The NIH Stroke Scale (NIHSS)

A Tool Used for Stroke Evaluation

The NIH Stroke Scale (NIHSS) is a standardized scoring tool used by healthcare provider 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 fifth most common 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 means 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 which region of the brain is affected, 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 levels of stroke severity as measured by the NIHSS scoring system are:

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

NIH Stroke Scale Use

The NIHSS is used for several different purposes, including guiding treatment decisions and providing a standard scale for researchers and clinicians to 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 outcomes, but it can only be used in limited situations. NIHSS also provides a basis for healthcare providers 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.

Communication Among Healthcare Providers

In general, neurologists and other healthcare 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 healthcare providers look at when assessing your condition and making treatment decisions.

However, the uniformity of the scale can help your healthcare 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 healthcare 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 assess your recovery after a stroke.

4 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. American Heart Association. Stroke falls to No. 5 killer in U.S.

  2. Lui SK, Nguyen MH. Elderly stroke rehabilitation: Overcoming the complications and its associated challenges. Curr Gerontol Geriatr Res. 2018;2018:9853837. doi:10.1155/2018/9853837

  3. Harrison JK, Mcarthur KS, Quinn TJ. Assessment scales in stroke: Clinimetric and clinical considerations. Clin Interv Aging. 2013;8:201-11. doi:10.2147/CIA.S32405

  4. Powers WJ, Rabinstein AA, Ackerson T, et al; American Heart Association Stroke Council. 2018 Guidelines for the early management of patients with acute ischemic stroke: A guideline for healthcare professionals from the American Heart Association/American Stroke Association. Stroke. 2018 Mar;49(3):e46-e110. doi: 10.1161/STR.0000000000000158.

Additional Reading

By Jose Vega MD, PhD
Jose Vega MD, PhD, is a board-certified neurologist and published researcher specializing in stroke.