NIH Stroke Scale (NIHSS)

NIH stroke scale

In order to evaluate the neurological function, specific abilities are tested. The targeted areas are the left and right motor function and left and right cortical.

The full examination can easily be performed by physicians, nurses or other medical professionals, as long as they have received training on the method.

The National Institutes of Health Stroke Scale (NIHSS) is meant to standardize stroke assessment and is currently used in numerous medical facilities and clinical trials around the world.

The score provides a start point for management of the condition and recovery after it but can also be used to track outcomes in the following 3 to 12 months whether the patient condition improves or deteriorates.

The first instruction for the examiner is not to provide any assistance to the patient in completing the tasks and that the first attempt is scored.

1. Level of Consciousness (LOC):

The first part of the scale consists of three individual tasks that assess the patient’s responsiveness to stimuli, the ability to answer questions and the ability to understand and follow simple verbal commands.

1A. LOC Responsiveness

■ Alert, responsive patient (0 points);

■ Not alert, verbally arousable or to minor stimulation to obey, answer or respond (1 point);

■ Not alert, arousable to repeated, intense or painful stimuli to create movement (2 points);

■ Totally unresponsive, reflex motor or autonomic effects or areflexic (3 points).

This item depends on the stimuli required to arouse the patient. Stimulus intensity should be increased gradually, starting from verbal to physical stimulation. If none of the methods employed is successful, the patient is rated as totally unresponsive.

Attention: The selection of the totally unresponsive answer implies that the default coma score can be automatically chosen in the following sections of the scale when applicable.

1B. LOC Questions

■ The patient answers both questions correctly (0 points);

■ The patient answers one of the questions correctly (1 point);

■ The patient doesn’t answer any of the questions correctly or at all (2 points);

The questions in this section refer to the current month and age of the patient, who should not be prompted with clues. In case the patient is prevented from speaking in any way, a written answer is accepted.

If the patient cannot speak due to trauma, dysarthria or intubation, a score of 1 point is automatically awarded. Aphasic patients are awarded 2 points.

1C. LOC Commands

■ Correct performance of both tasks (0 points);

■ Correct performance of just one of the tasks (1 point);

■ Incorrect or no performance of either of the tasks (2 points).

The ability of the patient to follow simple commands such as opening and closing of eyes, grip and release of hands, is evaluated.

Commands should only be given once, the intensity of the action is not rated, but its completion and the commands will not be repeated.

If the patient cannot use their hands, the grip task will be replaced by a similar one.

2. Horizontal eye movement:

■ Normal ability to follow pen or finger to both sides (0 points);

■ Partial gaze palsy, abnormal in either one or both eyes. Patient can gaze towards affected hemisphere but not past midline (1 point);

■ Total gaze paresis with gaze fixed to one side (2 points).

In approximately 20% of stroke cases, a conjugated eye deviation is present, therefore the patient suffers from decreased spatial attention and has a reduced control over eye movements.

The ability of the patient to track an object is assessed by the movement of a pen or finger from side to side. The task determines motor gazing ability towards the hemisphere opposite of the presumptive injury.

3. Visual field:

■ No vision loss (0 points);

■ Partial hemianopia or complete quadrantanopia (1 point);

■ Complete hemianopia – no visual stimulation in half of the visual field (2 points);

■ Bilateral Blindness (3 points).

The patient’s vision in each visual field is evaluated for each eye separately while the other is covered. The upper and lower quadrants are tested by showing a number of fingers in that quadrant and asking the patient to count them.

For non-responsive patients the finger test should be replaced with the movement of an object towards the eyes for every tested quadrant and observing the patient reaction.

If there is unilateral blindness or enucleation, only the remaining eye is evaluated. If a clear-cut asymmetry, including quadrantanopia, is found, 1 point is awarded by default.

4. Facial palsy:

■ Normal and symmetrical movement (0 points);

■ Minor paralysis with minor asymmetry or flattened nasolabial fold (1 point);

■ Partial paralysis in lower face (2 points);

■ Complete facial hemiparesis (total paralysis of upper and lower areas of half face) (3 points).

This item checks for partial or complete paralysis of the face by observing the facial symmetry in different types of movement such as the showing of the teeth or gums, squeezing of eyes closed or raising eyebrows.

Any bandage, orotracheal tube or other physical barriers obscuring the face are to be removed during this evaluation.

5A/5B. Motor arm:

■ No arm drift for the whole duration of the task (0 points);

■ Drift to an intermediate position but without any support (1 point);

■ The arm obtains the initial position but drifts down to support before the end of the count (2 points);

■ No effort against gravity as the arm falls immediately after being helped in the initial position (3 points);

■ No voluntary movement (4 points);

■ Default coma score for both arms test (8 points).

The patient is required to extend one arm 90 degrees out (sitting) or 45 degrees out (lying down) with the palm facing downwards. This position should be maintained whilst the assessor counts backwards from 10 to 1 (using fingers in full view of patient).

Any downward arm drift before the count is finished counts towards the scoring. The task is repeated for the other arm as well. The rating is 5A for right arm and 5B for left arm. In case one or both arms are amputated, the medical professional should make a note of this.

6A/6B. Motor leg:

■ No leg drifts for the whole duration of the task (0 points);

■ The leg drifts to an intermediate position, without support before the count is up (1 point);

■ Limited effort against gravity, the leg drifts to support before the count is up (2 points);

■ No effort against gravity, the leg falls immediately after being put in the initial position (3 points);

■ No voluntary movement (4 points);

■ Default coma score for both legs test (8 points).

The patient is placed in supine position with one leg placed 30 degrees above horizontal and this position should be maintained whilst the assessor counts backwards from 5 to 1 (also using fingers in full view of patient).

