gms | German Medical Science

Objective: Eloquent brain has become more and more accessible to surgery. Awake craniotomy with cortical mapping, intraoperative neuromonitoring, functional and diffusion weighted MR-imaging facilitate surgical procedures within or contiguous to Wernicke’s and Broca’s area or the primary motor cortex. Nevertheless, the localization of a lesion within these areas frequently precludes gross tumor resection or complete resection of an epileptogenic focus. We want to demonstrate the rational use of functional imaging to extent resection during repeated, delayed surgery, taking advantage of neuronal remodeling capacities.

Method: Our patient is a 23-year-old woman with a history of tonic-clonic seizures with loss of conscience and an intraaxial tumor (Oligodendroglioma WHO II°) within the left primary and supplementary motor cortex first diagnosed 2008. Until 2013 no further seizures occurred under anticonvulsive medication. Then she suffered a grand-mal and the MRI showed an increase of tumor volume. The tumor was resected under local anesthesia, although complete resection could not be achieved due to repeated focal motor fits and deterioration of movement. She recovered completely and seizures improved. With a delay of 14 months seizures activity increased despite adequate medication. Functional MRI with speech-, finger tapping- and foot tapping paradigm and diffusion weighted imaging was repeated and correlated with FET-PET.

Results: FET-PET disclosed enhanced tracer uptake. Functional MRI showed a dorsal shift of motor functions during finger tapping into the postcentral gyrus. During a second procedure cortex stimulation confirmed the expected anatomic conditions. In the dorsal part of the tumor, stimulation provoked perioral dysaesthesia but no seizures or motor impairment. MRI revealed complete resection of the tumor parts showing increased amino acid uptake. No further seizures were witnessed. A slight sensory deficit persisted which did not impair quality of life.

Conclusions: The human brain possesses an immense, but hardly predictable capacity to reorganize. Functional MRI is often used to localize speech dominance or motor regions but has limited accuracy. Nevertheless modern imaging technologies provide the opportunity for visualizing functional remodeling and appear to be useful for scheduled multistep surgery when used in combination with intraoperative cortical mapping. This appears relevant for the therapy of low-grade gliomas and maybe even more so in epilepsy surgery.