DA approval for the device was supported by the Stimulation of the Anterior Nucleus of the Thalamus in Epilepsy (SANTE) trial, which found patients implanted with it had a 75% reduction in seizures after seven years. 

The randomized double-blind study was conducted at 17 centers in patients ages 18-65 with an average of six or more seizures per month. 157 patients enrolled in the study, but only 110 subjects were implanted with the device after patients discontinued the study between enrollment and the operation phases. 

Robert Gross, a professor at Emory University and the neurosurgical primary investigator for the trial, said the device offers "an important surgical treatment option for patients who suffer from epilepsy and do not respond to medication." 

FDA says the device should only be used for those over the age of 18 who are diagnosed with epilepsy with partial-onset seizures resistant to three or more antiepileptic medicines. The regulator is requiring annual reports from Medtronic with the number of DBS devices sold and distributed to help monitor how often adverse events occur.

Medtronic is in the process of starting a 140 subject post-approval study to examine the safety and effectiveness of the device, according to Mike Daly, vice president of the company's brain modulation business. The post-approval study appears to be a prospective single-arm study, according to FDA's PMA approval letter.

"The primary safety objective will be to demonstrate that there is not a 20% worsening in seizures over time in subjects treated with the DBS system beginning at 6 to 12 months post-implant and extending long term (three years)," the PMA approval letter states. "A secondary safety objective will be evaluation of the Sudden Unanticipated Death from Epilepsy (SUDEP) rate at 3 years."

Neuromodulation competitors Abbott and Boston Scientific have also enhanced their DBS offerings in recent months, both addressing Parkinson's disease.