The NIH Stroke Scale (NIHSS)

The NIH Stroke Scale (NIHSS) is a standardized scoring assessment used during a neurological exam after someone has had a stroke. It measures aspects of brain function, including consciousness, vision, sensation, movement, speech, and language.

The NIHSS is a standardized tool used by clinicians and researchers to measure and record the level of impairment caused by a stroke.

This article discusses the components of the NIHSS, when it is given, and how it is used.

What Is a Stroke?

A stroke is a serious health condition that occurs when the blood supply to a part of the brain is blocked or when a blood vessel in the brain bursts. When blood flow to the brain is blocked or restricted, parts of the brain become damaged or die. 

Stroke effects depend on which area of the brain is affected and can include physical weakness, loss of balance, decreased sensation, trouble speaking, and a number of other problems.

The severity of a stroke varies depending on the size and extent of the blockage. 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.

NIHSS score is usually first determined in the emergency department, as soon as possible after the onset of stroke symptoms. It will also be applied at regular intervals, and/or whenever the person's condition changes significantly (either improving or declining).

The NIHSS contains 15 questions covering 11 elements that measure specific functions. The elements include:

• Level of consciousness: Evaluates alertness and responsiveness to a simple question or command
• Best gaze: Measures a person's ability to move their eyes by asking them to follow an object
• Visual: Tests the visual field—the ability to see things that are not directly in front of you
• Facial palsy: Measures the ability to move facial muscles
• Motor arm: Evaluates the person's ability to hold their arms up without drifting for up to 10 seconds
• Motor leg: Tests the ability to hold each leg up at 30 degrees for at least five seconds
• Limb ataxia: Measures whether a person can touch a finger to the nose and run the heel down the shin on each side
• Sensory: Assesses the reaction to an unpleasant smell and to a pinprick on the face, arms, trunk, and legs
• Best language: Measures the loss of fluency and limitations on ideas that can be expressed
• Dysarthria: Determines the level of slurred speech
• Extinction and inattention: Looks at a person's level of attention to their environment and their general sensory abilities in each of the five senses

Each element is evaluated with a numerical score. The higher the number, the greater impairment for that specific function. 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

How Is the NIH Stroke Scale Used?

The NIHSS is used for several different purposes, including guiding treatment decisions and providing a standard scale for researchers and clinicians to use.

To Guide Clinical Decisions

The NIHSS serves as the foundation for clinical decision-making when a patient arrives at the hospital presenting with a stroke. Joint guidelines from the American Heart Association and the American Stroke Association recommend the use of NIHSS to quantify the degree of neurological deficit, facilitate communication, and identify patients suitable for treatment with tPA (tissue plasminogen activator).

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.

As a 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.

To Help Healthcare Providers Communicate

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 convey 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.

How the Score Predicts Prognosis

A person's prognosis related to NIHSS scores at admission to the emergency room are as follows:

• Scores of less than 5: About 80% of stroke survivors will be discharged to home.
• Scores between 6 and 13: Stroke survivors typically require acute inpatient rehabilitation.
• Scores of greater than 14: Stroke survivors frequently require long-term skilled care.

The validity of the NIHSS is reduced if:

• There is a language barrier.
• The patient previously had a neurological deficit.
• The patient is intubated (a tube in the trachea for breathing).

Summary

The NIH Stroke Scale (NIHSS) is a standardized scoring assessment used during a neurological exam after a stroke to measure aspects of brain function. The NIHSS is a standardized tool that measures and records the level of impairment caused by a stroke. It is used to guide treatment decisions, as a research tool, and to help measure changes in your condition.