- Patient should have history of a trial of at leas four drugs, including one trial of a combination of two concomitant drugs without successful seizure control. Vagal nerve stimulation, RNS deep brain stimulation, or the ketogenic diet can be considered equivalent to a drug trial. Patient suffering from an epileptic syndrome that is known to be refractory to treatment, such as Dravet or Lernnox Gastaut Syndrome, may be included after a trial of only two drugs