Non-interventional Study Describing Healthcare Resource Utilisation and Clinical Outcomes Associated With VNS Therapy in UK.

Inclusion Criteria: Living subjects who meet all of the following criteria will be considered for enrolment: * Clinical diagnosis of drug resistant epilepsy * Subjects who have had their first VNS device (Demipulse®/Aspire HC®, Aspire SR® and SenTiva®) implanted at least 18 months prior to their enrolment in the study data (with no change in generator, battery or lead). * For SenTiva® and Aspire SR®, AutoStim was first activated within 1 month of implantation. * For SenTiva®, scheduled dosing mode was activated within 1 month of implantation. * Subjects must be able and willing to provide informed consent; subjects aged 7-12 years old and 13-15 years old will be provided with appropriate information and consent forms to explain the study in age appropriate language. These subjects will be asked to provide their assent to take part in the study, with consent provided by their parent/carer. Subjects under 7 years will be included in the study with consent from their parent/carer. For adult subjects (≥16 years) lacking the mental capacity to consent, advice about participation will be sought from an appropriate consultee, according to the Mental Capacity Act 2005. * Adult and paediatric subjects (aged over 2.5 years at study enrolment) with available medical records for at least 12 months prior to VNS device implantation. Exclusion Criteria: * Subjects whose medical records are not available for review. * Deceased subjects.