The NIH Stroke Scale (NIHSS)

NIH Stroke Scale and Stroke Evaluation

The NIH Stroke Scale (NIHSS) is a standardized scoring tool used by physicians and other healthcare professionals to measure and record the level of impairment caused by a stroke. If you have overheard your stroke team discussing your NIHSS or the NIHSS of your loved one, you might have some questions about the meaning behind your score.

Doctor consulting with a nurse in a hospital
Getty Images/ David Sacks

What Is a Stroke?

A stroke is a serious health condition that occurs when blood flow to the brain is either restricted or interrupted. It is the No. 5 cause of death and a leading cause of disability in the United States. Restricted or interrupted blood flow can occur due to a blood clot or a rupture, and lack of blood flow mean vital nutrients and oxygen are unable to make it to the brain. When this happens and the affected region of the brain cannot get what it needs, the brain tissue becomes impaired - which can ultimately result in a physical or cognitive handicap.

Effects of Stroke

The brain is an extremely complex organ that controls various body functions. If a stroke occurs and blood flow can't reach the region that controls a particular body function, that part of the body may not function as it should. Stroke effects can include physical weakness, loss of balance, decreased sensation, trouble speaking and a number of other problems.

Because there are so many different stroke effects depending on the affected region of the brain, not all strokes are considered equal in terms of severity. The NIHSS is a tool by which stroke severity can be compared over time to determine whether a stroke is mild or severe and whether the effects are improving or worsening.

What Does the NIHSS Measure?

The NIHSS measures several aspects of brain function, including: consciousness; vision; sensation; movement; speech; and language. A certain number of points are given for each of these physical and cognitive functions during a focused neurological examination. A maximum score of 42 represents the most severe and devastating stroke.

The level of stroke severity as measured by the NIHSS scoring system:

  • 0 = no stroke
  • 1-4 = minor stroke
  • 5-15 = moderate stroke
  • 15-20 = moderate/severe stroke
  • 21-42 = severe stroke

NIH Stroke Scale Use

Decision Making in Stroke Treatment

The NIHSS serves as the foundation for clinical decision-making when a patient arrives at the hospital presenting with stroke. Joint guidelines from the American Heart Association and the American Stroke Association recommend use of NIHSS to quantify the degree of neurological deficit, facilitate communication and identify patients suitable for treatment with tPA. This medication is a powerful blood thinner that can improve stroke outcome but can only be used in limited situations. NIHSS also provides a basis for doctors to determine changing clinical status - including keeping watch for patients at higher risk for complications such as brain hemorrhage.

Research Tool

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. This can help researchers determine, with uniform criteria, whether a medical treatment is effective in the treatment of stroke.

Consistent Communication Among Health Care Providers

In general, neurologists and other health care providers who take care of you during and after your stroke use detailed clinical records to communicate about your condition. The NIHSS stroke scale is a number that can covey the severity of your stroke but is not the main point that your doctors look at when assessing your condition and making treatment decisions.

However, the uniformity of the scale can help your health care providers get a picture of how much your stroke has improved or worsened over time.

A Word From Verywell

Your healthcare team may use specialized ways to assess and record your medical condition so that everyone on the team will understand how your illness is improving or worsening over time. The NIHSS is one of the tools that your stroke care team uses to communicate in a consistent manner, particularly because there are many different people on your stroke care team who are involved in caring for you as you recover from your stroke. 

The NIHSS is not the only tool used to evaluate and record your condition if you have had a stroke, but you can follow the numbers that your health care providers use when they record your NIHSS severity so that you can get a general idea about your overall progress over time.

Aside from the NIHSS, there is also a post stroke checklist that may be used to asses your recovery after a stroke.

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