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    NIH Stroke Scale/Score (NIHSS)

    Calculates the NIH Stroke Scale for quantifying stroke severity.
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    INSTRUCTIONS

    The NIH Stroke Scale has many caveats buried within it. If your patient has prior known neurologic deficits e.g. prior weakness, hemi- or quadriplegia, blindness, etc. or is intubated, has a language barrier, etc., it becomes especially complicated. In those cases, consult the NIH Stroke Scale website. MDCalc's version is an attempt to clarify many of these confusing caveats, but cannot and should not be substituted for the official protocol.

    Rules:

    • Score what you see, not what you think.
    • Score the first response, not the best response (except Item 9 - Best Language).
    • Don’t coach.
    When to Use
    Pearls/Pitfalls
    Why Use

    The NIHSS can help physicians quantify the severity of a stroke in the acute setting.

    The National Institutes of Health Stroke Scale (NIHSS) was developed to help physicians objectively rate severity of ischemic strokes.

    • Increasing scores indicate a more severe stroke and has been shown to correlate with the size of the infarction on both CT and MRI evaluation.
    • NIHSS scores when assessed within the first 48 hours following a stroke have been shown to correlate with clinical outcomes at the 3-month and 1-year mark.
    • Patients with a total score of 4 or less generally have favorable clinical outcomes and have a high likelihood of functional independence regardless of treatment.

    Points to keep in mind:

    • Many guidelines and protocols warn that administering tPA in patients with a high NIHSS score (>22) is associated with increased risk of hemorrhagic conversion.
    • These patients, however, are also the most severely debilitated and dependent from their strokes as well.
    • Some components of the NIHSS have lower interrater reliability (i.e. facial movement, limb ataxia, neglect, level of consciousness, and dysarthria), and some may be quite limited due to altered mental status, for example.
    • A simpler, modified version of the NIHSS has been found to have greater interrater reliability with equivalent clinical performance, although it has not been as widely adopted as the original NIHSS.
    • The patient with even a large territory posterior circulation stroke syndrome may still have a low or normal NIHSS, highlighting one of its important limitations.

    There are nearly 800,000 cases of acute stroke in the United States every year, with 130,000 associated deaths (4th leading cause of death in Americans).

    The NIHSS can help physicians determine the severity of a stroke, predict clinical outcomes.

    Result:

    Please fill out required fields.

    Next Steps
    Evidence
    Creator Insights

    Advice

    • Consult Neurology immediately (if available) for all patients presenting with ischemic stroke.
    • Evaluate whether the patient is a potential candidate to receive intravenous thrombolysis (tPA).
    • Consider further imaging including CT, CT angiography and MRI/MRA.

    Management

    In patients who present with symptoms concerning for ischemic stroke:

    • Consult Neurology.
    • Determine the onset of stroke symptoms (or time patient last felt or was observed normal).
    • Obtain a stat head CT to evaluate for hemorrhagic stroke.
    • In appropriate circumstances and in consultation with both neurology and the patient, consider IV thrombolysis for ischemic strokes in patients with no contraindications.
    • Always consider stroke mimics in the differential diagnosis, especially in cases with atypical features (age, risk factors, history, physical exam), including:
      • Recrudescence of old stroke from metabolic or infectious stress;
      • Todd’s paralysis after seizure;
      • Complex migraine;
      • Pseudoseizure, conversion disorder

    Critical Actions

    • The NIHSS is broadly predictive of clinical outcomes, but it is important to recognize that individual cases will vary and that management decisions must be made in consultation with the patient whenever possible.
    • Patients with a score of <4 are highly likely to have good clinical outcomes.
    • Whenever possible, patients with acute stroke should be transferred to a stroke center for their initial evaluation and treatment, as the holistic care (medical optimization, early initiation of PT and OT, patient and family education and discharge planning) is associated with improved clinical outcomes; some argue that most of the gains in stroke morbidity and mortality are due to these improvements in stroke care.

