The National Institutes of Health Stroke Scale, or NIH Stroke Scale (NIHSS) is a tool used by healthcare providers to objectively quantify the impairment caused by a stroke. The NIHSS is composed of 11 items, each of which scores a specific ability between a 0 and 4. For each item, a score of 0 typically indicates normal function in that specific ability, while a higher score is indicative of some level of impairment. The individual scores from each item are summed in order to calculate a patient's total NIHSS score. The maximum possible score is 42, with the minimum score being a 0.
Contents
- Performing the scale
- 1 Level of Consciousness
- A LOC Responsiveness
- B LOC Questions
- C LOC Commands
- 2 Horizontal Eye Movement
- 3 Visual field test
- 4 Facial Palsy
- 5 Motor Arm
- 6 Motor Leg
- 7 Limb Ataxia
- 8 Sensory
- 9 Language
- 10 Speech
- 11 Extinction and Inattention
- Usage
- NIHSS use in tPA eligibility
- NIHSS structure
- Modified National Institutes of Health Stroke Scale
- Accuracy
- Effect of stroke location on NIHSS prediction of stroke severity
- NIHSS as predictor of patient outcomes
- Other Stroke Measurements
- References
Performing the scale
While administering the NIHSS it is important that the examiner does not coach or help with the assigned task. The examiner may demonstrate the commands to patients that are unable to comprehend verbal instructions, however the score should reflect the patient's own ability. It is acceptable for the examiner to physically help the patient get into position to begin the test, but the examiner must not provide further assistance while the patient is attempting to complete the task. For each item the examiner should score the patient's first effort, and repeated attempts should not affect the patient's score. An exception to this rule exist in the language assessment (Item 9) in which the patient's best effort should be scored. Some of the items contain "Default Coma Scores", these scores are automatically assigned to patients that scored a 3 in item 1a.
1. Level of Consciousness
Level of consciousness testing is divided into three sections. The first LOC items test for the patient's responsiveness. The second LOC item is based on the patient's ability to answer questions that are verbally presented by the examiner. The final LOC sub-section is based on the patient's ability to follow verbal commands to perform simple task. Although this item is broken into three parts, each sub-section is added to the final score as if it is its own item.
A) LOC Responsiveness
Scores for this item are assigned by a medical practitioner based on the stimuli required to arouse patient. The examiner should first assess if the patient is fully alert to his or her surroundings. If the patient is not completely alert, the examiner should attempt a verbal stimulus to arouse the patient. Failure of verbal stimuli indicates an attempt to arouse the patient via repeated physical stimuli. If none of these stimuli are successful in eliciting a response, the patient can be considered totally unresponsive.
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B) LOC Questions
Patient is verbally asked his or her age and for the name of the current month.
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C) LOC Commands
The patient is instructed to first open and close his or her eyes and then grip and release his or her hand
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2. Horizontal Eye Movement
Assesses ability for patient to track a pen or finger from side to side only using his or her eyes. This is designed to assess motor ability to gaze towards the hemisphere opposite of injury. This item is tested because Conjugated eye deviation is present in approximately 20% of stroke cases. CED is more commons in right hemispheric strokes and typically in lesions effecting the basal ganglia and temporoparietal cortex. Damage to these areas can result in decreased spatial attention and reduced control of eye movements.
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3. Visual field test
Assess the patient's vision in each visual fields. Each eye is tested individually, by covering one eye and then the other. Each upper and lower quadrant is tested by asking the patient to indicate how many fingers the investigator is presenting in each quadrant. The investigator should instruct the patient to maintain eye contact throughout this test, and not allow the patient to realign focus towards each stimulus. With the first eye covered, place a random number of fingers in each quadrant and ask the patient how many fingers are being presented. Repeat this testing for the opposite eye.
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4. Facial Palsy
Facial palsy is partial or complete paralysis of portions of the face. Typically this paralysis is most pronounced in the lower half of one facial side. However, depending on lesion location the paralysis may be present in other facial regions. While inspecting the symmetry of each facial expression the examiner should first instruct patient to show his or her teeth (or gums). Second, the patient should be asked to squeeze his or her eyes closed as hard as possible. After reopening his or her eyes, the patient is then instructed to raise his or her eyebrows.
