NIHSS Stroke Severity Guide
| NIHSS Score | Severity | Typical Deficits | Outcome (90-day mRS 0–2) |
|---|---|---|---|
| 0 | No stroke symptoms | Normal examination | ~95% |
| 1–4 | Minor stroke | Subtle findings — sensory, mild motor, mild speech | ~80–90% |
| 5–15 | Moderate stroke | Clear motor/speech deficits, partial limb weakness | ~30–60% |
| 16–20 | Moderate–Severe | Dense hemiplegia, global aphasia, gaze deviation | ~10–25% |
| 21–42 | Severe stroke | Coma, severe neurological impairment | <10% |
tPA (Alteplase) in Acute Ischaemic Stroke
Intravenous alteplase (0.9 mg/kg, max 90 mg) remains the standard pharmacological reperfusion therapy for eligible patients with acute ischaemic stroke. Key eligibility criteria per AHA/ASA 2019 guidelines:
- Age ≥18 years; symptom onset within 3 hours (extended to 4.5 hours in selected patients per ECASS-3 criteria)
- NIHSS ≥4 (relative — low NIHSS may still benefit; high NIHSS may still be treated)
- CT head showing no haemorrhage or established large infarct (>1/3 MCA territory)
- No absolute contraindications: no prior ICH, intracranial neoplasm/AVM, active internal bleeding, recent (<3 months) head trauma/brain surgery, BP >185/110 despite treatment
Mechanical Thrombectomy Eligibility
Mechanical thrombectomy (MT) has transformed outcomes for large vessel occlusion (LVO) strokes. AHA/ASA 2018 extended MT window criteria: NIHSS ≥6, pre-stroke mRS ≤1, ASPECTS ≥6 on CT, confirmed LVO on CTA, treatment within 6 hours of onset (up to 24 hours in selected wake-up/late-window cases with favourable CT perfusion or DWI-FLAIR mismatch on MRI). NIHSS score does not independently exclude patients from MT consideration — LVO must be confirmed on vascular imaging.
NIHSS as a Serial Monitoring Tool
A reduction in NIHSS of ≥4 points from baseline is the standard definition of neurological improvement used in clinical trials (including NINDS trial). NIHSS should be performed: at baseline (admission), at 2 hours, 24 hours, 7 days, and at discharge. A worsening NIHSS of ≥4 points from baseline suggests haemorrhagic transformation, cerebral oedema, or re-occlusion — requiring urgent CT head and neurology review.