Diffusion anisotropy of the internal capsule and the corona radiata in association with stroke and tumors as measured by diffusion-weighted MR imaging

BACKGROUND AND PURPOSE: Diffusion-weighted MR images have enabled measureme nt of directionality of diffusion (anisotropy) in white matter. To investig ate differences in the anisotropy for various types of pathologic findings and the association between the anisotropy of tracts and neurologic dysfunc tion, we compared the anisotropy of the posterior limb of the internal caps ule and the corona radiata between patients with stroke and those with tumo rs and between patients with and without hemiparesis. METHODS: Thirty-three patients consisting of 11 with tumors and 22 with isc hemic disease (16 acute infarction, four old infarction, and two transient ischemic attack) and nine control patients were studied with a 1.5-T MR ima ger. Diffusion-weighted images were obtained with diffusion gradients appli ed in three orthogonal directions. The diffusion anisotropy measurements we re obtained from regions of interests defined within the internal capsule a nd the corona radiata, RESULTS: The diffusion anisotropy was significantly reduced in all internal capsules and coronae radiata involved by infarcts, tumors, and peritumoral edema compared with that of the control patients (P < .0001). This reducti on was most prominent in the tracts involved by tumors (P < .05), The aniso tropy of the internal capsules and coronae radiata was significantly decrea sed in cases with moderate-to-severe hemiparesis as compared with those wit h no or mild hemiparesis (P < .0001). Diffusion anisotropy tended to be als o reduced in normal-appearing internal capsules and coronae radiata that we re remote from the involved segment of the corticospinal tract. CONCLUSION: The degree of impaired diffusion anisotropy may vary in differe nt pathologic conditions and correlate with neurologic dysfunction, The mea surement of diffusion anisotropy may provide additional information relatin g to neurologic function and transneuronal effects.