Deep-Brain Implant OKd for Uncontrolled Shakes
The Food and Drug Administration on Monday approved a bold deep-brain implant that promises to ease the uncontrollable tremors experienced by thousands of patients with Parkinson’s disease and an equally disabling disorder called “essential tremor.”
The deep-brain stimulator, which has been available in Europe for several years, has enabled many patients to once again eat, drink, write and perform an array of daily living activities by themselves, said Dr. Michael J. Friedman, acting FDA commissioner.
The device, an electrode that emits a steady stream of electrical pulses, has proved particularly effective for patients with severe essential tremor.
It has also significantly reduced tremors among Parkinson’s patients, but because it does not treat the other symptoms of the disease, it produced less dramatic effects on their quality of life, according to the FDA and a spokesman for Medtronics Corp., the device’s Minneapolis-based manufacturer.
Approval of the deep-brain stimulator follows by one month the FDA’s go-ahead for a new Parkinson’s medication called Mirapex. The approvals mark the end of a period of little activity on medications and procedures to treat Parkinson’s, according to an FDA spokesman.
The stimulator, like the new drug, treats the symptoms of Parkinson’s but not the cause, which is the death of the brain cells that produce a chemical called dopamine. Dopamine is one of the brain’s neurotransmitters, which carry the nervous impulses that enable thought and control the body.
The closest thing to a cure for Parkinson’s generally available now is a transplant of fetal brain cells to replace the cells that have died in the diseased brain.
A scientifically controlled trial of the fetal-tissue transplant, supervised by the National Institutes of Health, is being conducted at the University of Colorado. In addition, three other hospitals, including Good Samaritan Hospital in Los Angeles, are performing the $40,000 operation privately.
The basic Parkinson’s treatment remains a medication called L-dopa, which is taken orally and is converted to dopamine inside the brain. L-dopa’s effectiveness, however, wears off with time, and its side effects, which include violent, uncontrollable movements, worsen.
The cause of Parkinson’s disease remains unknown, although researchers recently announced they had located a faulty gene that seemed to be responsible in a family that has experienced an unusually high incidence of Parkinson’s over several generations.
The deep-brain stimulator, the latest device to combat the disease, won FDA approval for use only on one side of a patient’s brain--to help control the tremor on the other side of the body. Parkinson’s typically affects one side of the body more than the other.
*
Studies are still underway to evaluate the safety of implanted electrodes on both sides of the brain and no results will be available for several months, the FDA said.
About 2 million Americans experience essential tremor, a little-understood neurological disorder that usually runs in families. It can cause severe shaking, but few other symptoms.
Parkinson’s affects an estimated 500,000 to 1 million Americans, causing tremors, rigidity, slowness or difficulty in moving about and, in some, mental deterioration.
To implant the $25,000 “Activa Tremor Control System,” surgeons drill through the skull and then 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. Doctors recommend the implant for the hand patients use most.
It is then connected by wire under the skin to a pacemaker implanted in the chest. Upon activation, the pacemaker sends a steady stream of tiny electrical pulses to the brain, blocking the tremor. It can be controlled by the patient, who can turn it on or off simply by placing a hand-held magnet over it.
Part of Activa’s appeal is that the shocks can be quickly adjusted by radio waves if patients need more or less stimulation, said Dr. Jean Pintar Hubble of Ohio State University Medical Center, who helped test the implant.
Patients may want to consider the procedure if drugs or other surgeries fail to decrease violent trembling, an FDA official said. Some patients undergo dangerous surgery to destroy a small part of their brain that causes the trembling. But that surgery can cause permanent problems with speech, movement and swallowing.
Monday’s FDA announcement contained several cautions.
* “A few” stimulator recipients experienced a worsening of their overall conditions, with increased tremors and difficulties in movement.
* About one-third of the patients experienced a tingling sensation in the head and hands. (This was controlled by physicians who changed the stimulation settings on the device.)
* The generator must be replaced every three to five years.
* “In a number of patients,” wires broke during the course of the study and had to be replaced.
The FDA’s approval of the stimulator was based on a review of clinical studies on safety and efficacy conducted at about 20 medical centers in the United States and Europe.
In the U.S. studies, the device was implanted in 113 people with Parkinson’s; 67% of the patients showed decreased tremors as a result. Of the 83 people with essential tremor, 58% showed improvements. The FDA said the European results were similar.
The agency is requiring Medtronics Corp. to conduct additional studies to ascertain the device’s long-term safety and efficacy, including the effects on patients when the wires from the electrodes to the pacemakers break and must be replaced.
Medtronics also is to study the long-term effects of electrical stimulation on brain tissues.
(BEGIN TEXT OF INFOBOX / INFOGRAPHIC)
How Brain Pacemaker Works
A pacemaker-type brain implant helps Parkinson’s patients and other tremor sufferers. The operation to install the device takes five hours and costs $25,000. Shakes disappear for half the users.
1) A hole is drilled through the skull and an electrode is implanted into the thalamus, a walnut-sized region that controls movement.
2) A wire runs under the scalp down to the collarbone, where a pulse generator is implanted.
3) The generators sends constant, tiny electrical shocks to the thalamus. Brain signals that cause tremors are blocked.
4) The patient can program the generator by an external unit and turn it on and off by running a magnet over the chest.
Source: Medtronic Inc.
