(Stroke. 1995;26:816-821.)
© 1995 American Heart Association, Inc.
Articles |
From the Departments of Neurology (P.L., C.L.) and Nuclear Medicine (F.R., P. De C.) and the Biostatistics Center (J.J.), Mont-Godinne University Hospital (Medical School of the University of Louvain), Yvoir, Belgium.
Correspondence to Patrice Laloux, MD, Mont-Godinne University Hospital, B-5530 Yvoir, Belgium.
| Abstract |
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Methods We studied 55 consecutive patients with acute (<12 hours) carotid infarct within 36 hours of symptom onset with SPECT. Clinical presentation was assessed by the Canadian Neurological Scale and stroke subtypes. SPECT indices were the degree and size of hypoperfusion and crossed cerebellar diaschisis as assessed by a semiquantitative analysis. Outcome was evaluated by the functional status and mortality (Rankin Scale score at 1 month).
Results The Rankin Scale score correlated with the degree (r=.580; P<.00001) and size (r=.616; P<.00001) of hypoperfusion. The mean degree and size of hypoperfusion were significantly higher in patients with poor outcome. Crossed cerebellar diaschisis had no significant predictive value. Statistical analysis determined threshold values for the Canadian Neurological Scale score and the degree and size of hypoperfusion for the functional status and mortality. The degree and size of hypoperfusion had no higher performance than the Canadian Neurological Scale score. The negative predictive value was excellent for both clinical and SPECT indices. Multivariate analysis selected only the size of hypoperfusion as an independent predictor for the functional status (P=.004) and the Canadian Neurological Scale score for mortality (P=.009).
Conclusions SPECT performed within 36 hours of onset predicts clinical outcome, but different clinical and SPECT indices with threshold values should be chosen according to the relevant outcome end point.
Key Words: cerebral ischemia stroke assessment stroke outcome tomography, emission-computed
| Introduction |
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We have previously reported that single-photon emission computed tomography (SPECT), a noninvasive technique readily available to study regional cerebral blood flow in the acute stage, may help to categorize patients by stroke subtypes that have a different outcome profile.22 Several studies with different methodological and technical approaches have supported the predictive value of SPECT in stroke prognosis,7 11 13 17 23 24 25 26 27 whereas others have not been conclusive.28 29 30 31 32 All studies have included patients with cortical infarct, and only three of them7 13 17 were performed within 24 hours. Only one study compared the prognostic value of SPECT with clinical determinants,11 and none compared the different SPECT indices. Thus, the aim of our study was to assess and compare the prognostic value of stroke severity, stroke subtypes, crossed cerebellar diaschisis, and degree and size of hypoperfusion in predicting clinical outcome in a large group of consecutive patients with cortical and subcortical acute carotid infarct. After calculation of threshold values for each clinical and SPECT index, a multivariate analysis was performed to identify the predictive factors with an independent effect on outcome.
