CHAPTER 39: NATIONAL INSTITUTES OF HEALTH STROKE SCALE (NIHSS)

Description

The National Institutes of Health Stroke Scale (NIHSS) is a standardized assessment designed to measure stroke severity and is considered unique in that it assesses the spectrum of neurological deficits that present following a stroke rather than simply concentrating on motor deficits like many other outcome measures (Dewey et al., 1999). Both an interactive and observational tool, it allows the clinician to evaluate and document neurological status, determine treatment options, anticipate discharge planning, as well as measure patient outcomes across several domains such as level of consciousness, extra-ocular movements, visual fields, facial muscle function, extremity strength, coordination, sensory function, language, speech, and hemi-attention (neglect) (Dancer, Brown, & Yanase, 2009). First designed as a 15-item scale in 1989, it has been modified to include 13- and 11-item versions; however, the original remains the most commonly used. An example item of the assessment is facial palsy, where the subject is encouraged, often through pantomime, to show their teeth or raise their eyebrows and close their eyes, which is scored as (0) normal symmetrical movements, (1) minor paralysis (flattened nasolabial fold, asymmetry on smiling), (2) partial paralysis (total or near-total paralysis of lower face), or (3) complete paralysis of one or both sides (absence of facial movement in the upper and lower face) (Appelros & Terent, 2004). The NIHSS can be administered as early as 1 hour after the onset of symptoms as well as > 3 months post-cerebrovascular accident (CVA) and has a scoring range from 0 to 42, where 0 indicates no clinically relevant neurological abnormality and a score of 20 or higher is suggestive of dense paralysis with impaired consciousness (Jain, Van Houten, & Sheikh, 2016). The NIHSS can be completed in less than 10 minutes.

Psychometrics

A study using 2 series of 4 patients rated at baseline and 3 months by 30 physicians and 29 non-physician study coordinators determined that intra-class correlation coefficients to be high at r = 0.93 and 0.95, respectively, reflecting both high levels of intra-rater and inter-rater reliability (Goldstein & Samsa, 1997). A similar reliability study between neurologists and nurses found moderate to excellent agreement for the majority of the NIHSS items except for the sensory component, which only had an agreement range of 0.37 to 0.47 between the 2 health professions (Dewey et al., 1999). A study by Appelros and Terent (2004) established health outcomes by examining scores at baseline and 1 year following a stroke (n = 377) found that the median score of all subjects was 6 (range 3 to 12) at baseline, whereas at follow up it was 1 (range 0 to 3), suggesting good discriminant ability and ability to document change and of the patients that scored less than 4 at baseline 75% were functionally independent after 1 year. Jain et al. (2016) found similar results as NIHSS scores were found to be a strong predictor of both patient discharge disposition and ambulatory status and with every 1-point increase in the stroke scale at baseline, there was a 2.3 times increased likelihood of mortality and 3 times increased likelihood in worsening of ambulatory function.

Advantages

There is a considerable amount of research in support of the NIHSS for use in clinical practice and it is considered to be a gold standard of stroke assessment. The NIH has an excellent interactive website devoted to the assessment where one can find training and certification programs as well as videos and written study material devoted to the measure. Training in use of the NIHSS is also offered by the American Heart Association. Finally, the cross cultural adaptation of the scale has been well established.

Disadvantages

Specialized training may be required for some due to the unique and highly specific stroke and neurologic terminology associated with the measure.

Administration

The NIHSS is typically performed bedside in which the clinician notes the presence, absence, and/or grade of disability relative to items on the assessment. Each question uses variable rating scales (range: 0 to 4) and has detailed instructions. All items are administered in a specific order. The level of instruction is highlighted in the following example of the visual fields item where both the upper and lower quadrants are tested by confrontation, using finger counting or visual threat as appropriate (NIHSS, 2003). The clinician is told that patients may be encouraged, but if he or she is able to look at the side of the moving fingers appropriately, he or she can be scored as normal, whereas if there is unilateral blindness or enucleation, visual fields in the remaining eye are tested and are scored 1 only if there is a clear-cut asymmetry, including if quadrantanopia is present (NIHSS, 2003). If the patient is blind from any cause he or she is scored 3, in which double simultaneous stimulation is then performed. If there is extinction the patient receives a score of 1 (NIHSS, 2003).

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