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5. Motor Arm
With palm facing downwards, have the patient extend one arm 90 degrees out in front if the patient is sitting, and 45 degrees out in front if the patient is lying down. If necessary, help the patient get into the correct position. As soon as the patient's arm is in position the investigator should begin verbally counting down from 10 while simultaneously counting down on his or her fingers in full view of the patient. Observe to detect any downward arm drift prior to the end of the 10 seconds. Downward movement that occurs directly after the investigator places the patient's arm in position should not be considered downward drift. Repeat this test for the opposite arm. This item should be scored for the right and left arm individually, denoted as item 5a and 5b.
Notes
6. Motor Leg
With the patient in the supine position, one leg is placed 30 degrees above horizontal. As soon as the patient's leg is in position the investigator should begin verbally counting down from 5 while simultaneously counting down on his or her fingers in full view of the patient. Observe any downward leg drift prior to the end of the 5 seconds. Downward movement that occurs directly after the investigator places the patient's leg in position should not be considered downward drift. Repeat this test for the opposite leg. Scores for this section should be recorded separately as 6a and 6b for the left and right legs respectively.
Notes
7. Limb Ataxia
This test for the presence of a unilateral cerebellar lesion, and distinguishes a difference between general weakness and incoordination. The patient should be instructed to first touch his or her finger to the examiner's finger then move that finger back to his or her nose, repeat this movement 3-4 times for each hand. Next the patient should be instructed to move his or her heel up and down the shin of his or her opposite leg. This test should be repeated for the other leg as well.
Notes
8. Sensory
Sensory testing is performed via pinpricks in the proximal portion of all four limbs. While applying pinpricks, the investigator should ask whether or not the patient feels the pricks, and if he or she feels the pricks differently on one side when compared to the other side.
Notes
9. Language
This item measures the patient's language skills. After completing items 1-8 it is likely the investigator has gained an approximation of the patient's language skills; however it is important to confirm this measurement at this time. The stroke scale includes a picture of a picture of a scenario, a list of simple sentences, a figure of assorted random objects, and a list of words. The patient should be asked to explain the scenario depicted in the first figure. Next, he or she should read the list of sentences and name each of the objects depicted in the next figure. The scoring for this item should be based on both the results from the test performed in this item in addition to the language skills demonstrated up to this point in the stroke scale.
Notes
10. Speech
Dysarthria is the lack of motor skills required to produce understandable speech. Dysarthria is strictly a motor problem, and is not related to the patient's ability to comprehend speech. Strokes that cause dysarthria typically affect areas such as the anterior opercular, medial prefrontal and premotor, and anterior cingulate regions. These brain regions are vital in coordinating motor control of the tongue, throat, lips, and lungs. To perform this item the patient is asked to read from the list of words provided with the stroke scale while the examiner observes the patient's articulation and clarity of speech.
Notes
11. Extinction and Inattention
Sufficient information regarding this item may have been obtained by the examiner in items 1-10 to properly score the patient. However, if any ambiguity exist the examiner should test this item via a technique referred to as "double simultaneous stimulation". This is performed by having the patient close his or her eyes and asking him or her to identify the side on which they are being touched by the examiner. During this time the examiner is alternating between touching the patient on the right and left side. Next, the examiner touches the patient on both sides at the same time. This should be repeated on the patients face, arms, and legs. To test extinction in vision, the examiner should hold up one finger in front of each of the patient's eyes and ask the patient to determine which finger is wiggling or if both are wiggling. The examiner should then alternate between wiggling each finger and wiggling both fingers at the same time.
Notes
Usage
The NIHSS was designed to be a standardized and repeatable assessment of stroke patients utilized by large multi-center clinical trials. Clinical researchers have widely accepted this scale due to high levels of score consistency. Consistency of NIHSS scores has been demonstrated in inter-examiner and in test-retest scenarios. Clinical research use of the NIHSS typically involves obtaining a baseline NIHSS score as soon as possible after onset of stroke symptoms The NIHSS is then repeated at regular intervals or after significant changes in patient condition. This history of scores can then be utilized to monitor the effectiveness of treatment methods and quantify a patient’s improvement or decline. The NIHSS has also been used in a prospective observational study, to predict 3 month outcomes of patients with undernutrition during hospital stays directly after a stroke.
