NIHSS in Acute Stroke: From Score to Treatment Decision in Under 10 Minutes
Dr. Priya Sharma
Consultant Neurologist
Time is brain. The NIHSS is your fastest path from clinical assessment to thrombolysis eligibility. Master the 15-item scale, understand the scoring pitfalls, and know exactly which scores unlock which treatments.
Why NIHSS Matters
Every 1 minute of untreated ischaemic stroke results in the death of approximately 1.9 million neurons. The NIHSS is the validated tool that quantifies stroke severity, guides treatment eligibility, and predicts outcomes — all in under 10 minutes.
The 15 Items
The NIHSS assesses:
- →Level of consciousness (0–3)
- →LOC questions (0–2)
- →LOC commands (0–2)
- →Best gaze (0–2)
- →Visual fields (0–3)
- →Facial palsy (0–3)
- →Motor arm — left (0–4)
- →Motor arm — right (0–4)
- →Motor leg — left (0–4)
- →Motor leg — right (0–4)
- →Limb ataxia (0–2)
- →Sensory (0–2)
- →Best language (0–3)
- →Dysarthria (0–2)
- →Extinction/inattention (0–2)
Score Interpretation
| NIHSS | Severity | Clinical Implication |
|---|
| 0 | No stroke | — |
| 1–4 | Minor | Dual antiplatelet (POINT/CHANCE) |
| 5–15 | Moderate | IV tPA if eligible |
| 16–20 | Moderate-severe | IV tPA + consider thrombectomy |
| 21–42 | Severe | Thrombectomy evaluation |
tPA Eligibility
IV alteplase is indicated for NIHSS ≥ 3 (lower scores may still be treated if deficit is disabling) within 4.5 hours of last known well.
Key exclusions:
- •NIHSS > 25 (relative contraindication — high haemorrhage risk)
- •Rapidly improving symptoms
- •Blood glucose < 50 or > 400 mg/dL
- •Recent major surgery (< 14 days)
- •Anticoagulation with INR > 1.7
Mechanical Thrombectomy
For large vessel occlusion (LVO) confirmed on CTA:
- •NIHSS ≥ 6 within 24 hours (DAWN/DEFUSE-3 criteria with perfusion imaging)
- •No upper NIHSS limit for thrombectomy
- •Anterior circulation: ICA, M1, M2 segments
- •Posterior circulation: basilar artery occlusion
Common Scoring Pitfalls
Posterior circulation strokes are notoriously underscored by NIHSS. A patient with basilar artery occlusion may have NIHSS 4–6 but be critically ill. Always correlate with imaging. Aphasia vs. dysarthria: Aphasia (item 9) reflects language processing; dysarthria (item 14) reflects articulation. Score both independently. Ataxia: Only score if not explained by weakness. If the patient has arm weakness, ataxia in that arm scores 0.Serial NIHSS
A decrease of ≥ 4 points = clinically meaningful improvement.
An increase of ≥ 4 points = neurological deterioration → urgent re-evaluation, repeat CT head.
Clinical Disclaimer
This article is intended for educational purposes and clinical decision support only. Always correlate with the individual patient's clinical context, institutional guidelines, and current evidence. ClinicalCalc Pro does not replace clinical judgment.
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