| Subjects and Methods |
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6.5,33 respectively. In addition, clinical stroke
subtypes as defined by Bamford et al9 were classified
according to presenting symptoms and signs at the time of maximum
deficit (lacunar infarcts: pure motor stroke, pure sensory stroke, pure
sensorimotor stroke, ataxic hemiparesis; total anterior circulation
infarcts: combination of new higher cerebral dysfunction [eg,
dysphasia, dyscalculia, visuospatial disorders], hemianopsia, and
ipsilateral motor and/or sensory deficit of at least two areas of the
face, arm, and leg [in cases of impaired consciousness and difficulty
in testing higher cerebral function or visual fields, a deficit was
assumed]; partial anterior circulation infarcts: combination of only
two of the three components of the total anterior circulation infarct
syndrome, with higher cerebral dysfunction alone or with a
motor/sensory deficit more restricted than those classified as lacunar
anterior circulation infarct [eg, confined to one limb or the face and
hand but not to the whole arm]). All patients received standard
treatment including hemodilution when hematocrit level was >45% and
anticoagulant in case of stroke in progression or cardiac-source
emboli. An initial brain CT without contrast (Siemens DRH) was performed in 34 patients within the first 24 hours with a mean time interval of 7 hours 24 minutes (range, 1 hour 54 minutes to 24 hours). A CT scan with contrast was obtained in 47 patients at least 48 hours after onset with a mean time interval of 8 days (range, 2 to 21 days). Contiguous axial slices (matrix of 512 pixels) were obtained parallel to the canthomeatal line. Slice thickness was 4 mm (scan time, 7 seconds per slice) in the posterior fossa and 8 mm (scan time, 5 seconds per slice) in the cerebral hemispheres. Acute or subacute cerebral infarct was defined by the presence of at least one of the following CT characteristics: focal hypodensity, mass effect on adjacent ventricles and cerebral sulci and fissures, and peripheral contrast enhancement.34 Topography of infarcts was classified according to the anatomic vascular territory.35 The definition of cortical and subcortical infarcts was the same as that used in a previous study.22 When control CT scan was normal or could not be performed, superficial or deep carotid localization was clinically defined by the presence of cortical signs (hemiplegia with predominant brachiofacial involvement, monoplegia, neuropsychological impairment) or clinical deficit compatible with a deep localization (subcortical aphasia, pure motor stroke, pure sensorimotor stroke, pure sensory stroke, ataxic hemiparesis), respectively. Although pure sensory stroke has been depicted mainly in thalamic infarcts, it has been also reported in cortical36 and capsular37 38 39 40 carotid infarcts. Consequently, patients with this syndrome were not excluded in our study.
SPECT using 99mTc-HMPAO (740 mBq; Ceretec, Amersham) was carried out with a rotating gamma camera (General Electric; 64 projections of 30 seconds each). Data were reconstructed to obtain consecutive axial slices every 12 mm parallel to and above the orbitomeatal line. Sixteen symmetrical regions of interest (ROIs) were considered, six over each cerebral hemisphere and two over each cerebellar hemisphere. With a computerized program developed in our laboratory, the ROIs (3x3 pixels; pixel size, 6 mm) were automatically located along the cortical ribbon, four in the anterior, middle, and posterior areas and four in the cerebellum. Because of the poor spatial resolution of our single-head gamma camera, ROIs were not placed in subcortical regions. The images in the inferior anterior temporal and high vertex cortical regions, as well as the cerebellum posteriorly, were excluded for analysis because of greater side-to-side variability.41 In each ROI, the difference in total count was expressed as a percentage of the value from the contralateral asymptomatic hemisphere with a normal cerebral blood flow. Interhemispheric difference of at least 10% was considered to be significant.41 42 For each patient, the degree of hypoperfusion was defined by the highest interhemispheric difference. We determined the size of hypoperfusion by the number of ROIs with an interhemispheric difference of at least 10% in the hemispheric slices selected for analysis as described above. Crossed cerebellar diaschisis was defined by the presence of at least 5% hypoperfusion43 44 in the cerebellar hemisphere contralateral to the hemispheric hypoperfusion. SPECT examinations took place within the first 36 hours in all patients with a mean time interval of 14 hours 54 minutes (range, 1 hour 4 minutes to 35 hours 38 minutes). SPECT was obtained within the first 24 hours in 45 (82%) patients.
Outcome evaluations were performed by neurologists blinded to SPECT data. Given that most patients in our tertiary-care hospital could not be systematically evaluated at 3 months, we studied only the short-term outcome at 1 month using the Rankin Scale.45 The outcome parameters were (1) the functional status derived from the Rankin Scale classification of patients with good (score of 1 to 3) or poor (score of 4 and 5) outcome and (2) mortality.
