The role of diffusion weighted magnetic resonance imaging in intracranial non-iscemic lesions

To define the diffusion-weighted resonance (MR) imaging findings in intracranial non-ischemic lesions and to investigate possible special features for the differential diagnosis. Seventy-one patients with intracranial non-ischemic lesions were included in the study. There were 19 arachnoid cysts, 2 epidermod cysts, 15 primary tumors, 9 metastases, 3 abscesses, 3 herpes encephalitis, 5 demyelinization, 3 tuberculosis meningitis, 2 bacterial encephalitis, 1 mumps encepahilitis, 5 non-specifik viral encepahilitis, 1 SSPE, 1 glutaric aciduria type-2. In all patients, echo-planar diffusion-weighted MR imaging was obtained in addition to conventional cranial MR imaging. The morphologic features of the cystic portion and the wall of the cyst and signal intensities on diffusion-weighted images were evaluated. All abscesses, epidermoid cysts, herpes encephalitis and 4 demyelinization lesions were hyperintense on diffusion-weighted images. 10 primary tumors, 5 metastases, 2 tuberculosis meningitis, bacterial meningitis, SSPE, Glutaric aciduria type 2, 2 non-specific viral encephalitis, mumps and bacterial encephalitis were hyperintense. All arachnoid cysts, 5 primary tumors and 4 metastases were hipointense on diffusion-weighted images. In primary tumors hyperintensity was seen due to hemorrhage or superinfection on diffusion-weighted images. This was a significant findings for the differentiation between tumor and abscess. Diffusion-weighted MR imaging is a useful technique for the evalution of the intracranial non-ischemic lesions and gives additional beneficial information to conventional MR imaging. However, misinterpretations for the tumor diagnosis due to hemorrhage and superinfection may occur. In this case, hyperintense appearance of tumor wall in contrast to abscess, which is iso-hypointense, may be useful for the differentiation.