Abstracts

Rationale: The safety of TMS has been previously evaluated in healthy and clinical adult populations. We sought to fill the gap in safety of TMS functional mapping in a clinical, pediatric cohort.

Methods: In a retrospective chart review, we assessed 500 TMS studies (2012- mid 2020) in patients with epilepsy or brain tumor (Aged 0.16-64 years, 78% ≤18 years) for adverse events and safety of TMS in patients with cranial metal. Motor mapping was attempted in all, while language mapping was attempted in 305 patients.

Results: For almost all patients mapping was completed successfully; if pain at the stimulation site occurred, it was managed by reducing stimulation intensity. There were 92 patients with possible adverse events. Upon review, there were 6 patients who had a seizure prior to TMS stimulation and 4 patients with epilepsia partialis continua. These patients were not considered to have confirmed TMS-induced adverse events, and mapping was completed successfully. 82 patients (18.4%) experienced confirmed adverse events consisting of pain during stimulation (n=54) or seizure (n=28). Pain at the stimulation site during language mapping was the most common adverse effect comprising 10.8% of the total cohort, and mapping was discontinued due to persistent pain in 46 patients. In 7 sessions, the resting motor threshold could not be assessed due to pain at the stimulation site; however, in all 7 patients, the extent of the motor cortex was successfully mapped. One patient, under the age of one, did not complete successful motor mapping due to pain. 28 patients (6%) had seizures during or after TMS with semiology consistent with their typical presentation. 2 patients who had generalized tonic-clonic seizures required administration of rescue medications. 8 patients were unable to successfully complete the mapping during the same session due to their seizure but returned later to complete the mapping. Despite having seizures during mapping, the other 18 patients were able to complete mapping successfully. TMS was successfully completed in patients with cranial metal (n=276, 55.6%). 124 patients (44.9% of those with metal) had titanium screws and plates, with 2 patients having extensive titanium mesh; 73 patients (26.4%) had metal dental or facial work; 61 patients (22.2%) had Vagus nerve stimulators; 16 patients (5.8%) had ventriculoperitoneal shunts with 3 being programmable; 2 patients (0.7%) had intracranial metal, 1 patient with 4 encephalocele clips and 1 patient with 20 intracranial A coils.

Conclusions: Nearly 94% of patients with epilepsy or brain tumor were successfully mapped without experiencing a seizure during TMS. Moreover, the seizure events during/following TMS most likely are not directly attributable to the procedure, since all patients had refractory epilepsy with history of weekly/daily seizure frequency. We show that in this large mainly pediatric cohort with refractory epilepsy and brain tumor, TMS functional mapping is safe. We recommend the development of a standard protocol to record side effects for TMS patients, thus allowing for more complete characterization of adverse events and further improvement of the safety profile of clinical TMS.

Funding: Please list any funding that was received in support of this abstract.: N/A.