    Formula

    Addition of the selected points, as above.

    Facts & Figures

    Language/Aphasia Test

    Language/Aphasia Test

    Dysarthria Test

    dysarthria test

    For more information see the NIH Stroke Scale Website.

    Evidence Appraisal

    • The first iteration of the NIH stroke scale was derived by Brott et al in a pilot study of 10 patients who were evaluated within 3-weeks of having an ischemic stroke.  Authors applied the Toronto Stroke Scale, the Oxbury Initial Severity Scale and the Cincinnati Stroke Scale to these patients, analysed the results and then created a composite scale. This was intended for use in an NIH-sponsored trial of naloxone for stroke (Brott 1989).
    • Brott’s Cincinnati/Naloxone stroke scale was modified by Lyden and colleagues (1994) for use in the National Institute of Neurological Disorders and Stroke (NINDS) study on tissue plasminogen activator (tPA) in patients with ischemic stroke (NINDS 1995).
    • A retrospective review of 1281 subjects with ischemic stroke found that for every 1 point increase in the NIHSS decreased the likelihood of an excellent outcome by 24% at 7 days and 17% at 3 months (Adams 1999).
    • In a trial of 94 patients, authors found that  each 1 point increase in the NIHSS when performed within 24 hours of the stroke correlated with a decreased likelihood of the patient being discharged (Schlegel 2003).
    • A study of 893 patients found that their initial NIHSS score (performed within 72 hours of the ischemic event) was predictive of whether the patient would need to be placed in a nursing home or need to be sent to rehabilitation.  Patients with moderate (6-13 points) or severe (>14 points) NIHSS scores were 3 times more likely to be placed in a nursing home after discharge and 8 more times likely to require rehabilitation therapy (Rundek 2000).
    • A study of 377 patients found that when performed 24-48 hours after an ischemic stroke, that the NIHSS was broadly predictive of group outcomes at 1-year, with 75% of patients who had a score of 4 or less being functionally independent (Appelros 2004).
      • Median score in this study was 6, with 33% of patients dying within the first year after their event.
    • A prospective trial of 54 patients found that combining diffusion weighted MRI imaging with the NIHSS score was more predictive of clinical outcomes at 3 months (70%) than with using the score (43%) or imaging (54%) alone (Yoo 2010).
    • In an analysis of 312 subjects from the NINDS trials, authors found that an NIHSS of >20 was associated with a 17% rate of intracranial hemorrhage with tPA vs. a 3% hemorrhage rate in patients with a score of <10 (The NINDS t-PA Stroke Study Group 1997).

    Literature

    Validation

    Research PaperJohnston KC, Connors AF Jr, Wagner DP, Haley EC Jr. Predicting outcome in ischemic stroke: external validation of predictive risk models. Stroke. 2003 Jan;34(1):200-2.Research PaperAdams HP Jr, Davis PH, Leira EC, Chang KC, Bendixen BH, Clarke WR, Woolson RF, Hansen MD. Baseline NIH Stroke Scale score strongly predicts outcome after stroke: A report of the Trial of Org 10172 in Acute Stroke Treatment (TOAST). Neurology. 1999 Jul 13;53(1):126-31. PubMed PMID: 10408548.Research PaperSchlegel D, Kolb SJ, Luciano JM, Tovar JM, Cucchiara BL, Liebeskind DS, Kasner SE. Utility of the NIH Stroke Scale as a predictor of hospital disposition. Stroke. 2003 Jan;34(1):134-7. PubMed PMID: 12511764.Research PaperRundek T, Mast H, Hartmann A, Boden-Albala B, Lennihan L, Lin IF, Paik MC, Sacco RL. Predictors of resource use after acute hospitalization: the Northern Manhattan Stroke Study. Neurology. 2000 Oct 24;55(8):1180-7. PubMed PMID: 11071497.Research PaperAppelros P, Terént A. Characteristics of the National Institute of Health Stroke Scale: results from a population-based stroke cohort at baseline and after one year. Cerebrovasc Dis. 2004;17(1):21-7. Epub 2003 Oct 3. PubMed PMID: 14530634.

