J Stroke Cerebrovasc Dis. 2013 Jul;22(5):675-82.

What change in the National Institutes of Health Stroke Scale should define neurologic deterioration in acute ischemic stroke?

Siegler JE, Boehme AK, Kumar AD, Gillette MA, Albright KC, Martin-Schild S.

Stroke Program, Department of Neurology, Tulane University Hospital, New Orleans, Louisiana, USA.

 

ABSTRACT

Background: Neurologic deterioration (ND) occurs in one-third of patients with stroke. However, the true incidence of ND and risk for adverse outcomes remains unknown because no standardized definition of ND exists. Our study compared the prognostic value of a range of definitions for ND in patients with acute ischemic stroke (AIS). Methods: All patients who presented to our center with AIS within 48 hours of symptom onset between July 2008 and June 2010 were retrospectively identified. Patient demographics, National Institutes of Health Stroke Scale (NIHSS) scores, etiologies of ND, and outcome measures were compared between patients according to a range of ND definitions using receiver operating characteristic analyses. Results: Three hundred forty-seven patients were included. The 2 definitions of ND with the highest sensitivity and specificity for several outcome measures were tested against each other: an increase in the NIHSS score by 2 or 4 points in a 24-hour period. More than one third (36.9%) of patients experienced 2-point ND versus 17.3% with 4-point ND. Patients who experienced ND by either definition had prolonged hospitalization (P < .001), poorer functional outcome (discharge modified Rankin Scale score > 2; P < .001), and higher discharge NIHSS score (P <.001) compared to patients without ND. Compared to patients without ND, a 2-point ND was associated with a 3-fold risk of death (odds ratio 3.120; 95% confidence interval 1.231-7.905; P = .0165) after adjusting for admission NIHSS score, serum, glucose, and age. Conclusions: A 2-point ND is a sensitive indicator of poor outcome and in-hospital mortality. An accepted definition of ND is needed to systematically study and compare results across trials for ND in patients with stroke.

Copyright © 2013 National Stroke Association. Published by Elsevier Inc.

PMID: 22727922

 

SUPPLEMENTARY

The study by Siegler et al. sought to determine a quantitative, prognostically useful definition for neurologic deterioration after acute ischemic stroke. The mechanism behind this deleterious process is likely multifactorial and involves compromise of the ischemic penumbra with spreading of infarction and progression of clinical symptoms.  Currently, there are numerous definitions for this multifactorial process which can occur in one-third of patients who suffer from stroke, and no standardized definition has been agreed upon.  Most centers in the United States and across the globe utilize the National Institutes of Health Stroke Scale (NIHSS) score to quantify the magnitude and severity of neurologic impairment following stroke. This scoring system, a 42-point assessment of neurologic function, was originally designed for the purpose of determining eligible candidates for thrombolytic therapy based on likelihood of functional recovery after treatment.  However, now the NIHSS is becoming more useful for trending the progression or improvement of neurologic symptoms after stroke.

In an attempt to identify the optimal threshold for a change in NIHSS which is most sensitive and specific for poor functional outcome, the authors of the present study compared several thresholds for NIHSS change against one another.  We chose a time frame of 24 hours between NIHSS score assignments (as opposed to longer time frames such as several days to weeks) because at our center, clinicians perform daily NIHSS examinations on stroke patients in order to trend recovery over time.  The use of a shorter period between NIHSS assessments, such as this 24 hour window, may also be an effective time to implement any appropriate clinical work up in the event of an episode of neurologic deterioration—which we have studied in subsequent clinical investigations.

Thresholds of 2-, 3-, 4-, 5-, and 6-point increases in the NIHSS were compared using receiver operating characteristic curves for sensitivity and specificity of predicting poor functional outcome.  A 4-point or more increase in NIHSS over 24 hours was found to be highly specific for unfavorable discharge disposition, poor functional outcome, and in-hospital mortality whereas a 2-point or more increase in NIHSS was generally more sensitive for these measures.  Therefore, the authors concluded that a 2-point change in the NIHSS over 24 hours was sufficient for diagnosing an episode of neurologic deterioration because of the associated poor prognosis.

In the future, we plan to study whether intervention for a 2-point increase in NIHSS may improve outcome in these patients at risk for a poorer prognosis following acute ischemic stroke.

 

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