CHICAGO—Among patients with medically intractable partial seizures who received treatment with a responsive cortical neurostimulator, the rate of sudden unexplained death in epilepsy (SUDEP) was lower than that estimated for patients with medically intractable epilepsy overall and for patients being considered for epilepsy surgery, according to research presented at the 140th Annual Meeting of the American Neurological Association. In addition, electrocorticographic data recorded by the neurostimulators indicate that SUDEP sometimes occurs after epileptiform discharges, such as spikes or electrographic seizures.
To estimate the rate of SUDEP in patients with medically intractable partial onset seizures who are treated with the RNS System (NeuroPace, Mountain View, California), Martha J. Morrell, MD, Chief Medical Officer of NeuroPace and Clinical Professor of Neurology at Stanford University, and colleagues calculated the rates of probable and definite SUDEP according to total implant and total stimulation years.
NeuroPace receives information about all deaths that occur in patients treated with the RNS System, and a SUDEP adjudication committee assessed all patient deaths using established criteria to determine whether or not a death was probably, possibly, or definitely related to SUDEP. The committee comprised an epileptologist/epidemiologist, a second epileptologist, and a pathologist/medical examiner who reviewed all available medical records related to the terminal event.
A total of 514 patients had the RNS System implanted—256 within clinical trials and 258 after FDA approval—as of September 1, 2015. The patients received responsive stimulation for a total of 1,735.5 patient-years. Patients had the RNS System implanted for a total of 1,873 patient-years. Fourteen patients died. Five deaths were considered probably or definitely related to SUDEP—one probable and four definite. Two other deaths were deemed possibly related to SUDEP.
The rate of probable and definite SUDEP was 2.7 per 1,000 years of implantation, and 2.3 per 1,000 years of responsive stimulation.
“Patients in the RNS System trials were at high risk for SUDEP, given medical intractability, long duration of epilepsy, high seizure burden, and [antiepileptic drug] polytherapy,” the investigators said. “However, the SUDEP rate was 2.5/1,000 [in the clinical trial] and 2.3/1,000 for all patients treated, which is lower than the estimated rate with medically intractable epilepsy and for patients being considered for epilepsy surgery.” SUDEP rates are estimated to be 3.2–5.9/1,000 patient-years in patients with medically refractory epilepsy, and 6.3–9.3/1,000 patient years in candidates for epilepsy surgery, the researchers said.
Data about epileptiform activity and electrographic seizures that are provided by the RNS System may contribute to a better understanding of the events and mechanisms underlying SUDEP, Dr. Morrell and colleagues said.
—Jake Remaly
