gms | German Medical Science

Objective: Preoperative functional imaging is a useful tool to avoid neurological dysfunction caused by surgery. Furthermore it may show reorganisation, which has occured. Thus functional neuronavigation enables more radical tumor removal.

Methods: MEG measurements were carried out with a 2x37 channel biomagnetic system (Magnes II, 4-D Neuroimaging). Localization was performed by 1-dipole fit or beamformer algorithm. For fMRI we used a 1.5T MR scanner with echo planar imaging (Sonata, Siemens Medical Solutions) and a block paradigm with 180 measurements in 6 blocks (rest alternating with activation, 25 slices, 3 mm thickness & resolution TR=2470, TE=60). After surgery measurements with the same paradigms were performed and the results for certain cortex areas compaired in both hemispheres. Preoperative measurements of language functions were done in 283 patients and of motor functions in 217 patients. In 16 Patients we measured additionally postoperatively language functions and in 3 motor functions.

Results: In 7 of 16 patients language reorganisation was observed by comparing pre and postoperative measurements. In one of them we observed a shift of all language areas to homotopic areas of the contralateral hemisphere. In the remaining 6 patients only part of the language areas shifted to homotopic areas of the contralateral hemisphere. Activity in the original areas continued in all but one patient. In one patient a second surgery took place after 5 years. In spite of closer resection to the language area, she did not have language disturbances the second time contrary to the first surgery. In 3 patients we found reorganisation of motor functions. When using FMRI we observed, that postoperative measurement should be done not earlier than 3 month after surgery, because of BOLD effect disturbances.

Conclusions: Reorganisation of brain function due to lesion and surgery can be observed quite often. This shift of function can at least partially explain some maintained or regained function, if resection extends into eloquent cortex.