Study: Brain ‘Pacemaker’ Battles Parkinson’s
Implanting minute electrodes in the brain is the most effective treatment for advanced Parkinson’s disease and has fewer side effects than widely used surgeries that destroy brain tissue, an international team reports today.
The technology, a kind of brain pacemaker, “can literally restore patients to independent function” when conventional drugs can no longer help them, said Dr. C. Warren Olanow of the Mount Sinai School of Medicine in New York City, who co-chaired the study reported in today’s New England Journal of Medicine.
The implants could be used effectively in as many as 200,000 of the nation’s 1 million Parkinson’s patients, he added.
Although surgical destruction of small areas of the brain may still have a role in a small number of Parkinson’s patients, he added, that operation “basically should no longer be done.”
Parkinson’s, which strikes as many as 100,000 Americans each year, is characterized by severe tremors and rigidity in the limbs and loss of muscle control. Although its cause is unknown, the disorder results from the death of brain cells that produce a neurotransmitter called dopamine, which plays a key role in transmitting commands from the brain’s muscle-control centers.
The primary treatments for the disorder are drugs, such as levodopa, that alleviate symptoms by increasing dopamine concentrations in the brain. Over time, however, patients who use these drugs begin to suffer from dyskinesia, a severe inability to control muscle movements.
Researchers have found that abnormal brain signals in Parkinson’s are produced by two small regions of the brain, the globus pallidus and the subthalamic nucleus. One commonly used treatment has been to surgically destroy those areas on one or both sides of the brain. The treatments are called a pallidotomy or a thalamotomy, depending on which brain region is destroyed.
Both procedures control symptoms, but they can have disabling side effects. Patients can have difficulties speaking and swallowing, decreased ability to initiate movement, language problems and difficulty in reasoning.
A newer approach is to implant tiny electrodes at either brain site and bathe the tissue in high-frequency radiation. The stimulation has the same benefit as destruction of the tissue, but without the side effects. A small device similar to a pacemaker is implanted under the skin to power the electrodes. The device itself costs about $10,000, and the entire procedure as much as $30,000.
In research financed by Medtronic Inc. of Minneapolis, which manufactures the implant device, the team studied 134 patients at 18 medical centers in the United States, Europe and Australia. For 96 patients, the electrodes were embedded in the subthalamic nucleus on both sides of the brain; for 38, the globus pallidus. The devices could be turned on and off at random, with neither the patients nor their physicians knowing when they were on.
When researchers examined the results, the impact was “fantastic,” Olanow said. When the probes were turned on, “the patients were very dramatically improved in a way that medical therapy [drugs] couldn’t do.”
Most dramatically, in patients with the subthalamic implant, the proportion of time that patients had good mobility without dyskinesia increased from 27% to 74% after three months. For those with the implant in the globus pallidus, the comparable increase was from 28% to 64%.
Overall, stimulation of the subthalamic nucleus was associated with a 49% improvement in muscle control, and stimulation of the globus pallidus with a 37% improvement. The improvement was measured with a scale normally used to measure muscle control in Parkinson’s patients.
“The benefits of brain stimulation are truly remarkable,” said Olanow, “especially when you consider that none of the available medications for Parkinson’s disease make anywhere near that kind of difference for most patients in advanced stages, and that all of them invariably create intolerable side effects over time.”
Patients in the study were followed for only six months, but Olanow suggested that the positive effects “persist indefinitely, as far as we know. It can go on for years and years.”
The treatment has some risks, however. Seven patients suffered bleeding in the brain--which could be controlled--and two had to have the devices removed because of infections associated with the electrical leads.
