Abnormalities in the normal appearing white matter of the cerebral hemisphere contralateral to a malignant brain tumor detected by diffusion tensor imaging.

INTRODUCTION: Malignant brain tumors tend to migration and invasion of surrounding brain tissue. Histopathological studies reported malignant cells in macroscopically unsuspicious parenchyma (normal appearing white matter - NAWM) remote from the tumor localization. In early stages, diffuse interneural infiltration with changes of the apparent diffusion coefficient (ADC) and fractional anisotropy (FA) is hypothesized. MATERIAL AND METHODS: Patients' ADC and FA values from NAWM of the hemisphere contralateral to a malignant glioma were compared to age- and sex-matched normal controls. RESULTS: Apparent diffusion coefficient levels of the entire contralateral hemisphere revealed a significant increase and a decrease of FA levels. An even more pronounced ADC increase was found in a region mirroring the glioma location. CONCLUSIONS: In patients with previously untreated anaplastic astrocytoma or glioblastoma, an increase of the ADC and a reduction of FA were found in the brain parenchyma of the hemisphere contralateral to the tumor localization. In the absence of visible MRI abnormalities, this may be an early indicator of microstructural changes of the NAWM attributed to malignant brain tumor.