NIH Stroke Scale (NIHSS) Calculator

How does this NIH stroke scale calculator work?

This health form tries to measure the neurological function of an individual, especially when stroke is suspected, by testing specific abilities. The targeted areas are the left and right motor function and left and right cortical and the full examination can be performed by physicians, nurses or other medical professionals.

This NIH stroke scale (NIHSS) calculator basically quantifies the stroke severity in the acute setting of acute cerebral infarction and its score is used to track outcomes in the following 3 to 12 months both in terms of improvement or deterioration.

The National Institutes of Health Stroke Scale (NIHSS) is designed as a standardized, easy to implement and repeat stroke assessment and is commonly used in medical facilities and clinical trials. It can evaluate and document the existence of stroke symptoms and their severity and also provide a start guide management of the next directions.

The steps to follow after the assessment include an in depth neurological consult, a determination of the onset of the stroke related symptoms and further imaging such as computer tomography and MRI/MRA.

Performing the NIH stroke scale

While administering the scale, the examiner should not provide any assistance to the patient in completing the tasks and the first effort will be scored, regardless of further repeated attempts.

1. Level of Consciousness LOC

The first part of the scale comprises of three individual tasks that assess the patient’s responsiveness, the ability to answer questions and the ability to follow simple verbal commands. Each of the three tasks provides a score to be summed at the end of the test.

1A. LOC Responsiveness

Scores are given according to 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 considered totally unresponsive.

Attention: Choosing the totally unresponsive answer and scoring 3 points in this section means that the default coma score can be automatically chosen in the following sections of the scale when applicable.

■ 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).

1B. Questions

The assessor may ask the patient about the current month and about their age and they should not help the patient in any way. In case the patient is prevented from speaking in any way, a written answer is accepted.

If this is not possible and the patient cannot speak due to trauma, dysarthria or intubation, a score of 1 point is automatically awarded. A score of 2 points applies in the case of aphasic patients.

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

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

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

1C. Commands

The assessor observes the ability of the patient to understand and follow simple commands, the opening and closing of the eyes, grip and release of hands.

It is important that the commands are given just once and not repeated and that only the first attempt to be scored. In case the patient is unable to use their hands, due to trauma, amputation or other physical impairment, this task should be replaced with a similar one. Attempts varying in intensity due to patient weakness are considered successful if complete.

■ 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).

2. Horizontal eye movement

The assessor test the patient’s ability to track using his or her eyes, an object, pen or finger from side to side. This task determines motor gazing ability towards the hemisphere opposite of the presumptive injury.

In approximately 20% of stroke cases, a conjugated eye deviation is present leading to decreased spatial attention and a reduced control over eye movements.

■ 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).

3. Visual field

This test assesses the patient’s vision in each of the visual fields, having each eye tested individually 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. In case the patient is non responsive 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, visual fields in the remaining eye are scored. If a clear-cut asymmetry, including quadrantanopia, is found, should be awarded 1 point.

■ 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).

4. Facial palsy

The medical professional checks whether there is partial or complete paralysis of the face. Certain facial regions can be affected depending on the location of the lesion, typically paralysis being more pronounced in the lower half of one side.

This test observes facial symmetry in different types of movement such as the patient being asked to show teeth or gums, to squeeze eyes closed and to raise eyebrows. Any bandage, orotracheal tube or other physical barriers obscuring the face should be removed.

■ 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) (3points).

5. Motor arm

This task involves having the patient extend one arm 90 degrees out (sitting) or 45 degrees out (lying down) with the palm facing downwards. The patient should maintain the position while the assessor counts down from 10, also using his fingers in the full view of the patient.

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

5A/5B

■ 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).

6. Motor leg

This task involved the patient in the supine position with one leg placed 30 degrees above horizontal and once the leg is placed in the initial position, the assessor should count down from 5, also using his fingers in the full view of the patient. The same should be repeated for the other leg.

Any downward movement before the count is up should be recorded. 6A and 6B note performance for each leg. In case one or both legs are amputated, there should be made note of this.

■ 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).

7. Limb ataxia

Assessor checks for the presence of a unilateral cerebellar lesion and has to distinguish between general weakness and lack of coordination.

In the first part of this test, the patient is put to touch his finger to the assessor’s finger than move the finger to his own nose. This action should be repeated 3, 4 times for each hand.

In the second part, the patient has to move the heel up and down the shin of the opposite leg and repeat this action for the other 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.

■ 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).

8. Sensory test

This section is performed in order to check for sensory loss due to stroke using pinpricks in the proximal portion of all four limbs, during which application, the examiner demands whether the patient feels the pricks, how it feels them and whether there are differences in feeling between the two sides.

■ 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).

9. Language

The examiner tries to assess the patient’s language skills using a picture of a scenario, a picture figuring random objects, a list of words and one of sentences. The patient is asked to describe the scenario in the first picture, name the objects in the second and read the words and the sentences.

The assessor should also take into account the language skills displayed during the other 8 scale tasks as well. Certain parts can be repeated and the best response should be recorded. In case the patient is intubated, writing the answers can provide a solution.

■ 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).

Visual material used in the NIHSS language assessment

10. Speech

This sequence of the NIHSS examination observes whether dysarthria is present or not and whether a motor problem is present with no connection to the patient’s ability to comprehend commands.

The presence of dysarthria suggests that a possible stroke might have affected areas such as the anterior opercular, medial prefrontal and premotor, and anterior cingulate regions meaning that the motor control of the tongue, throat and lips is impaired, thus making speech difficult or impossible.

The examiner will ask the patient to read the list of words and will observe clarity of speech and articulation. In case the patient is intubated, this sequence will be disregarded.

■ 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).

11. Extinction and inattention

This is the last test in the NIH stroke scale and combines information obtained along the whole test, with this last task in care there is certain ambiguity. The technique used in this task is commonly referred to as the “double simultaneous stimulation”.

The examiner should alternate touching (face, arms, legs) the patient on the right and left side and then touches both sides at the same time. Another task 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.

■ No observed abnormality (0 points);

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

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

■ Default coma score (2 points).

NIH stroke scale interpretation

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. Consistency of NIHSS results is widely demonstrated through both inter-examiner and in test-retest scenarios.

Scores close to 0 indicate a lack of or mild impairment while as the score progresses, the stroke effects are becoming more consistent. The overall results in the NIHSS ranges between 0 and 42 and the following table presents the stroke severity assessment based on result categories.

References

1) National Institute of Health, National Institute of Neurological Disorders and Stroke. NIH Stroke Scale.

2) Brott T, Adams HP Jr, Olinger CP, et. al. (1989) Measurements of acute cerebral infarction: a clinical examination scale. Stroke;20(7):864-70.

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