NIH Stroke Scale (NIHSS) Calculator

inputs

1a. Level of consciousness

1b. LOC questions (month + age)

1c. LOC commands (close/open eyes, grip/release hand)

2. Best gaze (horizontal eye movements)

3. Visual fields

4. Facial palsy

5a. Motor arm — left (hold at 90° sitting / 45° supine for 10 seconds)

5b. Motor arm — right

6a. Motor leg — left (hold at 30° supine for 5 seconds)

6b. Motor leg — right

7. Limb ataxia (finger-nose, heel-shin)

8. Sensory

9. Best language

10. Dysarthria

11. Extinction/inattention (neglect)

✓ when to use

Perform on all patients presenting with suspected acute stroke. NIHSS is essential for: determining thrombolysis eligibility, identifying large vessel occlusion candidates for thrombectomy, documenting severity for serial monitoring, and communicating between clinical teams. Should be performed at baseline, post-thrombolysis, at 24 hours, and at discharge.

✗ when not to use

NIHSS underestimates posterior circulation strokes (brainstem and cerebellar findings are poorly captured). It overweights left hemisphere function (language items contribute more points). A low NIHSS does not exclude significant stroke — a pure motor lacunar stroke may score 3–4 yet cause significant disability. NIHSS certification/training is recommended for reliable administration.

clinical pearls

NIHSS certification is important. Trained assessors have significantly better inter-rater reliability. Free online certification is available at nihstrokescale.org.
NIHSS has a left-hemisphere bias — aphasia (item 9) can score up to 3, while neglect (item 11, more common in right hemisphere strokes) scores maximum 2. Right hemisphere strokes are systematically underscored.
An NIHSS ≥6 with anterior circulation symptoms has a high positive predictive value for large vessel occlusion (LVO). However, lower NIHSS does not exclude LVO — always consider CT angiography if LVO is suspected.
Serial NIHSS monitoring is critical. A ≥4-point increase from baseline suggests clinical deterioration (haemorrhagic transformation, re-occlusion, oedema) and warrants urgent re-imaging.
For thrombolysis decision-making, focus on whether the deficit is 'disabling' rather than the absolute NIHSS score. An isolated hand weakness (NIHSS 1–2) in a surgeon is disabling; an NIHSS 3 with mild facial droop and dysarthria may not be.

✓ when to use

✗ when not to use

clinical pearls

NIHSS certification is important. Trained assessors have significantly better inter-rater reliability. Free online certification is available at nihstrokescale.org.
NIHSS has a left-hemisphere bias — aphasia (item 9) can score up to 3, while neglect (item 11, more common in right hemisphere strokes) scores maximum 2. Right hemisphere strokes are systematically underscored.
An NIHSS ≥6 with anterior circulation symptoms has a high positive predictive value for large vessel occlusion (LVO). However, lower NIHSS does not exclude LVO — always consider CT angiography if LVO is suspected.
Serial NIHSS monitoring is critical. A ≥4-point increase from baseline suggests clinical deterioration (haemorrhagic transformation, re-occlusion, oedema) and warrants urgent re-imaging.
For thrombolysis decision-making, focus on whether the deficit is 'disabling' rather than the absolute NIHSS score. An isolated hand weakness (NIHSS 1–2) in a surgeon is disabling; an NIHSS 3 with mild facial droop and dysarthria may not be.

NIH Stroke Scale (NIHSS)

inputs

✓ when to use

✗ when not to use

clinical pearls

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