We believe this is not entirely true, at least concerning the early phase of ischemic stroke (within 4 hours from the onset of symptoms). It is our conviction that the earlier the recognition of initial parenchymal injury the better, considering the particular therapeutic advantages this may imply. In one of the above mentioned papers (1), MR and CT have been compared, yet the time interval between stroke and CT was 8 hours; MR was performed on average of 4 hours later, which might be a source of bias in favor of MR.

In the other paper (2), only MR data are reported; no distinction is made as to the site of the lesions, whether infra-or supratentorial. Among the patients examined within 4 hours of the stroke, only one out of 11 presented signal abnormalities on T2/WI and six presented morphologic changes on T1/WI. Such morphologic changes can also be documented by CT, which in addition would show cytotoxic edema as loss of distinction between white and gray matter and/or slight hypodensity involving cortex and deep structures, at least in the supratentorial regions (3). The usefulness of arterial enhancement, as reported by Yuh et al (2), needs further evaluation. According to our data, CT is able to detect the presence of initial parenchymal injury within 4 hours of ictus. We do not feel that the data reported in the two papers mentioned above prove the superiority of MR over CT in hyperacute cerebrovascular ischemia.