Abstract
A new magnetic resonance imaging (MRI) Trauma Study was commenced in April, 1995, so that any pathological changes of traumatic brain injuries could be indentified. In our study, fluid attenuated inversion recovery (FLAIR) images, and multishot echo planar imaging T2^*-weighted images (EPI T2^*-WI) were used in addition to conventional T1-weighted images, T2-weighted images and T2-weighted sagittal images. In this series we focused our attention on small parenchymatous lesion of a mild or moderate form of diffuse brain injury. These injuries are shown as high intensity areas on T2-weighted images (T2-high intensity lesions) but are not visualized in CT images. This series consisted of 29 patients who were diagnosed with diffuse brain injury and whose CT scans showed a Diffuse Injury I or II, according to the CT classification of Marshall et al. With Gennarelli's clinical classification, most of the patients were described as mild or moderate diffuse brain injury. Nineteen patients were studied in an acute or subacute stage. In all but 3 patients, small T2-high intensity lesions were found in the brain parenchyma. Susceptibility artifacts were displayed by an EPT T2^*-WI in 56% of the brain stem lesions, 69% of the corpus callosum lesions, and 91% of the supratentorial lesions. Elderly patients were excluded because of the possibility of age-related lesions. In the follow-up study brain edema was suggested because the lesions tended to be absent within 3 months in T2-weighted images and FLAIR. Susceptibility artifacts remained unchanged. In 10 patients examined during a chronic stage, susceptibility artifacts could be identified in most of the lesions initially shown as T2-high intensity lesions. Small hemorrhages in patients with Diffuse Injury II were shown with variable intensities on the conventional T1- and T2-weighted images, but were visualized with low intensity in an EPI T2^*-WI. In diffuse brain injuries, small T2-high intensity lesions have been considered to be brain edema or ischemic insults. Our data however, suggested that microhemorrhages associated with brain edema were present in most of the supratentorial lesions, and in more than a half of the lesions in the corpus callosum and the brain stem. These findings appear similar to contusions, which are defined as traumatic bruises of the neural parenchyma. The use of MRI has increased our understanding of in vivo pathological changes in mild or moderate forms of diffuse brain injury.
