http://nho.sagepub.com/content/6/3/95?etoc
- James E. Siegler, Department of Neurology, Hospital of the University of Pennsylvania, 3400 Spruce St, 3 W Gates, Philadelphia, PA 19104, USA. Email: james.siegler@uphs.upenn.edu
In the most recent edition of The Neurohospitalist,
Marsh and colleagues reported a significant limitation of serial
National Institutes of Health Stroke Scale (NIHSS) assessments
in patients with acute ischemic stroke.1
The investigators rightfully concluded that an improvement in 4 points
on the NIHSS was less sensitive for detecting neurologic
recovery when compared to a comprehensive neurologic
examination. Recognition of this weakness is pertinent to all clinicians
who rely on the NIHSS to identify neurologic recovery
(or worsening), especially when using a prethresholded NIHSS improvement
in the definition of recovery.
The NIHSS is certainly not a replacement for a
full neurologic examination. This tool, however, has traditionally been
utilized
to quantitate neurologic change in patients with
stroke and serves as a useful adjunct in clinical decision-making and
for
research purposes. In some of the earliest clinical
trials using serial NIHSS assessments, a clinically significant change
has been prespecified at the same 4-point minimum as
in this study.2
This is reasonable given the (1) imperfect interrater reliability and
(2) fluctuations in neurologic symptoms depending on
patient alertness and time of day, which may render a
2-point threshold less specific. However, in my experience, a 2-point
threshold may be more sensitive and maintain a high
specificity when compared to these historic 4-point cutoffs.3 As the authors demonstrate,1
a 2-point improvement actually confers nearly identical prognostic
information regarding improvement when compared to the
comprehensive neurologic assessment. It may even
overestimate the degree of improvement. Specifically, at 24 hours
post-tissue
plasminogen activator, 78% of patients improved by ≥2
points compared to 71% who improved according to non-NIHSS neurologic
assessment. At discharge, this rose to 83% and 71%,
respectively, and at ∼1-month follow-up, 100% and 95%, respectively.
Therefore,
a 2-point threshold may perhaps be superior for
quantitating improvement in this population when compared to the 4-point
cutoff.
That being said, should the primary outcome of investigations such as these be improvement? The authors conclude that serial
NIHSS assessments are inadequate for capturing changes in functional outcome when in fact their findings indicate inadequately captured improvement.
The delivery of positive prognostic information to patients should
certainly be pursued and explored with research efforts,
but (as the authors affirm) serial NIHSS assessments
may be most relevant when “considering functional decline.”1 In my experience3 and others,4
serial NIHSS assessments can successfully capture deterioration.
Confirmatory research is called upon to determine whether
prethresholded NIHSS changes can be implemented
clinically to determine when it is appropriate to intervene and where it
may
be effective in identifying reversible causes of
deterioration.
The NIHSS is not an ideal tool for detecting
neurologic change after stroke. But a quantitative assessment should be
implemented
as an adjunct to the physical examination in order to
monitor for progression. For the time being, I find it reasonable to
perform serial NIHSS assessments in order to detect
neurologic deterioration—especially when a lower threshold (eg, 2- vs
4-point worsening) is used to detect a clinically
meaningful decline.5
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