gms | German Medical Science

Objective: Functional mapping techniques like fMRI and MR diffusion tensor tractography are increasingly integrated in neurosurgical procedures; however, so far only little experience is available in pediatric patients. We report first experiences from surgical procedures in which motor fMRI and MR-diffusion-tractography proved useful in the preservation of critical motor system and optical pathways.

Methods: 12 pediatric patients were meticulously prepared and analyzed using tractography and fMRI. Repetitive squeezing of the examiner’s hand during fMRI elicited activation in the “hand knob” area of the right pre- and postcentral gyrus, immediately anterior to the epileptogenic focus. Tractography identified the cortico-spinal tract, using seed regions in the pre- and postcentral gyrus and in the pons. Data processing was performed using iPlan 2.6 (BrainLaB), for both fMRI and tractography. Finally, the identified structures were exported for intra-operative neuronavigation. Intraoperative electrophysiological examinations were correlated.

Results: After craniotomy, neuronavigation confirmed the anatomically identifiable hand area to harbor the fMRI activation, and to be the origin of the cortico-spinal tract as defined by tractography. Careful resection immediately anterior to the course of the cortico-spinal tract allowed macroscopically complete tumor resection. Post-resectional cortical stimulation showed preserved MEPs. No additional deficits were ascertained. The preoperatively designed neuronavigational data were confirmed intraoperatively by cortical stimulation and by visually evoked potentials (VEP).

Conclusions: Pre-operative motor fMRI is feasible in pre-school children. The integration of these data, together with MR diffusion tractography, is highly valuable for resections in the vicinity of functionally critical structures. The technique presented allows the successful resection in cases previously classified as inoperable.