Predicting Early Deterioration or Improvement in Ischemic Stroke by Transcranial Doppler
To the Editor:
I read with great interest the recent Stroke article by Toni and colleagues.1 In this study, early deterioration and early improvement were defined by a decrease or an increase, respectively, of 1 or more points in the Canadian Neurological Scale score from hospital admission to 48 hours after stroke onset. Among the baseline clinical characteristics, the findings from CT scans on admission, and the 6-hour transcranial Doppler (TCD) findings, only normal 6-hour TCD and abnormal 6-hour TCD were identified by logistic regression as the respective predictors of early improvement and deterioration.1 Regarding their findings and interpretations, I would like to make the following comments.
First, a change of one Canadian Neurological Scale score is liable to interobserver and intraobserver variability, even though the Canadian Neurological Scale has been rigorously tested for reliability, validity, and efficiency.2 I wonder whether Toni and colleagues have tried other definitions of improvement and deterioration, such as a change of 2 or more points in the Canadian Neurological Scale scores.
Second, Toni and colleagues1 correctly pointed out the technical limitation of TCD: a poor acoustic window in some patients. While TCD may be useful in the acute management of ischemic stroke, I would like to know the percentage of stroke patients who were found to have a poor acoustic window during the same period of the present study.
Third, Toni and colleagues interpreted a TCD change from asymmetry to no-flow between 24 and 48 hours after stroke onset as a possible indication of occlusion of the distal portion of the middle cerebral artery (MCA). I think the TCD change could also be caused by extrinsic compression onto the MCA from the developing cytotoxic edema, since the infarct was large enough to involve the whole MCA territory of that deteriorating patient.
Finally, early hypodensity on the baseline CT scans (see Table 2 of Toni et al1) appears to predict early improvement and deterioration with comparable predictive values, sensitivity, and specificity as the TCD changes (see my accompanying Table⇓ and Table 3 of Toni et al1). Thus, early hypodensity on the baseline CT scans predicts deterioration, and normal appearance on the baseline CT scans predicts improvement. As emphasized by Harold Adams, Jr, in his review article on treating ischemic stroke as an emergency,3 the first few hours after stroke onset is the golden time window for intervention, and so precious time should not be wasted in ancillary diagnostic tests aiming at determining the likely cause of stroke or the presence of an arterial occlusion. My interpretation of the data from Toni and colleagues1 is that neither TCD performed a few hours after stroke onset nor serial TCD examinations would add to the information which is already available from recognizing early cerebral infarction in the baseline CT scan.
- Copyright © 1998 by American Heart Association
Toni D, Fiorelli M, Zanette EM, Sacchetti ML, Salerno A, Argentino C, Solaro M, Fieschi C. Early spontaneous improvement and deterioration of ischemic stroke patients: a serial study with transcranial Doppler ultrasonography. Stroke.. 1998;29:1144–1148.
Boysen G, Brott T, Orgogozo JM, Côté R, Hachinski V, van Gijn J, Warlow CP, Candelise L. Stroke scores and scales. Cerebrovasc Dis.. 1992;2:239–247.
We thank Dr Cheung for his appreciation of our article and for the opportunity he gives us to clarify some points.
A change of 1 point in the Canadian Neurological Scale score is a valid indicator of clinical change.R1 Moreover, the definition of deterioration we adopted has already been used in a number of previous works,R2 which makes our results comparable to those of other groups.
Approximately 10% of TCD examinations were unsuccessful due to lack of temporal bone acoustic window, a percentage in line with that reported in the literature. It was not our aim to demonstrate that early TCD is better than CT in predicting the early clinical course, given the emphasis we placed on CT in our previous works.R3 R4 However, considering only patients in whom early TCD can be performed, the multivariate analysis selected TCD and not CT findings as independent predictors of the clinical course. On the other hand, TCD and CT provide complementary rather than redundant information. In an emergency setting, when CT results may be completely negative, knowing whether MCA stem or branches are occluded can definitely help clinicians make therapeutic decisions.
The serial TCD study was aimed at providing further insight into the “vascular” pathophysiology of different clinical courses. In particular, in our series progression of arterial occlusion could be ruled out as cause of clinical deterioration, while early spontaneous recanalization was detected in both deteriorating and improving patients. Finally, we believe that in the single case in which we observed a shift of the TCD signal from asymmetry to no-flow, many explanations can be hypothesized. However, the possibility that this might have been determined by an extrinsic compression on the MCA stem exerted by brain edema is not supported by evidence in the literature.
Côté R, Battista RN, Wolfson C, Boucher J, Adam J, Hachinski V. The Canadian Neurological Scale: validation and reliability assessment. Neurology.. 1989;39:638–643.
Toni D. Predictors of stroke deterioration. Cerebrovasc Dis. 1997;7(suppl 5):10–13.
Toni D, Fiorelli M, Bastianello S, Falcou A, Sacchetti ML, Ceschin V, Sette G, Argentino C. Acute ischemic strokes improving over the first 48 hours of onset: predictability, outcome and possible mechanisms: a comparison with early deteriorating strokes. Stroke.. 1997;22:10–14.