Presurgical language mapping in bilingual children using transcranial magnetic stimulation: illustrative case

Abstract

Background: Presurgical mapping of eloquent cortex in young patients undergoing neurosurgery is critical but presents challenges unique to the pediatric population, including motion artifact, noncompliance, and sedation requirements. Furthermore, as bilingualism in children increases, functional mapping of more than one language is becoming increasingly critical. Transcranial magnetic stimulation (TMS), a noninvasive brain stimulation technique, is well suited to evaluate language areas in children since it does not require the patient to remain still during mapping.

Observations: A 13-year-old bilingual male with glioblastoma multiforme involving the left parietal lobe and deep occipital white matter underwent preoperative language mapping using magnetic resonance imaging-guided TMS. Language-specific cortices were successfully identified in both hemispheres. TMS findings aided in discussing with the family the risks of postsurgical deficits of tumor resection; postoperatively, the patient had intact bilingual speech and was referred for chemotherapy and radiation.

Lessons: The authors' findings add to the evolving case for preoperative dual language mapping in bilingual neurosurgical candidates. The authors illustrate the feasibility and utility of TMS as a noninvasive functional mapping tool in this child. TMS is safe, effective, and can be used for preoperative mapping of language cortex in bilingual children to aid in surgical planning and discussion with families.

Keywords: bilingual; brain tumor; language mapping; noninvasive; pediatric; transcranial magnetic stimulation.

FIG. 1.

Preoperative MRI showing T1 (left) and hyperintense T2 (right) mass (white arrows), subsequently identified as glioblastoma multiforme. The images are depicted in radiological convention.

FIG. 2.

Results of TMS of the left hemisphere in English (A) and Italian (B) and the right hemisphere in English (C) and Italian (D). Gray pegs indicate stimuli that did not cause a speech error, whereas red pegs indicate performance errors, yellow pegs indicate semantic errors, and white pegs indicate speech arrest.

FIG. 3.

English and Italian speech maps visualized together in the left (A) and right (B) hemispheres. Red pegs indicate errors in English, while yellow pegs indicate errors in Italian. Gray pegs indicate stimuli that did not cause any speech error. Although each language is represented within the same broad cortical regions in both hemispheres, some focal sites appear to be language-specific. English-specific sites are circled in red; TMS stimulation at these sites produced errors in English but not in Italian. Italian-specific sites are circled in yellow; TMS stimulation at these sites produced errors in Italian but not in English. Shared cortical areas, where TMS stimulation produced errors in both languages, are circled in orange.

FIG. 4.

Postoperative MRI in neurological convention in axial (A), sagittal (B), and coronal (C) views showing locations of TMS responses in English (red) and Italian (yellow) in relation to the resection cavity. The patient had no postoperative deficits in either language.