Only half of the people with epilepsy currently can achieve control with treatments. Almost a third of people with epilepsy have a refractory form of the disease that does not respond well to existing anti-epileptic drugs. Those patients are also not helped by the one currently FDA approved implanted device —Cyberonics’ Vagus Nerve Stimulator (VNS). There is hope, however, for those sufferers.
A new type of implantable seizure control, called “closed-loop” has been designed to monitor the seizure focus, perceivearrangements of electrical activity that designate a seizure is beginning, and quickly react without outsideinvolvement. Those responses could consist of electrical stimulation, cooling or concentrated drug delivery—all meant to interferewith the seizure activity and stop the seizure. The idea behind this device comes from the world of cardiac implants, such as the implanted defibrillators that monitor the heart and provide stimulation in reaction to an event.
There is only one closed-loop device currently being tested- NeuroPace’s Responsive Neurostimulation System (RNS). It is an electrical-stimulation implant with two leads with four electrodes that are placed in the brain at the focus of the seizures. The RNS delivers direct electrical stimulation to disturb the activity and regulate the area that it found electrical activity that indicates the start of a seizure. RNS is surgically implanted in a section of the patient’s skull and can be accessed through outpatient surgery when the battery needs to be changed. It is undetectable to the patient and others, which are all great design benefits for patients and doctors.RNS can also function to record information on electrical activity in the brain throughout the day for later review. The implant comes with an interface for remote patient observing.RNSiscurrently seeking FDA approval.
The results of RNS’ trials have been mixed. Seizure frequency was lowered by about fifty percent in approximately half of the tested patients.
“For a patient to go through permanent implanting of the device on the skull, and electrodes over the brain, which is what is needed for RNS, you’d want it to eliminate most or all seizures, which isn’t the result in most patients,” says John Miller, director of the University of Washington School of Medicine’s Regional Epilepsy Center at Harborview in Seattle.
There are ways to improve the device, Miller says, including treating only patients that do not respond to other treatments, finding better places to attach the electrodes, and accelerating RNS’ detection of seizures.
RNS is promising, but is still a ways off from being refined and effective enough to get FDA approval.
About the Author: This guest post is contributed by Debra Johnson, blogger and editor of live out nanny.
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