Inclusion Criteria:  Focal epilepsy which is refractory (at least 2 different AEDs tried) and therefore has an indication for start of brivaracetam Age ≥ 18 years. IQ > 70 defined as any form of secondary education  Exclusion Criteria:  - Inclusion not possible within 2 weeks after start of brivaracetam History of a progressive cerebral disorder (neurodegenerative diseases, tumours) History of psychogenic nonepileptic seizures (PNES) Inability to provide informed consent Any contra-indication for brivaracetam Current or recent use (exposed ≤ 90 days) Current or recent use (exposed ≤ 90 days) of levetiracetam Current treatment with neurostimulation Inability of handling the tVNS device personally Subjects that have a current diagnosis of cardiac arrhythmic disease Any contraindication for tVNS: pregnancy, active implants (such as cardiac pacemakers of cochlear implants) or cerebral shunts (e.g. ventriculo-peritoneal shunts with valve) Any contraindication for MRI: metallic foreign body, pacemaker, claustrophobia, pregnancy