Numerical parameters were expressed as mean±SD and medians. Categorical and continuous variables were compared using Fisher's exact test and Wilcoxon rank sum test, respectively. Correlations between numerical parameters were assessed by Spearman's rank correlation coefficient. The performance of degree and size of hypoperfusion and CNS score for the different parameters of outcome was studied by receiver operating characteristic (ROC) methodology. ROC curves were fitted by maximum-likelihood estimation under the binomial model using the LABROC1 program, and areas under curves were compared by z test using the CLABROC program.46 ROC curves were used to define threshold values that maximized sensitivity plus specificity, and the performances of these newly defined dichotomous parameters for predicting outcome were assessed by sensitivity, specificity, and positive and negative predictive values. Logistic regression, with backward selection of variables using Wald's test performed with SPSS statistical software, was used to identify variables with an independent effect on outcome.
| Results |
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6.5, respectively. With regard to stroke subtypes, total
anterior circulation infarct was found in 18 (33%) patients, partial
anterior circulation infarct in 20 (36%), and lacunar anterior
circulation infarct in 17 (31%). At 1 month, 7 (13%) patients had a
poor outcome, and 41 (74%) had a good outcome. Seven (13%) patients
died, 5 of transtentorial herniation, 1 of bronchopneumonia, and 1 of
myocardial infarct. The overall CT sensitivity was 29% (10/34) within
24 hours after onset and 81% (38/47) after 48 hours. The topography of
infarcts was cortical in 55% (21/38) of patients and subcortical in
45% (17/38). Six (35%) of the 17 subcortical infarcts were lacunar,
representing 16% of all infarcts. SPECT showed a relevant
cerebral hypoperfusion in 37 (67%) patients. The mean degree and size
of hypoperfusion were 34±19% (range, 11% to 81%; median, 31%) and
8±6 (range, 1 to 26; median, 6), respectively. We noted crossed
cerebellar diaschisis in 12 (32%) patients with a mean degree of
hypoperfusion of 15±6% (range, 6% to 25%; median, 14%).
We found significant correlations between the Rankin Scale score and
the degree (r=.580; P<.00001) and size
(r=.616; P<.00001) of hypoperfusion (Table 1
). The mean degree and size of hypoperfusion were
higher in patients with poor outcome and in those who died early (Table 1
). The functional status was not dependent on age and sex ratio, but
mortality was significantly associated with higher age (77±4 versus
70±9; P=.045).
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The ROC curves for the degree and size of hypoperfusion and CNS score
as related to the different outcome parameters are shown in the
Figure
. To discriminate between the patients with good
or poor outcome, the threshold values derived from the ROC curves were
23.5% for the degree of hypoperfusion, 7.5 for the size of
hypoperfusion, and 5.0 for the CNS score. Similarly, the threshold
values were 21.5%, 3.5, and 5.0, respectively, to discriminate between
the patients who died or survived. In terms of area index, we found no
statistical difference between the degree and the size of
hypoperfusion, and neither had higher performance than the CNS score.
All results of SPECT and clinical indices in predicting the functional
status and survival are presented in Table 2
.
Crossed cerebellar diaschisis predicted survival but not functional
status; however, it did not reach statistical significance
(P=.067). Regarding clinical stroke subtypes on admission,
we found no significant difference in the outcome parameter between
lacunar and partial anterior circulation infarcts. On the other hand,
we noted significant differences between partial and total anterior
circulation infarcts in predicting functional status
(P<.001) and survival (P=.023). Significant
differences were also found between lacunar and total anterior
circulation infarcts for functional status (P=.001) and for
survival, even though statistical significance was not reached
(P=.064). All data regarding sensitivity, specificity,
positive and negative predictive values of the degree and size of
hypoperfusion, crossed cerebellar diaschisis, CNS score, and total
anterior circulation infarct stroke subtype to predict the different
parameters of outcome are shown in Table 3
.
