P01.11.A MECHANISMS OF LANGUAGE PLASTICITY IN PATIENTS HARBORING LEFT HEMISPHERE GLIOMAS

Abstract

Abstract BACKGROUND Infiltrating gliomas are slow growing intrinsic brain lesions that have been shown to induce functional reorganization, although the mechanisms by which this occurs are not well understood. The present study examines glioma-induced neuroplasticity of language networks to investigate this phenomenon. MATERIAL AND METHODS 117 patients’ fMRI scans were analyzed from patients harboring gliomas whom completed 1-5 fMRI language tasks. Data was analyzed via two methods: cluster-based and cortical/subcortical mask-based. Right hemisphere gliomas (RHG) (n=40) were first analyzed to establish a reliable control group by determining statistically significant voxels across all five language tasks (LT), yielding a core conserved network. The language network induced by left hemisphere gliomas (LHG) (n=77) was then directly compared to the RHG language network to examine language plasticity. RESULTS LHG induced global reorganization of the canonical language network, including preserved homologous and novel left hemisphere (LH) and right hemisphere (RH) activation clusters. In each of the five LT, the LHG group showed activation of fewer total suprathreshold voxels in both the cluster (3 fewer clusters and 38,892 fewer active voxels/task) and mask-based (8 fewer active masks/task and 91,965 fewer active voxels/task) analyses while having a higher peak intensity (5.4 total increase in zmax) within the activated clusters. In addition, a generalized pattern of increased RH recruitment was seen in LHG patients, with 87% (137/157) of non-zero masks shifting their laterality index (LI) to the right hemisphere. These data suggest that the reorganized LHG-induced language network functions through less nodes along with a rightward shift of language lateralization. In addition, a subgroup analysis of frontal (n=16) and temporal (n=32) LHG revealed that frontal tumors promote increased RH activation relative to temporal tumors, with 94% (32/34) of non-zero masks shifting their LI to the RH compared to 68% (23/34), respectively. Frontal tumors also preferentially recruit the contralateral (RH) frontal lobe and ipsilateral (LH) temporal lobe, while temporal gliomas preferentially recruit the ipsilateral frontal lobe. CONCLUSION Infiltrating tumors within the left hemisphere promote language plasticity via consolidation of the classical LH language network along with recruitment of previously silent, novel language areas in the right and left hemispheres. This improved understanding of patterns of language plasticity may aid in more accurate pre-surgical risk stratification and counseling, therapeutic targeting for post-surgical recovery, and intelligent “pre-habilitation” strategies to maximize neuroplasticity prior to tumor resection.