NIHSS calculator

Quantifies stroke severity across 15 items to a total out of 42, and sets the threshold for considering thrombectomy.

What it is used for

The National Institutes of Health Stroke Scale is the standard measure of neurological deficit in acute stroke. Fifteen items are scored and summed to a maximum of 42, giving a reproducible severity figure that guides reperfusion decisions and lets change be tracked between assessments. In the UK, NICE NG128 uses an NIHSS of 6 or more as the point at which thrombectomy is considered where a large vessel occlusion is confirmed on CT angiography. Thrombolysis is a separate decision governed by the 4.5-hour window and its own contraindications.

The 15 scored items

The full version in the app includes the official stimulus cards — the description picture, naming sheet, reading sentences and dysarthria word list — so items 9 and 10 can be scored properly at the bedside.

How the score is interpreted

When not to use it

• The NIHSS under-weights posterior circulation strokes, which can be disabling at a low score.
• It is a severity measure, not a diagnosis — imaging is required before any antiplatelet or thrombolysis decision.
• Scoring drifts between assessors without training; score the items as written rather than by overall impression.