A 24-year-old woman is seen for a follow-up evaluation of epilepsy first diagnosed 4 years ago. The patient has five or six simple or complex partial seizures annually that have been difficult to control. The epilepsy was first treated with lamotrigine, to which levetiracetam was added 2 years ago. Although both medications decreased the frequency and intensity of the seizures when initiated, the episodes returned to their former state after several months. She cannot drive because the seizures often cause loss of consciousness. She has a history of febrile seizure as an infant. She otherwise has no significant medical history, and her only medications are lamotrigine, levetiracetam, and folic acid.
All physical examination findings are within normal limits.
An MRI shows right mesial temporal sclerosis. Video electroencephalographic monitoring records three complex partial seizures, all originating from the right temporal lobe, and interictal right anterior temporal sharp waves.
Which of the following is the most effective treatment?