Posttraumatic edema in the corpus callosum shown by MRI.

MRI was performed on 120 patients who sustained closed head injury of varying severity. Patients ranged in age from 4 to 87 years (average, 32 years). All patients had an initial MRI within 28 days (median 12 days) of injury. MRI disclosed areas of abnormal signals in the corpus callosum of 21 (18%) of the 120 patients; 1 (2%) of the 44 patients who sustained mild injuries (GCS > or = 13), 3 (10%) of the 31 moderate injuries (GCS 9-12), and 17 (38%) of the 45 severe injuries (GCS < or = 8) (p < 0.0001). All but 2 of the 21 patients with corpus callosum lesions had other parenchymal lesions that were visualized by MRI. Of these 21 patients, MRI was repeated in 19. In 13 of the 19 patients, repeat MRI scans at 25 to 42 days after injury showed the disappearance of lesions that had on the first MRI shown a high signal on T2-weighted and FLAIR images and a normal signal on T1-weighted images. The MRI findings and time source of the disappearance of the corpus callosum lesions mirrored those of paracontusional edema in the subcortical white matter. Patients in whom the corpus callosum lesion disappeared had a better outcome than those in whom the lesion remained (good recovery/moderate disability; 92% vs 63%). The present MRI results suggest that some lesions in the corpus callosum following closed head injury are reversible, thus resembling edema that may be produced by a relatively mild shear strain force to the corpus callosum.