Each leg performance is scored separately. In case one or both legs are amputated, there should be made note of this.

7. Limb ataxia:

■ Normal coordination, accurate movement (0 points);

■ Ataxia present in one limb that is rigid and provides inaccurate movement (1 point);

■ Ataxia present in two or more limbs, rigid, inaccurate movement in limbs of one side (2 points).

This item checks for the presence of a unilateral cerebellar lesion and distinguishes between general weakness and lack of coordination.

Firstly, the patient is asked to touch his finger to the assessor’s finger then move the finger to his own nose. This action should be repeated 3, 4 times with each hand.

Secondly, the patient is asked to move the heel up and down the shin of the opposite leg and repeat this action for the bilateral leg as well.

Ataxia is scored only if present out of proportion to weakness and is considered absent in case the patient cannot understand the commands or is paralyzed.

8. Sensory test:

■ No evidence of sensory loss (0 points);

■ Mild to moderate sensory loss, different sensation between the two sides of the body (1 point);

■ Severe or total loss of sensation to unilateral extremities that can be clearly demonstrated (2 points);

■ No response, quadriplegic, coma (2 points).

This item checks for sensory loss after stroke. It uses pinprick stimulation in the proximal portion of all four limbs.

The patient is asked about what they feel, how much they feel and whether they notice any differences in sensation from one side to another.

9. Language:

■ Normal skills, no obvious speech deficit (0 points);

■ Mild to moderate aphasia with a certain loss of fluency but enough information extracted during the tasks with some reduction in comprehension (1 point);

■ Severe aphasia with fragmented speech and limited context (2 points);

■ Unable to speak, global aphasia or auditory comprehension (3 points);

■ Default Coma Score (3 points).

This item evaluates the patient’s language skills using a picture of a scenario, a picture figuring random objects, a list of words and another of sentences.

The patient will be asked to describe the scenario in the first picture, name the objects in the second and read the words and the sentences.

The result of this evaluation should also consider the language skills displayed by the patient during the other 8 scale tasks as well. In case the patient is intubated, if possible, the answers can be written down.

Visual material used in the NIHSS language assessment:

10. Speech:

■ Normal speech (0 points);

■ Mild to moderate dysarthria, speech slurring but speech is not completely impaired (1 point);

■ Severe dysarthria, slurred speech, hardly understandable or complete lack of speech (2 points).

This items checks whether dysarthria is present or not and whether a motor problem is present, thus interfering with patient communication but with no connection to the ability to comprehend commands.

The patient is asked to read a list of words and their clarity of speech and articulation are evaluated.

In case the patient is intubated, this item will be disregarded.

11. Extinction and inattention:

■ No observed abnormality (0 points);

■ Inattention either visual, tactile, auditory or spatial on one side (1 point);

■ Hemi-inattention extinction to more than one: visual, tactile, auditory or spatial with lack of orientation (2 points);

■ Default coma score (2 points).

As the last item in the NIHSS, this combines information obtained along the whole test with the performance at this item, in case there is certain ambiguity about results.

The technique used is commonly referred to as the “double simultaneous stimulation”.

The assessor alternates touching (on the face, arms, legs) the patient on the right and left side and then touches both sides at the same time.

The assessor is to hold one finger in front of each of the eyes of the patient at the same time, wiggle one of the fingers or both and check with the patient which of the fingers is wiggling or if both are.

NIH stroke scale interpretation

To quantify the impairment caused by stroke in the patient, each of the 15 sections awards a score based on patient performance, these scores vary from 0 to 4.

The result obtained in the above form objectively quantifies the stroke impairment in the patient assessed. Each of the 15 sections provides score between 0 and 4.

Scores of 0 indicate a lack of impairment, and with every score increase, the stroke effects are more consistent. The maximum obtainable in NIHSS is 42.

The association between NIHSS scores and the severity of stroke symptoms is presented in the table below:

Score	Stroke Severity
0	No stroke symptoms
1 - 4	Minor stroke
5 - 15	Moderate stroke
16 - 20	Moderate to severe stroke
21 - 42	Severe stroke

About the original study

The National Institutes of Health Stroke Scale was devised as a way to ensure consistency and the same procedures are followed in the evaluation of stroke patients in multicentre therapeutic stroke trials.

The consistency of NIHSS results has been proved through both inter-examiner and in test-retest scenarios.

The study consisted in the measuring of the effectiveness of training about the method for 162 investigators, each evaluating a set of 11 patients on camera. Measures of interobserver agreement were calculated.

Most NIHSS items were found to have moderate to excellent agreement whilst only two items, facial paresis and ataxia were found to generate poor agreement.

Patrick D. Lyden MD is chair of the Department of Neurology, Director of the Stroke Program and holds the Carmen and Louis Warschaw Chair in Neurology at Cedars-Sinai. His main research focus is in stroke intervention.

Original source

Lyden P, Brott T, Tilley B, Welch KM, Mascha EJ, Levine S, Haley EC, Grotta J, Marler J. Improved reliability of the NIH Stroke Scale using video training. NINDS TPA Stroke Study Group. Stroke. 1994; 25(11):2220-6.

Validation

Johnston KC, Connors AF Jr, Wagner DP, Haley EC Jr. Predicting outcome in ischemic stroke: external validation of predictive risk models. Stroke. 2003; 34(1):200-2.

Other references

1. Brott T, Adams HP Jr, Olinger CP, Marler JR, Barsan WG, Biller J, Spilker J, Holleran R, Eberle R, Hertzberg V, et al. Measurements of acute cerebral infarction: a clinical examination scale. Stroke. 1989; 20(7):864-70.

2. Intracerebral hemorrhage after intravenous t-PA therapy for ischemic stroke. The NINDS t-PA Stroke Study Group. Stroke. 1997; 28(11):2109-18.