gms | German Medical Science

Objective: Histological data of glioma patients provide evidence of tumor cell infiltration even in tumor distant brain regions, which is not delineated by conventional MRI. Diffusion tensor imaging (DTI) allows quantitative assessment of water diffusion, providing indirect information about white-matter integrity. As gliomas infiltrate along white matter fibres, we applied DTI to investigate structural integrity of normal appearing white-matter of extratumoral brain regions, and examined whether DTI measures relation to cognitive functions.

Methods: 15 cerebral glioma patients (mean age 44.9±14.6 yrs; 10 male; 1 left-handed; 8 right hemispheric; mean tumor volume 56.6±64,3 ml; 5 low & 10 high-grade), as well as 15 age-, sex-, handedness and education-wise matched healthy controls were preoperatively enrolled into the study. Subjects underwent conventional MRI and DTI, as well as a standardized neuropsychological examination including the verbal learning and memory task (VLMT). Tumor volumes were segmented on conventional MR-images, and tumor masks applied in order to restrict DTI-analyses to extratumoral brain regions, both in patients and matched controls. DTI-data was skeletonized using tract-based spatial statistics, and voxel-based mean diffusivity (MD) determined within this skeleton for each individual. MD-values were subjected to a histogram analysis, and the peak-width of skeletonized mean diffusivity (PSMD) was determined by calculating the difference between the 95th and 5th percentiles of the voxel-based MD-values within the skeleton. PSMD and behavioral performance were compared between patients and controls and correlated to behavioral parameters.

Results: PSMD of extratumoral white-matter negatively correlated with performance in encoding and verbal recall in patients (p<0.047) and controls (p<0.032). While behavioral performance differed not significantly between groups, comparison of PSMD revealed a trend towards higher PSMD values in patients (3.09 x 10-4 mm2/s) as compared to healthy controls (2.67 x 10-4 mm2/s) (p<0.078), with higher PSMD-values indicating structural disintegration.

Conclusion: DTI data suggested subclinical structural disintegration in extratumoral white-matter in glioma patients. Larger patient studies are needed to determine the pathophysiological relevance of DTI measures in tumor distant brain areas.