶
- Testing arm drift with eyes open — The whole point of closing the eyes is to remove visual compensation. An arm held up by watching it does not reflect true motor deficit.
- Not holding the arm drift test for a full 10 seconds — Subtle drift only appears at 7–10 seconds. Brief checks miss early deficits.
- Asking a leading question for facial droop — "Does your face look normal?" primes the patient. Ask them to smile or show teeth and observe.
- Confusing baseline asymmetry with new droop — Some patients have asymmetric smiles normally. Compare to ID photo or ask family.
- Skipping blood glucose — Hypoglycemia is the most important stroke mimic. BGL check is mandatory before or during transport for any altered LOC or focal neurological findings.
- Using symptom onset instead of last known well — These are different. A patient who woke up with a stroke at 6 AM had their last known well the night before. Transport destination and tPA eligibility depend on the correct time.
- Giving aspirin "just in case" — Hemorrhagic stroke contraindicates aspirin. No aspirin for suspected stroke.
NM Protocol Notes¶
From NM EMS Treatment Guidelines (2022):
- Perform serial prehospital stroke assessments: Cincinnati, Los Angeles Motor Scale, or FAST
- Also perform LVO scale: RACE (Rapid Arterial oCclusion Evaluation), C-STAT, or LAMS
- Establish last known well time, last seen at baseline, BGL
- Document blood thinner use
- Transport to nearest Stroke Center or acute stroke-ready hospital with early notification
- Do NOT treat hypertension prehospital
- ALS intercept or aeromedical transport may be appropriate for symptomatic stroke, particularly in San Juan County's rural corridors
NREMT Relevance¶
One of the most consistently tested topics on the cognitive exam:
- Know all three CPSS components and how to test each
- Know that any 1 of 3 abnormal = positive screen = possible stroke
- Know that "last known well" is NOT the same as "when symptoms were noticed"
- Know: NO aspirin for stroke (hemorrhagic contraindication)
- Know: NO hypertension treatment prehospital for stroke
- Know: Check BGL — hypoglycemia mimics stroke, is the most important mimic
- Know: FAST components and how they map to Cincinnati
- Know: Transport to Stroke Center with advance notification; do not delay on scene
Related¶
- stroke — clinical management, transport decisions, protocol details
- glasgow-coma-scale — neurological assessment complement to stroke screening
- avpu — LOC assessment in stroke patients; low LOC = priority transport
- sample-opqrst — last known well is captured in OPQRST-T; blood thinners in SAMPLE-M
- diabetic-emergencies — hypoglycemia as stroke mimic; must check BGL on every apparent stroke
Sources¶
raw/protocols/nm-sop-guidelines-treatment-2022.pdf— Suspected Stroke/TIA protocol (p. 45)