The UK experience of stereoelectroencephalography in children: An analysis of factors predicting the identification of a seizure onset zone and subsequent seizure freedom

ImportanceStereoelectroencephalography (SEEG) is more frequently being used in the pre-surgical evaluation of children with focal epilepsy. Many factors affect the rate of identification of a definable seizure onset zone (SOZ) and subsequent seizure freedom following SEEG-guided epilepsy surgery, which have not been systematically examined in multi-centre studies. ObjectivesDetermine the rates and factors that predict (a) whether or not a definable putative SOZ was identified on SEEG and (b) subsequent seizure freedom following surgical intervention. DesignRetrospective cohort study SettingMulticentre study involving 6 of 7 UK Childrens Epilepsy Surgery Service centres that perform paediatric SEEG in the UK. ParticipantsAll children undergoing SEEG from 2014 - March 2019 were included. Demographic, non-invasive evaluation, SEEG and operative factors were collected retrospectively from patient records. Main OutcomesThe two main outcome measures were (a) whether or not a definable putative SOZ was identified on SEEG (binary yes/no outcome) and (b) subsequent seizure freedom following surgical intervention (Engel classification) FindingsOne hundred and thirty-five patients underwent 139 SEEG explorations using a total of 1767 electrodes. A definable SOZ was identified in 117 patients (85.7%); odds of successfully finding a SOZ were 6.4x greater for non-motor seizures compared to motor seizures (p=0.02) and 3.6x more if [≥] 4 seizures were recorded during SEEG (p=0.03). Of 100 patients undergoing surgical treatment, 47 (47.0%) had an Engel class I outcome at a median follow-up of 1.3 years; the only factor associated with outcome was indication for SEEG (p=0.03). SEEG was safe with one (0.7%) haematoma requiring surgical evacuation and no long-term neurological deficits as a result of the procedure. Conclusions and RelevanceThis large nationally representative cohort illustrates that, in these patients who may not have otherwise been offered resective surgery, SEEG-guided surgery can still achieve high rates of seizure freedom. Seizure semiology and the number of seizures recorded during SEEG are important factors in the identification of a definable SOZ and the indication for SEEG is an important factor in post-operative outcomes.