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.
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.
- Copyright © 1998 by American Heart Association
Grotta JC, Alexandrov A. tPA-associated reperfusion after acute stroke demonstrated by SPECT. Stroke. 1998;29:429–432.
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.
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.
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.