Implantable Computer Device Aborts Seizures

New Hope for Patients with Focal Onset Epilepsy

Epilepsy, a neurological disease affecting an estimated 2.7 million individuals in the United States, causes unpredictable and potentially dangerous seizures. Anticonvulsant drugs serve as the foundation for epilepsy treatment regardless of the many known brain abnormalities, focal or diffuse, that produce the patient’s seizures.

Unfortunately, limited efficacy and problematic side effects make drug therapy alone an imperfect solution, says UAB epileptologist A. LeBron Paige, MD. “An estimated 60% of epilepsy patients are thought to have seizures that arise from a discrete area of the brain, or seizure focus. Resective epilepsy surgery offers these patients the potential of a definitive cure for their devastating seizures.”

“Although resection can render patients seizure free, the risk to surrounding normal tissue must be carefully evaluated,” he says. “In most cases a border zone of nonfunctional tissue surrounding the seizure focus allows its excision without risk to normally functioning brain.”

In a portion of candidates, however, presurgical testing reveals the seizure focus is dangerously close to or within an area of vital, normally functioning brain. “In these cases, the risk of damage to adjacent areas of eloquent cortex may be too great to perform the operation, ending the patients’ surgical candidacy and leaving medication as their only treatment option,” he says.

UAB’s Epilepsy Center now offers hope to this group of patients in the form of an electrical stimulator. Currently in phase 3 clinical trials at UAB and other Level IV epilepsy centers around the nation, the Responsive Neurostimulator (RNS) is an implantable computer device that continuously monitors the brain’s electrical activity for the earliest signature of seizure onset. When the device detects a seizure, it sends an abortive burst of painless electrical impulses directly to the area of affected brain.

Surgeons implant the pocket watch-sized RNS in a recess created in the outer portion of the skull just under the scalp. Two electrode leads exit the RNS, pass through a small hole in the skull, and are located as close as possible to the site of seizure origin. The leads are sutured in place where they are in permanent contact with the brain. Placing the electrodes near the seizure focus is critical since prompt detection and early stimulation offers the best chance of disrupting seizure spread, Paige says.

A special hand-held transceiver wand communicates with the device, uploading commands and downloading stored seizure data to a laptop computer. Periodic review of this valuable data by the patient’s epileptologist allows for fine-tuning of the device’s seizure detection and stimulation settings.

“Optimizing settings improves seizure control and allows patients to rely less on anticonvulsant drugs, reducing side effects and expense and improving overall quality of life,” he says. “Beyond its benefit to individuals, the device offers the unprecedented ability to record continuous electrocorticography in free-ranging ambulatory patients over a span of years. The RNS is poised to make significant contributions to our treatment as well as our understanding of human epilepsy.”

For more information:
Dr. LeBron Paige
1.800.UAB.MIST
mist@uabmc.edu