The National Institutes of Health Stroke Scale is a tool used by doctors to measure the level of patients' impairment due to strokes, states About.com. The scale measures level of impairments scored from between 0 and 42.
The NIH Stroke Scale measures the impairment levels of consciousness, vision, sensation, movement, speech and language, notes About.com. People with scores of zero did not have a stroke, while those with scores between one and four suffered a minor stroke. Scores between five and 15 indicate a moderate stroke, while scores between 15 and 20 indicate a moderate to severe stroke. People with scores between 21 and 42 on the NIH Stroke Scale have suffered a severe stroke.