Etiology of Corpus Callosum Lesions with Restricted Diffusion

Infarction of the corpus callosum is rare, and other conditions can cause magnetic resonance imaging (MRI) restricted diffusion in the callosum, leading to diagnostic uncertainty. We sought to characterize the etiology of lesions with diffusion restriction in the corpus callosum.

Callosal lesions with restricted diffusion were identified at our institution between January 2000 and December 2010. Radiographic and clinical data were reviewed to determine whether the lesion was vascular and if so, to identify the underlying mechanism.

A total of 174 cases were reviewed in depth; 47 % were vascular and 53 % were nonvascular. Among vascular cases, atypical mechanisms of stroke (e.g., vasculitis/vasculopathy, hypercoagulable state) were most common (37 %), followed by cardioembolism (28 %). Vascular splenial lesions in particular were likely due to atypical causes of stroke. The most common nonvascular etiologies were trauma (44 %), tumor (22 %), and demyelination (15 %). Vascular lesions were more common in older, non-Caucasian patients with vascular risk factors. Nonvascular lesions were more likely to be found in association with T2-hyperintense cortical lesions, focal intraparenchymal enhancement, or edema/mass effect on MRI.

More than half of lesions with diffusion restriction in the corpus callosum are due to a nonvascular cause. Clinical and radiographic characteristics can help distinguish vascular from nonvascular lesions in the corpus callosum. Nonvascular lesions are more likely to be seen in younger patients without vascular risk factors and are more often accompanied by enhancement and edema. Vascular lesions are most commonly due to atypical stroke etiologies, and these patients may require additional diagnostic testing.