Biexponential diffusion alterations in the normal-appearing white matter of glioma patients might indicate the presence of global vasogenic edema

PurposeTo investigate normal-appearing white matter (NAWM) microstructure of glioma patients with biexponential diffusion analysis in order to reveal the nature of diffusion abnormalities and to assess whether they are region-specific or global. Materials and MethodsTwenty-four newly diagnosed glioma patients (grade II-IV) and 24 matched control subjects underwent diffusion-weighted imaging at 3T. Diffusion parameters were calculated using monoexponential and biexponential models. Apparent diffusion coefficient (ADC) values were measured in the entire NAWM of the hemisphere contralateral and ipsilateral to the tumor. In the contralateral NAWM, regional ADC values were assessed in the frontal, parietal, occipital, and temporal NAWM. ResultsADC(mono) and ADC(fast) were significantly higher than control values in all investigated regions except the temporal NAWM (P<0.04). ADC(slow) was significantly increased in the total contralateral, frontal, and parietal NAWM (P<0.03), while p(slow) was decreased in both total hemispheric NAWM and the parietal NAWM of glioma patients compared to controls (P<0.04). ADC(mono), ADC(fast), ADC(slow), and p(slow) were significantly different among the NAWM of the four lobes of the contralateral hemisphere in both groups (P<0.0001), and these regional differences were similar in patients and controls (P>0.05). Hemispheric ADC(mono) and p(slow) differences were different between groups (P<0.05). ConclusionGlobally altered diffusion parameters suggest the presence of global vasogenic edema in the NAWM of glioma patients, which is further supported by the finding that regional differences in patients follow those found in controls. Alternatively, some tumor infiltration might contribute to diffusion abnormalities in the NAWM, especially in the tumor-affected hemisphere. J. Magn. Reson. Imaging 2016;44:633-641.