NIHSS use in tPA eligibility
NIHSS has gained popularity as a clinical tool utilized in treatment planning. Minimum and maximum NIHSS scores have been set for multiple treatment options in order to assist physicians in choosing an appropriate treatment plan.Tissue plasminogen activator (tPA), a type of Thrombolysis is currently the only proven treatment for acute ischemic strokes. Ischemic strokes are the result of blood clots that are preventing blood flow within a cerebral blood vessel. The goal of tPA treatment is to break up the clots that are occluding the vessel, and restore cerebral blood flow. Treatment with tPA has been shown to improve patient outcome in some studies and to be harmful in others. The effectiveness and risk of tPA is strongly correlated with the delay between stroke onset and tPA delivery. Current standards recommend for tPA to be delivered within 3 hours of onset, while best results occur when treatment is delivered within 90 minutes of onset. Since the NIHSS has been established as a quick and consistent quantifier of stroke severity, many physicians have looked to NIHSS scores as indicators for tPA treatment. This rapid assessment of stroke severity is targeted to reduce delay of tPA treatment. Some hospitals use an NIHSS of less than 5 to exclude patients from tPA treatment, however the American Heart Association urges against NIHSS scores being used as the sole reason for declaring a patient as ineligible for tPA treatment.
NIHSS structure
In an effort to produce a complete neurological assessment the NIHSS was developed after extensive research and multiple iterations. The goal of the NIHSS was to accurately measure holistic neurological function by individually testing specific abilities. NIHSS total score is based on the summation of 4 factors. These factors are left and right motor function and left and right cortical function. The NIHSS assesses each of these specific functions by the stroke scale item listed in the chart below.
Modified National Institutes of Health Stroke Scale
The Modified NIH Stroke Scale (mNIHSS) is a shortened, validated version of the mNIHSS. It has been shown to be equally, if not more, accurate than the longer, older NIHSS. It removes questions 1A, 4, and 7. This makes the mNIHSS shorter and easier to use. The mNIHSS predicts patients at high risk of hemorrhage if given Tissue plasminogen activator (tPA) and which patients are likely to have good clinical outcomes. The mNIHSS has also recently been shown to be taken without seeing the patient, and only using medical records. This potentially improves care while in the emergency room and the hospital, but also facilitates retrospective research.
Accuracy
The National Institutes of Health Stroke Scale has been repeatedly validated as a tool for assessing stroke severity and as an excellent predictor for patient outcomes. Severity of a stroke is heavily correlated with the volume of brain affected by the stroke, strokes effecting larger portions of the brain tend to have more detrimental effects. NIHSS scores have been found to be reliable predictors of damaged brain volume, with a smaller NIHSS score indicating a smaller lesion volume
Effect of stroke location on NIHSS prediction of stroke severity
Due to the NIHSS’s focus on cortical function, patients suffering from a cortical stroke tend to have higher (worse) baseline scores. The NIHSS places 7 of the possible 42 points on abilities that require verbal skills; 2 points from the LOC questions, 2 points from LOC commands, and 3 points from the Language item. The NIHSS only awards 2 points for extinction and inattention. Approximately 98% of humans have verbal processing take place in the left hemisphere, indicating that the NIHSS places more value on deficits in the left hemisphere. This results in lesions receiving a higher (worse) score when occurring in the left hemisphere, compared to lesions of equal size in the right hemisphere. Due to this emphasis, the NIHSS is a better predictor of lesion volume in the strokes occurring within the left cerebral hemisphere.
NIHSS as predictor of patient outcomes
The NIHSS has been found to be an excellent predictor of patient outcomes. A baseline NIHSS score greater than 16 indicates a strong probability of patient death, while a baseline NIHSS score less than 6 indicates a strong probability of a good recovery. On average, an increase of 1 point in a patient’s NIHSS score decreases the likelihood of an excellent outcome by 17%. However, correlation between functional recovery and NIHSS scores was weaker when the stroke was isolated to the cortex.