Electrodes implanted deep in the brain where they provide a minute electrical charge can sharply reduce the incidence of seizures in epileptics who cannot bring their seizures under control with drugs, Stanford researchers reported Wednesday. The approach, called deep brain stimulation, is already being used in more than 70,000 Americans with Parkinson's disease and other disorders, and its use is being studied for a variety of other applications.
Epilepsy, which strikes one in 100 people, is characterized by recurrent disabling seizures or electrical storms in the brain that occur when electrical circuits there start firing spontaneously, rhythmically and uncontrollably. This can cause disturbances in vision, hearing and behavior, as well as a loss of consciousness and involuntary muscle movements that can produce injury. About two-thirds of patients can control symptoms with drugs, but that still "leaves a large number of people in great need of something better," said Dr. Robert Fisher of the Stanford University School of Medicine, who led the study.
The researchers used a battery-operated, pacemaker-like device that delivers precisely measured and timed electrical impulses to the brain. It is manufactured by Medtronic Inc. of Minneapolis, which sponsored the trial. The small battery and electronic circuitry are implanted under the skin of the chest and fine wires are threaded under the skin up to the neck, behind the ear and into the brain. For the study, the electrodes were implanted in the anterior nucleus of the thalamus, where epileptic seizures often are triggered.
Fisher and his colleagues enrolled 110 patients whose seizures could not be controlled with drugs and who were suffering an average of nearly 20 seizures per month. They implanted the device in all. During the first three months, half of the devices were turned on and half--the control group--were not, but neither patients nor doctors knew which was which. Then all devices were turned on.
At the end of three months, the team reported in the journal Epilepsia, patients whose stimulators were turned on had 40% fewer seizures than before the implantation, while those in the control group had 14.5% fewer--indicating a placebo effect. Only 7% of the patients receiving treatment experienced seizure-related injuries during the three months, compared with 26% in the control group.
By the end of the first year--nine months after the devices had been turned on in the control group--all patients reported an average of 41% fewer seizures. At two years, they reported 56% fewer seizures. Those patients who have now been followed for three years, Fisher added, have a 68% reduction in seizures. Fourteen patients reported having no seizures for periods as long as six months.
The primary side effects were limited to infections at the implant site, misplaced electrical leads that had to be repositioned, and tingling sensations.
A Food and Drug Administration advisory panel on Friday recommended that the agency approve the device for treating epilepsy. Although the agency does not have to follow recommendations from its advisory panels, it generally does.
-- Thomas H. Maugh II