    Other References

    Research PaperYoo AJ, Barak ER, Copen WA, Kamalian S, Gharai LR, Pervez MA, Schwamm LH, González RG, Schaefer PW. Combining acute diffusion-weighted imaging and mean transmit time lesion volumes with National Institutes of Health Stroke Scale Score improves the prediction of acute stroke outcome. Stroke. 2010 Aug;41(8):1728-35. doi: 10.1161/STROKEAHA.110.582874. Epub 2010 Jul 1. PubMed PMID: 20595665.Research PaperIntracerebral hemorrhage after intravenous t-PA therapy for ischemic stroke. The NINDS t-PA Stroke Study Group. Stroke. 1997 Nov;28(11):2109-18. PubMed PMID: 9368550.Research PaperBrott 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 Jul;20(7):864-70. PubMed PMID: 2749846.
    Dr. Patrick D. Lyden

    From the Creator

    Why did you develop the NIH stroke scale?
    The NIH stroke scale was developed for use in the NINDS tPA trial [demonstrating improved outcomes in ischemic stroke for patients receiving tPA].

    What pearls, pitfalls and/or tips do you have for users of the NIH stroke scale? Are there cases in which it has been applied, interpreted, or used inappropriately?
    The point of the NIHSS is to rate groups of patients, not individuals. This is fundamental and important for users to keep in mind. A lot of the scoring rules are counterintuitive if you’re a good neurologist. It’s not true that you have to be a neurologist in order to use the NIHSS. You have to use the scoring rules. Neurologists actually do the worst. ED physicians do the best, because they follow the rules. Neurologists think they’re smarter than the scale, so they don’t follow the scoring rules. The scoring rules are there to assure reproducibility, across users of all different backgrounds, whether it’s a neuro nurse, a neurologist, or an ED physician.

    The government is now looking at outcomes based on stroke severity, so all of a sudden, this scale that we invented for research has become essential for hospitals to get reimbursed, because the more severe the stroke is, the more the reimbursement. The stroke scale has grown so far beyond its original purpose, which is fine, but you have to understand where it came from and how to use it correctly.

    What recommendations do you have for health care providers once they have applied the NIH stroke scale?
    Higher stroke scale scores indicate higher severity and poorer prognosis, but the stroke scale is NOT a guide to picking patients for tPA. tPA should be used regardless of severity.

    How does the NIHSS compare to other stroke assessments?
    At the time the NIHSS was developed, there were a dozen other scales, and they’re all roughly the same. There’s only so many ways to put numbers on the neuro exam. But the NIHSS is the most widely used, because of its use in the tPA trial, and there are training videos available. It was adopted because it happened to be the scale that was used in the tPA trial. And since the tPA trial was the first positive stroke [treatment] study, everybody started using the NIHSS. So there are over 800,000 people worldwide who have been certified with those videos. It’s not inherently better than any other scale, but it’s used, and everybody knows it.

    Why did you modify the original NIHSS?
    The modified NIHSS is more reproducible than the original. We collapsed some items, and made some items easier to score, and the data show that it’s clearly more reproducible than the original. But it has not really been adopted.

    Why not?
    I think it’s just inertia. I think if people got familiar with the modified NIHSS, they would use it, but it was never part of a successful clinical trial, so it didn’t have the cachet of the original scale.

    About the Creator

    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. Previously, he was a professor and vice chairman for clinical neurology at UCSD and served as the Clinical Chief of Neurology and Director of the Stroke Center at UCSD Medical Center. Dr. Lyden has published more than 200 journal articles and abstracts and edited a textbook on stroke intervention.

    To view Dr. Patrick D. Lyden's publications, visit PubMed

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