Lesions of the Corpus Callosum

T his article reviews the causes and imaging appearances of lesions involving the corpus callosum (Table 1). The corpus callosum consists of densely bundled white matter tracts connecting the two cerebral hemispheres, with a compact structure that largely blocks interstitial edema and tumor spread. Isolated lesions of the corpus callosum are rare and may represent transient responses to injury or myelination abnormalities. More common butterfly lesions involve the corpus callosum and both cerebral hemispheres—a pattern associated with aggressive tumors, demyelination, and traumatic brain injury. Unenhanced CT is a first-line neuroimaging modality. Although soft-tissue contrast enhancement is limited, CT can help characterize hemorrhage, edema, mass effect, calcification, and necrosis. MRI provides more detailed information regarding tissue structure and composition, using various pulse excitation sequences, such as FLAIR, to distinguish abnormal signal in the corpus callosum from adjacent CSF in the lateral ventricles. Administration of IV contrast material is useful for characterization of neoplastic and vascular lesions, which may show characteristic patterns of enhancement.