(Stroke. 1998;29:1480.)
© 1998 American Heart Association, Inc.
Quantitative Brain SPECT and the NIH Stroke Scale
Michael A. Meyer, MD
Department of Neurology,
University of Missouri,
Columbia, Missouri
Key Words: stroke assessment • tomography, emission computed
To the Editor:
The excellent article by Grotta and Alexandrov1 not
only provides objective evidence in a small number of patients that
intravenous tissue plasminogen
activator (tPA) improves cerebral perfusion but also
provides important data about the National Institutes of Health Stroke
Scale (NIHSS) rating system. If the NIHSS score data from their article
are plotted against the corresponding single-photon emission computed
tomography (SPECT)-graded scale score, a relationship becomes apparent,
as shown in the
Figure
.
If one omits the 4 outlying points with high NIHSS scores with
less-than-expected asymmetries on SPECT in this group of 21 SPECT
scans, a fairly linear relationship is noted. Without these 4 pairs of
outlying data, approximately 10 points of deficit on the NIHSS roughly
correlates with 40 points on their SPECT-graded scale scoring system,
which quantifies the severity and extent of asymmetries in cerebral
perfusion over 4 SPECT slices.
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Figure 1. National Institutes of Health Stroke Scale (NIHSS) score data
from Grotta and Alexandrov1 plotted against the
corresponding single-photon emission computed tomography graded scale
(SGS) score.
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Rankin Scale scores at 1 month after stroke have been shown to
correlate with the degree and size of hypoperfusion on SPECT scans of
perfusion within 36 hours after symptom onset in a group of 55
patients.2 Whereas the baseline NIHSS score was found to
have an overall accuracy of 83% in predicting 3-month outcome in a
study of 373 acute stroke patients,3 more research is
needed on the predictive value of quantitative SPECT and how it
correlates with the NIHSS, Rankin Scale, and other functional outcome
measurements. A firm correlation remains to be made between NIHSS and
the degree and size of cerebral hypoperfusion in acute stroke; one or
more SPECT indices of volume and severity of hypoperfusion may need to
be considered.
References
1.
Grotta JC, Alexandrov A. tPA-associated
reperfusion after acute stroke demonstrated by SPECT.
Stroke. 1998;29:429–432.[Abstract/Free Full Text]
2.
LaLoux P, Richelle P, James J, DeCoster P, Laterre C.
Comparative correlations of HMPAO SPECT indices, neurologic
score, and stroke subtypes with clinical outcome in acute carotid
infarcts. Stroke. 1995;26:816–821.[Abstract/Free Full Text]
3.
Muir KW, Weir CJ, Murray GD, Povey C, Lees KR.
Comparison of neurological scales and scoring systems for acute
stroke prognosis. Stroke. 1996;27:1817–1820.[Abstract/Free Full Text]
Response
James Grotta, MD;
Andrei Alexandrov, MD
Stroke Program,
Department of Neurology,
University of Texas Health Science Center,
Houston, Texas
We thank Dr Meyer for his comments. We have also noted the
nice correlation between the neurological status of the patient on
arrival as measured by the baseline NIHSS and the perfusion defect as
measured by SPECT. In evaluating the acute stroke patient, we all want
a physiological test that is convenient, safe,
inexpensive, widely available, and informative. SPECT fulfills many of
these criteria. Perhaps clinical trials incorporating such studies will
show that these tests can help us select our therapeutic strategies.
However, until then, it is reassuring that in the first few hours after
stroke onset, the neurological exam accurately reflects what is going
on inside the brain physiologically.