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A multivariate analysis was performed to identify variables with an independent effect on outcome. The different variables studied were the degree and size of hypoperfusion, crossed cerebellar diaschisis, age, sex, CNS score, and stroke subtypes. The degree and size of hypoperfusion as well as the CNS score were considered as continuous values or as dichotomous variables according to the threshold value previously described for each parameter of outcome. Logistic regression selected only the size of hypoperfusion as a predictor of functional status (P=.004) and only the CNS score as a predictor of survival (P=.009).
| Discussion |
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In our study, the high sensitivity of SPECT (67%) compared with that of CT (29%) in the acute phase confirms its better prognostic potential. As did others,7 11 13 17 50 we found a strong correlation between cerebral blood flow measured by the degree and size of hypoperfusion and clinical outcome. As in other series,11 13 the mean degree and size of hypoperfusion permitted significant differentiation of patients for functional status and mortality. However, these results are of limited practical worth for the individual patient. Therefore, determination of threshold values is of great interest in predicting outcome in clinical practice. In a series of 32 cases, Giubilei et al13 determined a 40% threshold value of perfusion defect to discriminate between patients with a poor or good prognosis. Likewise, a threshold score combining the degree and size of hypoperfusion was reported by Hanson et al17 and Limburg et al7 in 15 and 26 patients, respectively. However, the performance of these cutoff levels has not been statistically calculated, and the number of patients was small. To our knowledge, no studies have assessed and compared by the statistical method of ROC curves the level of performance of clinical and SPECT indices in prognostic evaluation. Our study showed that the level of prediction performance of the degree and size of hypoperfusion and CNS score was excellent for functional status and intermediate for mortality, probably because of the small number of deaths in our series. Threshold values could be derived for the CNS score and the degree and size of hypoperfusion, but it must be stressed that these values were different according to the outcome parameters. As previously mentioned by Giubilei et al,13 these SPECT threshold values are in keeping with positron-emission tomography studies that also show a cerebral blood flow threshold below which outcome is poor60 because the cerebral tissue is no longer viable.61
Crossed cerebellar diaschisis, which has been shown to be related to infarct topography and size,62 could be considered as a potential predictive factor of outcome. We found that it could predict survival, but without reaching statistical significance, and that it was not predictive of functional status, contrary to other previous studies.53 63
Regarding stroke subtypes, our results are similar to those reported by Bamford et al9 in that total anterior circulation infarct was significantly associated with a worse prognosis than lacunar or partial anterior circulation infarct. However, the main drawback of this clinical classification in our study was the inability to find significant differences between lacunar and partial infarct to predict outcome.
Sensitivity and specificity of the different clinical and SPECT indices were excellent except for crossed cerebellar diaschisis, which showed a low sensitivity, particularly in predicting functional status. For mortality and functional status, the negative predictive value of different indices was very high, while the positive predictive value appeared to be low. In light of these results, these predictive values should be cautiously interpreted in clinical practice.
Logistic regression was performed to determine which clinical or SPECT indices could be considered independent predictive factors of outcome. The analysis selected only the CNS score for mortality and the size of hypoperfusion for functional status. Age, sex, and stroke subtypes were not selected. Thus, the threshold values of each of these independent predictive factors may be appropriately used in therapeutic trials to analyze separately those patients with mild defects who are likely to improve spontaneously and those with severe defects and poor outcome. As an example, according to our findings, subgroups of patients with poor (CNS score <6.5, size >7.5) or excellent (CNS score >6.5, size <7.5) outcome can be specified and evaluated separately.
In conclusion, SPECT performed within 24 hours may be helpful in predicting outcome in clinical practice and in appropriately categorizing patients into subgroups for therapeutic trials. Different clinical and SPECT indices should be chosen according to the relevant outcome end point.
| Acknowledgments |
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Received November 29, 1994; revision received January 16, 1995; accepted February 3, 1995.
