Objective: To report a large single centre experience of stereoelectoencephalography (SEEG) in children.

Materials and Methods: Retrospective cohort study of all SEEG cases undertaken at Great Ormond Street Hospital for Children between November 2014 and March 2019.

Results: Seventy-five consecutive SEEG cases were identified in 72 patients with age range 3-19 (median 10.8) years. Indications for SEEG included lesion negative MRI (32.0%), patients in whom there was a lesion but non-concordant non-invasive investigations (18.7%) or the borders of the lesion were not defined (17.3%), patients with multiple lesions (14.7%) and those who had experienced recurrence following prior surgical treatment (17.3%). Between 5-19 (median 12) electrodes were placed per procedure and 19 (25.3%) were bilateral implantations. Complications included single electrode dysfunction in 4 cases (5.3%), haemorrhage in 2 cases (2.7%, one requiring emergency craniotomy for evacuation and both of whom recovered fully in 3 months) and a non-compliant patient pulling out the majority of electrodes prior to recording (1.3%). The seizure onset zone (SOZ) was identified in 54 patients and either resection or radiofrequency thermocoagulation (posterior insular SOZ) was offered in 51 (in 2, a peri-rolandic focus was found and resection was declined by the carers based on risk and in 1, insular thermocoagulation was declined by the carers due to improvement in seizure control). To date, 47 of these patients have undergone 50 treatments, including 41 tailored resections, 8 thermocoagulation procedures and one laser ablation. In resective specimens, histology was non-diagnostic (36.6%), focal cortical dysplasia (31.7%), tuberous sclerosis (19.5%) or other (12.2%). At 1 year follow-up following resective surgery, 56.5% were seizure-free (Engel Class 1).

Conclusions: SEEG in children is a safe technique. With careful selection, high rates of seizure freedom can be attained even in children with difficult-to-localise focal epilepsy.