Neuroplastische Veränderungen im visuellen System bei Patienten mit Hirntumor in der radiatio optica

The influence of brain tumors along important structures of the visual pathway on the overall organization of the visual system is not yet well understood. To address this, the influence of a brain tumor in the area of the optic radiation on the functional connectivity of the visual network was investigated in this study.

fMRI data of 145 patients (76 male, 69 female, mean age 54.15 years) with brain tumors (96 left hemisphere, 49 right hemisphere) were included in this study. Based on the tumor location, patients were either assigned to a group with tumors in the area of the optic radiation (69 patients) or to a group that did not involve this structure (76 patients). A word generation task was chosen as fMRI paradigm, as this reliably addresses the visual system through the visual presentation of stimuli in written form. Based on these data, seed-to-voxel functional connectivity was calculated using the CONN toolbox. Here, four different Regions of Interest (ROIs) of the visual network were used as seed regions. These ROIs were located in the calcarine cortex of both hemispheres (CC), occipital poles of both hemispheres (OP), and lateral occipital cortex of each the left (LOCL) and right (LOCR) hemisphere.

The results showed that patients with tumors distant from the optic radiation had higher connectivity regarding all four ROIs compared to patients with tumors located in the projection area of the optic radiation. Significant connectivity clusters included parts of the left planum temporale, Heschl"s gyrus, parietal operulum, and central opercular cortex for the CC (p = .013), OP (p < .001), and LOCR (p < .001) seed ROIs. Also, the left lateral occipital cortex was included in the significant connectivity clusters of the OP and LOCR seeds, while the same area of the right hemisphere was significant for the LOCL ROI (p = .045). To evaluate hemispheric effects, the patients were additionally subdivided according to the tumor-affected hemisphere. The results yieled similar significant connectivity profiles as the entire patient sample, except that the cluster sizes of the single significant connectivity clusters were reduced.

This study showed differences between the two patient groups in functional connectivity within the visual network. The results suggest that not only primary visual areas but also higher visual areas appear to be affected, as significant voxels were not only found in the occipital lobe, but also in the parietal and temporal lobes.