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R. E. Latchaw, H. Yonas, G. J. Hunter, W. T.C. Yuh, T. Ueda, A. G. Sorensen, J. L. Sunshine, J. Biller, L. Wechsler, R. Higashida, et al. Guidelines and Recommendations for Perfusion Imaging in Cerebral Ischemia: A Scientific Statement for Healthcare Professionals by the Writing Group on Perfusion Imaging, From the Council on Cardiovascular Radiology of the American Heart Association Stroke, April 1, 2003; 34(4): 1084 - 1104. [Full Text] [PDF] |
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M. Takasawa, M. Watanabe, S. Yamamoto, T. Hoshi, T. Sasaki, K. Hashikawa, M. Matsumoto, and N. Kinoshita Prognostic Value of Subacute Crossed Cerebellar Diaschisis: Single-Photon Emission CT Study in Patients with Middle Cerebral Artery Territory Infarct AJNR Am. J. Neuroradiol., February 1, 2002; 23(2): 189 - 193. [Abstract] [Full Text] [PDF] |
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H. Barthel, S. Hesse, C. Dannenberg, A. Rossler, D. Schneider, W. H. Knapp, J. Dietrich, and J. Berrouschot Prospective Value of Perfusion and X-Ray Attenuation Imaging With Single-Photon Emission and Transmission Computed Tomography in Acute Cerebral Ischemia Stroke, July 1, 2001; 32(7): 1588 - 1597. [Abstract] [Full Text] [PDF] |
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T. Ueda, S. Sakaki, Y. Kumon, and S. Ohta Multivariable Analysis of Predictive Factors Related to Outcome at 6 Months After Intra-Arterial Thrombolysis for Acute Ischemic Stroke Stroke, November 1, 1999; 30 (11): 2360 - 2365. [Abstract] [Full Text] [PDF] |
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M. Weih, K. Kallenberg, A. Bergk, U. Dirnagl, L. Harms, K. D. Wernecke, and K. M. Einhaupl Attenuated Stroke Severity After Prodromal TIA : A Role for Ischemic Tolerance in the Brain? Stroke, September 1, 1999; 30(9): 1851 - 1854. [Abstract] [Full Text] [PDF] |
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J. Berrouschot, H. Barthel, R. von Kummer, W. H. Knapp, S. Hesse, and D. Schneider 99mTechnetium-Ethyl-Cysteinate-Dimer Single-Photon Emission CT Can Predict Fatal Ischemic Brain Edema Stroke, December 1, 1998; 29(12): 2556 - 2562. [Abstract] [Full Text] [PDF] |
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M. A. Meyer, J. Grotta, and A. Alexandrov Quantitative Brain SPECT and the NIH Stroke Scale • Response Stroke, July 1, 1998; 29(7): 1480 - 1480. [Full Text] |
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J. C. Grotta and A. V. Alexandrov tPA-Associated Reperfusion After Acute Stroke Demonstrated by SPECT Stroke, February 1, 1998; 29(2): 429 - 432. [Abstract] [Full Text] [PDF] |
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A. V. Alexandrov, J. C. Masdeu, M. D. Devous Sr, S. E. Black, and J. C. Grotta Brain Single-Photon Emission CT With HMPAO and Safety of Thrombolytic Therapy in Acute Ischemic Stroke : Proceedings of the Meeting of the SPECT Safe Thrombolysis Study Collaborators and the Members of the Brain Imaging Council of the Society of Nuclear Medicine Stroke, September 1, 1997; 28(9): 1830 - 1834. [Abstract] [Full Text] |
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S.E. Akopov, N.A. Simonian, and G.S. Grigorian Dynamics of Polymorphonuclear Leukocyte Accumulation in Acute Cerebral Infarction and Their Correlation With Brain Tissue Damage Stroke, October 1, 1996; 27(10): 1739 - 1743. [Abstract] [Full Text] |
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A. V. Alexandrov, S. E. Black, L. E. Ehrlich, C. F. Bladin, L. T. Smurawska, A. Pirisi, and C. B. Caldwell Simple Visual Analysis of Brain Perfusion on HMPAO SPECT Predicts Early Outcome in Acute Stroke Stroke, September 1, 1996; 27(9): 1537 - 1542. [Abstract] [Full Text] |
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