The Cincinnati Prehospital Stroke Scale (CPSS) is a three-part physical assessment designed to identify strokes quickly outside of a hospital. It checks for facial droop, arm weakness, and speech problems, and it takes less than a minute to perform. Paramedics, emergency responders, and even bystanders can use it to decide whether someone needs emergency stroke treatment.
The Three Tests
Each part of the scale targets a different function that strokes commonly disrupt. The person administering the test asks the patient to do three things, then watches for abnormalities.
Facial droop: The patient is asked to smile. Normally, both sides of the face move equally. If one side doesn’t move or droops noticeably compared to the other, that counts as abnormal. This asymmetry reflects damage to the brain areas controlling facial muscles on one side of the body.
Arm weakness: The patient is asked to close their eyes and hold both arms straight out in front of them for 10 seconds. Both arms should stay level. If one arm drifts downward or can’t be raised at all, that’s a positive finding. This is sometimes called “arm drift” and indicates that motor control on one side has been compromised.
Speech: The patient is asked to repeat a simple phrase, such as “The early bird catches the worm.” The evaluator listens for slurred words, garbled sounds, or an inability to speak at all. Any of these counts as abnormal. Some people can form words clearly but use the wrong ones or can’t find words, which also signals a problem.
What the Results Mean
The scale doesn’t produce a numerical score the way some clinical tools do. Instead, each of the three tests is graded as either normal or abnormal. If even one of the three is abnormal, the likelihood of a stroke increases significantly, and the person should be transported to a hospital immediately.
A 2024 systematic review and meta-analysis found that when any one or more of the three signs was present, the CPSS had a sensitivity of 97%, meaning it correctly flagged nearly all stroke patients. The tradeoff was low specificity at that threshold (17%), meaning it also flagged many people who weren’t having a stroke. When two or more signs were abnormal, sensitivity dropped to 82% but specificity rose to 62%. With all three signs abnormal, sensitivity was 60% and specificity reached 81%. In practical terms, more abnormal signs make a stroke diagnosis more certain, but even a single abnormal finding warrants emergency action because missing a stroke has far worse consequences than a false alarm.
Why Speed Matters
The CPSS was designed specifically for use before a patient reaches the hospital. Stroke treatments, particularly clot-dissolving therapy, work best when given within a narrow time window. Every minute of reduced blood flow to the brain destroys more tissue. A tool that takes under 60 seconds and requires no equipment lets first responders make faster decisions about where to transport a patient, potentially routing them directly to a hospital equipped for stroke care rather than the nearest emergency room.
How It Compares to FAST
You’ve likely seen the acronym FAST (Face, Arms, Speech, Time) used in public health campaigns. FAST and the CPSS test the same three physical signs. The only difference is that the CPSS specifies a particular sentence for the speech test, while FAST is framed as a public awareness tool with “Time” reminding people to call emergency services immediately. A large head-to-head comparison of seven prehospital stroke scales confirmed that CPSS and FAST use identical clinical items and were combined in analysis because they’re functionally the same test.
More expanded scales like BE-FAST add checks for balance problems and vision changes. These extra components help catch strokes that occur in the back of the brain (posterior strokes), which often cause dizziness, difficulty walking, or visual disturbances rather than the classic facial droop or arm weakness. The CPSS does not assess balance or vision, which is its main gap.
What the Scale Can Miss
The CPSS is excellent at catching the most common type of stroke presentation, where one side of the body loses function. But strokes affecting the brainstem or cerebellum can produce symptoms like sudden vertigo, double vision, difficulty swallowing, or loss of coordination without any facial droop, arm weakness, or speech changes. These posterior circulation strokes account for roughly 20% of all strokes and are the ones most likely to slip through the CPSS.
The scale also can’t distinguish between a stroke caused by a blood clot and one caused by bleeding in the brain. Both can produce the same outward signs. That distinction requires brain imaging at a hospital. And conditions like severe low blood sugar, seizures, or certain migraines can mimic stroke symptoms closely enough to trigger a positive result on the CPSS, which partly explains the low specificity at the one-sign threshold.
Who Uses It and When
Paramedics and EMTs are the primary users of the CPSS. It’s a standard part of emergency medical services training in many regions. But the scale was intentionally designed to be simple enough for anyone to administer. If you suspect someone is having a stroke, you can run through the three checks yourself while waiting for an ambulance: ask them to smile, raise both arms with eyes closed, and repeat a sentence. Any failure on these tests means every minute counts.
In the emergency department, physicians typically switch to more detailed scales like the NIH Stroke Scale, which evaluates 11 categories including vision, sensation, and coordination. The CPSS isn’t meant to replace that comprehensive assessment. Its value is in those first critical minutes when a quick, reliable screening can change the trajectory of someone’s outcome.