Medtronic Deep Brain Stimulation (DBS) Therapy for Epilepsy Post-Approval Study (EPAS)

Inclusion Criteria:

• Focal (partial) onset seizures (based on International League Against Epilepsy (ILAE) 2017 classification) that may or may not evolve to a bilateral tonic-clonicseizure (secondary generalization). The final determination shall be made by theInvestigator based on a clinical description of the seizures and previous diagnostictesting that includes, at a minimum, video EEG (inpatient or ambulatory) thatcaptured at least one ictal event

• Anticipated average of 6 or more focal (partial) onset seizures per month during CMMphase, with no more than 30 consecutive seizure-free days during the CMM phase

• Refractory to at least 3 antiepileptic drugs (AEDs) due to lack of effectiveness

• Age 18 or older at the time of enrollment

• Willing and able to complete the diary, with or without the assistance of acaregiver, in a reliable way as assessed by the clinical staff

• Able to use the Patient Programmer with or without the assistance of a caregiver

• Ability of the subject or legal representative to understand and provide signedconsent for participating in the study

• Willing and available to attend visits as scheduled and to comply with the studyprotocol

Exclusion Criteria:

• Generalized onset epilepsy type (based on International League Against Epilepsy (ILAE) 2017 classification)

• Seizure frequency is too frequent that subject is unable to provide daily count inorder to maintain a reliable seizure diary

• Any episode of convulsive status epilepticus within the 12 months prior to theEnrollment Visit

• Previous diagnosis of psychogenic/non-epileptic seizures within the 12 months priorto the Enrollment Visit

• Surgical candidate for and willing to undergo resective surgery

• Evidence of a neurological condition that is likely to progress (e.g., brain tumor,arteriovenous malformations or cavernous angiomas)

• Diagnosed with a progressive or degenerative neurological disorder affecting thebrain

• Significant medical condition that may impact study participation in the opinion ofthe investigator

• Presence of any of the following within 1 year prior to the Enrollment Visit:psychiatric illness hospitalization, suicide attempt or symptoms of psychosis (hallucinations, delusions) unrelated to an ictal state, a post-ictal state or amedication

• Malignancy or history of malignancy within 1 year prior to the Enrollment Visit (excluding resected basal cell carcinomas)

• Presence of implanted electrical stimulation medical device anywhere in the body (e.g., cardiac pacemakers, spinal cord stimulator, RNS) or any metallic implants inthe head (e.g., aneurysm clip, cochlear implant). In the case of an implanted vagusnerve stimulator (VNS), CMM study assessment collection may occur with the deviceimplanted but may not begin until the VNS has been off for at least 30 days. The VNSgenerator must be explanted prior to or at the time of the DBS neurostimulatorimplant and the leads removed or trimmed and capped. In the case of a subject whohad been previously implanted with a responsive neurostimulator (RNS) but had a fullsystem explant, a subject cannot begin CMM study assessment collection until the RNShas been off for at least 30 days.

• Risk factors that would put the participant at risk for intraoperative orpostoperative bleeding. This includes administration of any antiplatelet oranticoagulant medication in the 7 days prior to surgery, chronic anticoagulant use,chronic aspirin use of greater than 325 mg/day, and any participant with a historyof hemorrhagic stroke

• History of drug or alcohol abuse within the past year

• Condition or disease that is known to require repeat magnetic resonance imaging (MRIs)

• Currently participating, or plans to participate, in another investigational studyunless written approval is provided by the Medtronic study team

Implant Criteria

• Experienced an average of 6 or more focal (partial) onset seizures per month duringCMM phase, with no more than 30 consecutive seizure-free days (all seizure types)

• Completed a qualifying baseline diary. A qualifying baseline diary meets at leastone the following criteria: 1) a study diary with at least 28 completed days; 2) apre-existing diary with at least 70 completed days.

• Completed 3-month CMM visit

• No suicide attempt or other self-harm behaviors within past year (assessed byColumbia Suicide Severity Rating Scale (C-SSRS) at 3-month CMM Visit)

• For female subjects of child-bearing potential, has negative pregnancy test and ifsexually active continues using reliable form of birth control.