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 and aid planning post-acute care disposition, though was intended to assess differences in interventions in clinical trials. The NIHSS was designed for the National Institute of Neurological Disorders and Stroke (NINDS) Recombinant Tissue Plasminogen Activator (rt-PA) for Acute Stroke Trial and was first published by neurologist Dr. Patrick Lyden and colleagues in 2001. Prior to the NIHSS, during the late 1980s, several stroke-deficit rating scales were in use (e.g., University of Cincinnati scale, Canadian neurological scale, the Edinburgh-2 coma scale, and the Oxbury initial severity scale). 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.
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. Note that the NIHSS may fluctuate depending on the time.
1. Level of consciousness (LOC) Level of consciousness (LOC) 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 their 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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If patients scores a 3 in this factor, the default coma scores should be used when applicable
B) LOC questions Patient is verbally asked their age and for the name of the current month.
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Default Coma Score: 2 The patient must answer each question 100% correct without help to get credit Patients unable to speak are allowed to write the answer Aphasic patients or patients in a stuporous state who are unable to understand the commands receive a score of 2 Patients that are unable to talk due to trauma, dysarthria, language barrier, or intubation are given a score of 1
C) LOC commands The patient is instructed to first open and close their eyes and then grip and release their hand.
Notes
Commands can only be repeated once. The hand grip command can be replaced with any other simple one step command if the patient cannot use their hands. A patient's attempt is regarded as successful if an attempt is made but is incomplete due to weakness. If the patient does not understand the command, the command can be visually demonstrated to them without an impact on their score. Patients with trauma, amputations, or other physical impediments can be given other simple one-step commands if these commands are not appropriate.
2. Horizontal eye movement Assesses ability for patient to track a pen or finger from side to side only using their eyes. This is designed to assess motor ability to gaze towards the hemisphere opposite of injury. This item is tested because conjugated eye deviation (CED) is present in approximately 20% of stroke cases. CED is more common in right hemispheric strokes and typically in lesions affecting 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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If patient is unable to follow the command to track an object, the investigator can make eye contact with the patient and then move side to side. The patient's gaze palsy can then be assessed by their ability to maintain eye contact. If patient is unable to follow any commands, assess the horizontal eye movement via the oculocephalic maneuver. This is done by manually turning the patient's head from midline to one side and assessing the eye's reflex to return to a midline position. If the patient has isolated peripheral nerve paresis assign a score of 1.
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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