Focal seizures despite three medicines in a 29-year-old

29-year-old right-handed woman with focal impaired-awareness seizures since the age of 17: a rising epigastric sensation, then staring, lip-smacking and fumbling with the right hand, 4–6 per month. Seizures continue despite adequate trials of levetiracetam, lamotrigine and lacosamide. 3 T epilepsy-protocol MRI is normal. Scalp video-EEG: interictal sharp waves and seizure onset over the left anterior temporal region. Referred by the epilepsy surgery programme for functional imaging.