Adv Neurosciences Tech Le Bonheur Children's Hospital Neuroscience Institute
Rationale: Noninvasive functional brain mapping is critical in children with epilepsy, brain tumors, and other neurological conditions that may require surgical intervention. Procedures such as functional MRI (fMRI) and transcranial magnetic stimulation (TMS) can localize crucial language cortices of the brain and assist in neurosurgical planning. Use of these procedures may allow neurosurgeons to forego riskier invasive procedures, such as direct cortical stimulation (DCS), which is associated with increased risk of complications (Sweet, Epilepsia 2013;54(9):66-71). However, noninvasive language mapping in children can be challenging. fMRI requires the patient to remain still for extended periods of time, such that in many school-age children, procedural anesthesia is necessary. Successful language mapping in fMRI can be impeded by such sedation (Guerin, Semin Pediatr Neurol 2020). TMS, on the other hand, is not affected by patient movement and is performed without sedation (Narayana, Oper Neurosurg 2020;18(5):E175-E180). Therefore, we hypothesized TMS could be used to map language cortices in cases where sedate fMRI could not. Methods: We retrospectively reviewed our database and found 138 children, aged 5.1 to 19.4 years, who underwent both TMS and fMRI language mapping to assess success rates, sedation effects, and the viability of TMS, particularly as an alternative to fMRI where fMRI is impeded by sedation. Success was defined as clear, statistically significant determination of hemispheric language dominance for each procedure. Results: Of the 138 cases, TMS succeeded in determining language dominance in 118 (85.5%), aged 5.13 to 19.40 years. Of the 91 nonsedate fMRIs, 73 were successful (80.2%), while of the 47 sedate fMRIs, 12 were successful (25.5%). The age of sedated patients ranged from 5.1 to 18.4 years, with the majority under 10 (n=24) or 10 to 13 years (n=14). Furthermore, of the 35 failed sedate fMRIs, 30 were successfully mapped using TMS, with ages ranging from 5.13 to 18.40 years (mean 10.55±7.85). The remaining 5 cases, representing unsuccessful sedate fMRI and TMS, were aged 6.87 to 11.99 years (mean 9.81±2.9). Conclusions: These data illustrate the efficacy of TMS as an alternative to sedate fMRI for language mapping in children, particularly those aged five to 13 years. While nonsedate fMRI has a similar rate of success to TMS (80.2% vs. 85.5%), the difficulty of successfully mapping language cortices in fMRI with sedation is drastically decreased to a success rate of 25.5%. However, in the majority of cases (84.7%) where sedate fMRI was unsuccessful, TMS was able to successfully complete language localization and determine hemispheric language dominance. Because TMS is not precluded by patient movement during the procedure, it can be used effectively without sedation even in young children. Therefore, TMS should be considered as a viable alternative to fMRI for language localization in patients requiring fMRI sedation. Funding: Please list any funding that was received in support of this abstract.: N/A
