The National Institute of Health (NIH) stroke scale (NIHSS) is a standardized method used by physicians and other health care professionals to measure the level of impairment caused by a stroke.
The NIH stroke scale serves several purposes, but its main use in clinical medicine is during the assessment of whether or not the degree of disability caused by a given stroke merits treatment with tPA. Another important use of the NIHSS is in research, where it allows for the objective comparison of efficacy across different stroke treatments and rehabilitation interventions.
The NIH stroke scale measures several aspects of brain function, including consciousness, vision, sensation, movement, speech, and language. A certain number of points are given for each impairment uncovered during a focused neurological examination. A maximal score of 42 represents the most severe and devastating stroke. Current guidelines as of 2008 allow strokes with scores greater than 4 points to be treated with tPA.
The level of stroke severity as measured by the NIH stroke scale scoring system:
- 0= no stroke
- 1-4= minor stroke
- 5-15= moderate stroke
- 15-20= moderate/severe stroke
- 21-42= severe stroke
Source:
Bradley G Walter, Daroff B Robert, Fenichel M Gerald, Jancovic, Joseph; Neurology in clinical practice, principles of diagnosis and management. Philadelphia Elsevier, 2004.

