NIH Stroke Scale Calculator (NIHSS total score)

Understanding the NIH Stroke Scale calculator — concept and principle

The National Institutes of Health Stroke Scale (NIHSS) scores a standard neurological examination to measure how severe a stroke is. Emergency and stroke teams use it on arrival and repeatedly afterwards to guide treatment decisions, track change and communicate clearly.

How it is calculated

NIHSS total (0–42) = sum of 15 items scored in a fixed order:

• 1a–1c consciousness, questions and commands
• 2 gaze, 3 visual fields, 4 facial palsy
• 5a, 5b arms and 6a, 6b legs (0 = no drift … 4 = no movement)
• 7 limb ataxia, 8 sensation, 9 language, 10 dysarthria, 11 extinction and inattention (neglect)

Limbs that cannot be tested (amputation, joint fusion) are marked untestable and add 0 here. The calculator also shows the consciousness and motor subtotals.

The principle

Each item tests a function supplied by particular brain areas, so the pattern reflects where the stroke is and the total reflects how much brain is affected. Scores are based on what the patient actually does on the first attempt, without coaching, which keeps results consistent between examiners. Higher scores mean larger deficits. Left-hemisphere strokes may score higher than right-hemisphere strokes of similar size because language items carry more points than neglect.

Worked example

Default inputs: alert and correct (1a–1c 0), partial gaze palsy 1, no field loss 0, partial facial palsy 2, left arm 0, right arm 2, left leg 0, right leg 1, ataxia 0, sensory loss 1, aphasia 1, dysarthria 1, no neglect 0.

1. Consciousness items = 0.
2. Motor items = 0 + 2 + 0 + 1 = 3.
3. Total = 0 + 1 + 0 + 2 + 3 + 0 + 1 + 1 + 1 + 0 = 9.

How to read the result

Commonly used bands are 0 no stroke symptoms, 1–4 minor, 5–15 moderate, 16–20 moderate to severe and 21–42 severe, but there is no single official banding. A low score does not mean a stroke is harmless; isolated aphasia or vision loss can be disabling. Changes of a few points over time are clinically important.

Common mistakes

• Scoring what the patient could do rather than what they did.
• Coaching or repeating instructions.
• Adding points for untestable limbs.

Frequently asked questions

Who can perform the NIHSS?

Doctors, nurses and paramedics, ideally after official training and certification.

Does a high score rule out treatment?

No. Treatment decisions use many factors, including imaging and time since onset.

How long does it take?

About 5–10 minutes for a trained examiner.

Sources: National Institute of Neurological Disorders and Stroke (NINDS), NIH Stroke Scale · Brott T, Adams HP Jr, Olinger CP, et al., "Measurements of acute cerebral infarction: a clinical examination scale", Stroke 1989;20(7):864–870