The Children's Adaptive Deep Brain Stimulation for Epilepsy Trial

Children enrolled in this study must: * Be 5-14 years of age at consent. * Have a diagnosis of LGS, as determined by: * Slow (\<3.0Hz) spike-and-wave pattern and/or fast wave pattern (tonic seizures) detected on EEG at least six-months prior to the enrolment into the baseline period * History of drop seizures (tonic, atonic, or tonic-clonic) that precedes at least six-months prior to the enrolment into the baseline period * Have experienced at least 10 seizures in the four weeks prior to enrolment. * Have tried and not responded to two or more antiseizure medications prior to enrolment. * Be taking one or more anti-seizure medication(s) at a stable dose for at least the four weeks prior to enrolment. * Have a carer who is willing for their child's maintenance anti-seizure medications and ketogenic diet (if relevant) to be unaltered for the trial duration. * Have a carer who is willing and able to comply with all the requirements of the study, including the completion of the seizure diary and periodic device charging. Children enrolled in this study must not: * Have received prior deep brain stimulation insertion. * Have an active ('on') vagus nerve stimulator (or active within the six months prior to the baseline period). * Have had a change in their anti-seizure medication prescription or stopped their ketogenic diet within the last 4 weeks * Have started or made changes to the prescription of a ketogenic diet within the last 12-weeks * Have abnormal thalamic anatomy detected on imaging that would render DBS either unsafe or unfeasible. * Have a bleeding disorder(s). * Have a medical condition(s)/factor(s) that would increase their anaesthetic risk to an unacceptable level. * Have a nickel allergy. * Be pregnant.