In the United States, the National Institutes of Health Stroke Scale (NIHSS) is a clinical assessment scale used to assess the probability that an individual is having a stroke, based on the patient’s clinical exam findings. It evaluates a person's ability to move, speak, see, and understand by asking questions and performing diagnostic maneuvers such as strength testing. The lower the score, the less likely a person is having a stroke. Often a patient's score is monitored periodically throughout his or her recovery period.
Elements of the NIH stroke scale evaluate a patient’s motor function, cognitive function, sensory function, level of consciousness, visual capacity, and ability to speak. In order to evaluate their overall ability to think, patients are asked simple questions such as their age or what month of the year it is. The health care professional asks the patient to move his or her extremities and face in an attempt to gauge motor capabilities. To assess speech, patients are asked to read out loud a few specified phrases.
Patients evaluated using the NIH stroke scale receive a number grade ranging from zero to 30. A normal person without any neurologic or cognitive defects would receive a score of zero. With a severe stroke, a person might receive a score of 25 or higher. Some researchers have shown that the patient's initial stroke scale score correlates well to his or her overall outcome. In other words, a low score suggests a good prognosis whereas a high score suggests a poor one.
Many different health care providers can use the NIH stroke scale to assess a patient. Although often physicians — either emergency room doctors or neurologists — administer the test, other health professionals can also be trained in how to use this clinical tool. A patient can even be assessed by a health care provider using telemedicine, meaning that a doctor located at a central location can assess a patient located far away with the use of real-time video.
Often a patient’s NIH stroke scale score is evaluated immediately on presentation to the emergency room. If patients receive a treatment for an acute stroke, such as an intravenous thrombolytic agent that helps to break up blood clots that could be causing the stroke, the patient's score is re-calculated two hours after the treatment is given. Often patients are then evaluated 24 hours, seven days, and three months after the initial onset of symptoms. The patient's position on the scale therefore serves as a marker of how well he or she has recovered from an acute stroke.