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Accurate presurgical mapping of language cortices is crucial for surgical planning and minimizing post-operative deficits, particularly in young children where both invasive and non-invasive imaging methods (magnetoencephalography and fMRI) have limited success. We examined whether TMS is a viable alternative since it can be performed in awake, cooperating children and is not precluded by patient movement.

Thirteen patients (9 right-handed, 8 male) aged between 5 and 6 years underwent TMS language mapping. Eight children with brain tumor, two with cortical dysplasia, and one each with hippocampal sclerosis, stroke, or normal MRI were studied. Language cortices were localized and hemispheric dominance determined by applying 5Hz TMS while patients performed a color-naming task.

The language cortices in temporal and frontal regions were successfully mapped in both hemispheres in 9 patients, with 2 patients showing left dominance, 2 right, and 5 bilateral. Increased bilateral representation in this cohort may reflect developing language networks and/or disease-induced reorganization. Mapping in one child was limited to the tumor hemisphere and in 3 others could not be completed due to task difficulty or TMS-induced discomfort.

We illustrate the utility of TMS in identifying atypical language organization, optimizing risk-benefit evaluation (as in the patient with left temporal glioma where finding of bilateral language representation increased confidence in recommending surgery), and improving outcome through more informed surgical planning (language was intact post-operatively in 5 patients who had surgery).

We demonstrate that TMS is a safe, reliable, and effective tool to map language cortices in young children.

presurgical mapping, language, pediatrics, epilepsy, neurosurgery, transcranial magnetic stimulation