Schröder J, Cheng B, Ebinger M, Köhrmann M, Wu O, Kang DW, et al. Validity of Acute Stroke Lesion Volume Estimation by Diffusion-Weighted Imaging-Alberta Stroke Program Early Computed Tomographic Score Depends on Lesion Location in 496 Patients With Middle Cerebral Artery Stroke. Stroke. 2014
A large area of diffusion restriction seen on a MRI scan is predictive of increased risk of symptomatic intracranial hemorrhage. The ASPECTS score has been extensively studied and is used in clinical practice to estimate early ischemic changes and define a malignant infarct in the anterior circulation on a non-contrast CT scan. The authors of this study aimed to utilize the DWI ASPECTS score similarly to establish ischemic volume and predict a malignant infarct with volume >100ml.
Clinical, demographic and imaging data was obtained from the PRE FLAIR study database that was a multicenter observational study of patients with acute ischemic stroke that underwent a MRI scan within 12 hours of symptom onset. Only patients with MCA infarction were included and a stroke neurologist scored DWI ASPECTS. DWI lesion volumes were calculated utilizing a developed software tool in three MCA territories- deep MCA, superficial MCA and both superficial and deep MCA territories. Correlations between DWI-ASPECTS, DWI lesion volume and NIHSS were calculated using Pearson’s correlation coefficient. Receivers operating characteristic (ROC) curves were generated to determine the optimal DWI-ASPECTS cut off point to characterize a DWI lesion volume≥100 ml.
A total of 496 patients were included in the final analysis, mean age was 66+/1- 15 years and 47% of patients were female. The DWI volume of superficial MCA stroke lesions was higher as compared to those with deep MCA strokes (21.2ml vs. 7.2ml) while there was no difference between the two groups on median ASPECTS score. There was a significant negative correlation between DWI-ASPECTS and DWI lesion volume for all patients (r=-0.78, p<0.0001) as well as the DWI-ASPECTS and initial NIHSS (r=-0.49, p<0.0001). The negative correlation was stronger for patients with superficial MCA lesions as well as combination of both superficial and deep MCA lesions. ASPECTS score <6 was a predictor of a malignant MCA infarct with volume >100ml with a low positive predictive value but a high negative predictive value.
While ASPECTS was a good predictor of infarct volume in the patients with superficial MCA lesions, DWI ASPECTS inaccurately estimated the deep MCA stroke volume. A wide range of lesion volumes was identified per ASPECTS score value. The question arises – will we be using the DWI ASPECTS score in clinical practice for thrombolysis? Current guidelines recommend utilizing the non-contrast CT and the CT ASPECTS score has been validated in this regard. Additionally is it time efficient to obtain an MRI and calculate a DWI ASPECTS? We need to take a look at several aspects before we come to a conclusion about the DWI ASPECTS score.