The NIH Stroke Scale (NIHSS) was developed by the National Institute of Neurological Disorders and Stroke to provide a standardised, reproducible assessment of neurological deficit severity in acute stroke patients. Originally published in 1989, it has become the global standard for stroke severity quantification, used in clinical trials, treatment eligibility determinations (particularly for IV thrombolysis and mechanical thrombectomy), and outcome prediction. The scale consists of 15 items assessing consciousness, gaze, visual fields, facial palsy, limb motor function, ataxia, sensation, language, dysarthria, and extinction.
The NIH Stroke Scale (NIHSS) was developed by the National Institute of Neurological Disorders and Stroke to provide a standardised, reproducible assessment of neurological deficit severity in acute stroke patients. Originally published in 1989, it has become the global standard for stroke severity quantification, used in clinical trials, treatment eligibility determinations (particularly for IV thrombolysis and mechanical thrombectomy), and outcome prediction. The scale consists of 15 items assessing consciousness, gaze, visual fields, facial palsy, limb motor function, ataxia, sensation, language, dysarthria, and extinction.
Validated In
Validated in multiple large stroke trials including NINDS tPA trial, ECASS, SITS-MOST
Thomas Brott, Harold P. Adams Jr., and colleagues at the University of Cincinnati
1a. Level of Consciousness
0=Alert, 1=Drowsy, 2=Obtunded, 3=Unresponsive
1b. LOC Questions (month/age)
0=Both correct, 1=One correct, 2=Neither correct
1c. LOC Commands (open/close eyes, fist)
0=Both obeyed, 1=One obeyed, 2=Neither obeyed
2. Best Gaze
0=Normal, 1=Partial palsy, 2=Forced deviation
3. Visual Fields
0=No loss, 1=Partial hemianopia, 2=Complete, 3=Bilateral
4. Facial Palsy
0=Normal, 1=Minor, 2=Partial, 3=Complete
5-6. Motor Arm/Leg (each side)
0=No drift to 4=No movement (0-4 per limb)
7. Limb Ataxia
0=Absent, 1=One limb, 2=Two limbs
8. Sensory
0=Normal, 1=Mild/moderate loss, 2=Severe/total loss
9. Best Language
0=No aphasia, 1=Mild/moderate, 2=Severe, 3=Mute/global
10. Dysarthria
0=Normal, 1=Mild/moderate, 2=Severe/unintelligible
11. Extinction/Inattention
0=Normal, 1=Inattention one modality, 2=Profound
NIHSS ≤5 correlates with minor stroke — these patients have excellent prognosis and may be candidates for dual antiplatelet therapy instead of IV tPA (POINT/CHANCE trials).
NIHSS ≥6 with confirmed large vessel occlusion (LVO) on CTA: mechanical thrombectomy reduces disability even up to 24 hours post-onset if perfusion imaging demonstrates salvageable tissue (DAWN/DEFUSE-3 criteria).
A "wake-up stroke" or unknown onset time does not preclude treatment — use MRI DWI/FLAIR mismatch or CT perfusion to identify the therapeutic window.
The score is poorly sensitive for posterior circulation strokes (brainstem/cerebellum) which may have severe deficits with low NIHSS scores.
Serial NIHSS monitoring: a decrease of ≥4 points = clinically meaningful improvement; increase of ≥4 = neurological deterioration requiring urgent re-evaluation.
tPA eligibility requires NIHSS ≥3 (lower scores may still be treated if disabling deficit) within 4.5 hours of last known well.
Brott T, et al. Measurements of Acute Cerebral Infarction: A Clinical Examination Scale. Stroke. 1989;20(7):864-870.
Adams HP Jr, et al. Baseline NIH Stroke Scale Score Strongly Predicts Outcome After Stroke. Neurology. 1999;53(1):126-131.
Powers WJ, et al. Guidelines for the Early Management of Patients With Acute Ischemic Stroke: 2019 Update to the 2018 AHA/ASA Guidelines. Stroke. 2019;50(12):e344-e418.