What is the NIHSS?
The NIH Stroke Scale is the standard tool for quantifying neurological deficit after acute stroke, scoring 15 domains from level of consciousness through language and inattention. It grew out of earlier work by Brott and colleagues, published in Stroke in 1989, and became central to acute stroke trials and treatment-eligibility decisions (alongside time-window and imaging criteria) from the 1990s onward.
How to calculate the NIHSS
Each of the 15 items is scored independently using its own defined scale (shown above), and the total is the sum across all items - ranging from 0 (no deficit) to 42 (maximum deficit). The breakdown by domain matters as much as the total, since it shows which neurological systems are affected.
Some items have an "untestable" option (e.g. prior amputation, joint fusion, or intubation preventing assessment) - these are recorded separately per the official NIHSS instructions rather than forced into the standard numeric scale, since this affects how the total should be interpreted.
Interpretation
| Score | Severity |
|---|---|
| 0 | No stroke symptoms |
| 1–4 | Minor stroke |
| 5–15 | Moderate stroke |
| 16–20 | Moderate-to-severe stroke |
| 21–42 | Severe stroke |
Important note
Reliable clinical use of the NIHSS requires formal training and certification - this calculator is a learning aid for understanding the scale's structure and scoring, not a substitute for certified bedside assessment in real patient care.
References
Brott T, Adams HP Jr, Olinger CP, et al. Measurements of acute cerebral infarction: a clinical examination scale. Stroke. 1989.
See also: Cranial Nerves OSCE Guide.