ROCKVILLE, Md. - George Shafer's hands trembled so violently from Parkinson's disease that he couldn't button his shirt or feed himself - until a powerful device implanted deep in his brain cut off the shakes with electrical shocks.
Scientific advisers recommended unanimously Friday that the Food and Drug Administration approve the pacemaker-like brain implant to help Parkinson's patients and other tremor sufferers who get no relief from drugs.
"It is a wonderful miracle," said Mr. Shafer, 65, of Fort Myers, Fla., holding out nearly motionless hands. "I even made a model airplane."
At least 500,000 Americans have Parkinson's disease, a degenerative neurological disease where patients suffer uncontrollable shakes, rigid limbs and other worsening symptoms. About 2 million Americans have essential tremor, a little-understood hereditary disease that causes similar violent shaking but no other symptoms, said University of Kansas neurologist William Koller.
The drug L-Dopa helps some Parkinson's symptoms, although its effects wane over time. Only about 40 percent of essential tremor patients are helped with medicines.
The shaking is so debilitating - eventually destroying patients' ability to work, even feed themselves - that some undergo dangerous surgery to destroy a small part of the brain responsible for the trembling. But the surgery can cause permanent problems with speech, movement and swallowing.
Medtronic Inc. says it has a far less risky solution: "deep brain stimulation." With the Activa system, doctors drill through the skull and implant an electrode into the thalamus, a walnut-sized region deep in the brain. The left side of the thalamus controls movement in the right side of the body, and vice versa.
A wire runs just under the scalp down to the collarbone, where a pacemaker-sized "pulse generator" is implanted. It sends electrical waves - custom set for each patient - to the electrode, which blocks tremors by emitting constant, tiny electrical shocks.
In studies of 120 patients here and in Europe, about half saw their shakes disappear, Dr. Koller said. Others had different ranges of improvement; only seven Parkinson's patients were worse a year later.
"I can eat soup for the first time in 14 years," said study participant Maurice Long, 72, of Hutchinson, Kan., who has essential tremor. "I can go out in public and enjoy life."
Unlike surgery, Activa is reversible: Simply turn it off by running a magnet over the chest where the generator is implanted. Mr. Long did so Friday, and his hands immediately began shaking. Another swipe of the magnet to turn the system back on, and 10 seconds later his hands were steady again.
The effect was greatest for essential tremor, where testing showed patients could write, pour liquids without spilling and perform other tasks significantly better after the implant.
The implant doesn't help Parkinson's patients as much, the FDA said. That's because it only affects trembling, not other symptoms. So while studies showed implant patients could now sit still, they could not write or perform other tasks significantly better.
Mr. Shafer acknowledges his arms are too rigid to write well, but said: "I still have Parkinson's, but I say I've got 50 percent of it beat" by not shaking.
The surgery takes about five hours and is delicate. About 3 percent of patients suffer bleeding in the brain during the operation, which must be stopped to avoid permanent injury.
To control shaking on both sides of the body, patients would need separate implants in both sides of the thalamus. But the FDA's advisory panel recommended that Activa be approved for just one implantation now, because only 27 patients have been studied with double implants.
The FDA is not bound by its panel's advice but usually follows it.
Activa already is sold in Europe, where 2,000 patients have received implants since 1995. The implant, including surgery, costs about $25,000.