gms | German Medical Science

Objective: In adults, navigated transcranial magnetic stimulation (nTMS) has been established as routine preoperative examination method for brain tumours in motor or speech eloquent location. Until now, the feasibility of nTMS in children with brain tumours is unclear. We analysed the operation-strategy planning and counselling the patient/parents with enriched data by nTMS examination.

Methods: We examined 8 children (age 4–17) with different brain tumour entities (and one child with left hemispheric posthemorrhagic damage with chronic epilepsy) in presumed motor or language eloquent location by nTMS. A motor mapping was performed in all children to identify the motor cortex (and cortical seed areas to visualize the corticospinal tract). Depending on tumour location, 5 of 8 children also underwent nTMS language mapping (rTMS) to detect language-associated cortical areas. Consecutively, we used these areas in conjunction with DTI fiber tractography to visualize the individual language network. The childrens compliance was ensured by accurately adapting the stimulation intensity to individual comfortable levels.

Results: All mappings could be performed successfully without inducing relevant side effect. The motor cortex, the cortical areas with reproducibly induced speech errors and the relevant underlying fiber tracts could be visualized in all but one cases. In a 7-year old boy with marginal developmental retardation, nTMS language mapping could not be performed. After mapping, an examination report demonstrating the spatial relation between tumour and functional tissue, was integrated in surgical planning and neuronavigation. 7 patients were operated according to the surgical plan. No surgical complications and no unexpected neurological deterioration were observed. 1 patient showed postoperative visual field cuts which improved over time and 1 patient showed upper extremity dominated incomplete paresis after hemispherotomy.

Conclusion: nTMS and DTI fiber tracking was experienced as improved surgical planning for approach and extent of resection as well as for counselling of parents. nTMS navigated surgical procedure can be regarded as a beneficial adjunct for neurosurgical procedures in eloquent areas in pediatric population.