Abstracts

Rationale: Stereo-EEG (sEEG) is a minimally invasive technique for intracranial monitoring using small depth electrodes secured to the skull with anchor bolts. Traditionally, sEEG has been reserved for older patients given concerns for adequate bone purchase of the anchor bolt in the thin skull of an infant. However, with new sEEG technology and technique modifications, younger patients less than 3 years old can be safely implanted. Here, we describe the safety, feasibility, technical considerations of sEEG in cohort of 15 patients under 3 years of age.

Methods: The clinical records of a consecutive cohort of 175 pediatric epilepsy patients who were considered for epilepsy surgery at Lucile Packard Children’s Hospital were retrospectively reviewed for sEEG placement between the dates of 2/5/14 – 12/31/23. We identified patients including and under 3 years old who underwent sEEG placement. Basic demographic information, seizure history, neurosurgical procedural notes, and postoperative seizure and outcome data were analyzed. We also analyzed data on usage of sEEG head frames, electrodes, bolt sizes, and skull thickness, as measured by the temporal squamous bone thickness on patients’ CT scan at time of surgery.

Results: We identified 15 patients (10 males) with a mean age of 2.2±0.4 years old (1.4-2.7 years) at the time of sEEG. The mean age at seizure onset was 0.6±0.5 years (range 0.1-1.6 years). Developmental delay was present in 60%. The most common etiology was tuber sclerosis complex (TSC) present in 73%. Phase I video EEG demonstrated a single focus onset in 53% and multifocal in 47%. MRI was abnormal in 80% and non-lesional in 20%. The most commonly used head frame for sEEG was the Infiniti frame (60%), followed by Mayfield and Leksell. Patients had an average of 19.1±4 depth electrodes placed (range: 10-26). Regions interrogated with depth electrodes included frontal (n=14 patients), temporal (n=12), insular (n=4), parietal (n=10), occipital (n=4), and cingulate (n=4). The average thickness of the patient’s skull was 2.8±0.7 mm (range: 1.9-3.8). The most common bolts sizes used for fixation of electrodes were 20 mm (77%) and 25 mm (11%) of all bolts placed. All patients underwent definitive surgical intervention at an average age of 2.4±0.4 years (range 1.4-2.9). Difficulty in securing bolts to the thin skull was often noted in operative reports (33%), but no patients had complications associated with sEEG monitoring. Most common surgeries performed were lesionectomy (40%) and laser ablation (40%). At a mean follow-up of 1.2±1.2 years (range 3 weeks-3.4 years), 33% of patients achieved seizure freedom and 20% achieved a favorable outcome. 27% patients required an increase in the number of ASMs and 27% decreased their number of ASMs.

Conclusions: sEEG is feasible and safe to use in children under 3 years old who require invasive intracranial monitoring for seizure onset zone localization. Technical considerations including head frame selection and bolt size used appear relevant to optimizing the safety profile in this patient cohort.

Funding: No relevant sources of funding.