Online Extra: "Pacemakers" for the Rest of You

Slews of tiny devices that deliver electrical stimulation to a wide variety of organs should soon become available

Over the next couple of years, people with such debilitating ailments as epilepsy and post-stroke paralysis may have a new treatment: neurostimulation. When used to zap the heart with carefully calibrated microbursts of electricity, pacemakers and defibrillators have been proven to restore normal cardiac rhythms. Soon, similar devices may be implanted to restore normalcy to the brain and other organs.

It has been a long time coming. Medtronic Inc. (MDT ) hit the market with the first implantable pacemaker 45 years ago. As these devices became more adept -- thanks to advances in microcircuitry -- and more widely accepted, researchers began to investigate if they might also work by tingling the spinal cord or brain. After all, muscle isn't the only tissue that responds to electrical jolts. Nerve cells do, too.


  Stephen H. Mahle, president of Medtronic's cardiac-rhythm-management business, recalls that when he hired on in 1972, lab technicians at the company's headquarters in Minneapolis already were testing spinal-cord stimulation as a potential treatment for pain and movement disabilities such as foot drop, a disorder that makes people stumble as they walk. They also were experimenting with pacing the stomach to curb hunger and pacing the thyroid gland to increase its hormone output.

Some of their work never went very far. Medtronic researchers learned, for instance, that while a pulse generator could fire up a defective thyroid gland, patients could be treated just as effectively with Synthroid, a once-a-day pill, without the cost and risk of surgery.

But other experiments eventually panned out. In 1997, the U.S. Food & Drug Administration approved Medtronic's first noncardiac use of a pacemaker, to stimulate the thalamus -- a dual-lobed portion of the brain that controls movement -- to block tremors from Parkinson's disease. That same year, Medtronic also won permission to sell a device that tightens the bladder to prevent incontinence by stimulating the sacral nerve as it emerges from the lower spinal cord.


  About the same time, startups also began getting the FDA's nod for new implants. After a decade of studies, Cyberonics Inc. (CYBX ) was cleared in 1997 to commercialize a device that energizes the neck's vagus nerve to control epileptic seizures. And Advanced Bionics Corp. received permission to market its cochlear implant, a microprocessor that picks up sound waves from an external microphone and transforms them into electrical impulses in the inner ear to enable some deaf people to hear.

Since then, the FDA has allowed Medtronic, Advanced Bionics, and Advanced Neuromodulation Systems Inc. (ANSI ) each to market implantable spinal-cord stimulators for pain relief.

Now after that initial burst of approvals, a raft of new treatments may be around the corner. As early as next May, Cyberonics plans to begin marketing its vagus-nerve stimulator to treat depression. It will be the first electrical implant ever cleared to treat mental illness. The Houston-based company also plans to enroll patients in pilot studies on Alzheimer's disease, headaches, anxiety disorders, and bulimia, with the aim of getting final approval by the end of the decade at the latest.


  Medtronic also may be closing in on a number of new therapies. Its products are in clinical tests to pulse the thalamus to treat epilepsy; the occipital nerve to treat migraines, the brain's internal capsule to treat depression and obsessive-compulsive disorder, the hypoglossal nerve in the neck to treat sleep apnea, the sacral nerve to treat bowel disorders, and the stomach to treat obesity.

Explaining the device's versatility, Mark Rise, a senior scientist in Medtronic's neurological unit, likens it to a screwdriver. "You can fix a lot of different things with a screwdriver," he says. "In the same way, we can make a neurostimulator do a lot of different things." Medtronic executives say they could be on the market with a deep-brain treatment for epilepsy in two or three years.

Brand-new outfits are in the race, too. NeuroPace Inc. of Mountain View, Calif., is testing a device to control epileptic seizures by pulsing hot spots in the brain. Depending on the outcome of its experiments, the implant could be on the market in 2007. Transneuronix Inc. is in a final-phase study of its own gastric pacemaker for obesity, and executives at the Mt. Arlington (N.J.) company hope doctors will be implanting its products by 2008.


  Seattle-based Northstar Neuroscience Inc. is looking at a 2007 launch date for a neurostimulator that appears to help stroke victims regain movement in their arms and legs. In a 2004 test, for instance, 12 patients at Northwestern Memorial Hospital had the device implanted in their chests, with wires threaded to their brains near the cells that had been deadened by strokes. They then underwent strenuous physical therapy for six weeks while the pacemaker bathed the brain with low doses of electricity.

To judge the treatment's effectiveness, doctors put through the same regimen a control group of 12 stroke victims who didn't get an implant. Many of them also had greater mobility of their arms and hands after the therapy. Over the following six months, however, all but one lost most of what they had recovered, while half of the 12 patients who had undergone stimulation held onto their regained abilities, says Dr. Robert Levy, the Northwestern Memorial neurosurgeon who oversaw the study. Northstar executives think the treatment also may help people paralyzed by head injuries or cerebral palsy.

Technology should spur additional applications for neurostimulation. Advanced Bionics, now a subsidiary of Boston Scientific Corp. (BSX ), and Advanced Neuromodulation both just introduced spinal-cord stimulators with rechargeable batteries. The batteries no longer have to last for years on a single charge, so devices can be much smaller.

Because patients don't have to worry about shortening the implant's life by draining the batteries too quickly, they can also have the stimulators cranked up to overcome more-intense pain. As the batteries run low, patients simply strap on a power pack that recharges the batteries via radio waves beamed through their skin. Medtronic plans to roll out a rechargeable pain-relief neurostimulator of its own this spring.


  Even broader uses are in the works, as researchers marry these devices with miniature drug pumps to administer medicines directly to sites where they'd do the most good. The technology may not be that far away. Medtronic already sells a defibrillator that can sense fluid buildup in a patient's lungs and alert the doctor or clinic by sending radio signals to a monitoring station. And it has a line of implantable drug pumps.

Researchers at Guidant Corp. (GDT ), which also makes cardiac devices, are excited by the prospects, too. "The convergence of technologies may offer the greatest opportunities," says Dr. Joseph Smith, chief medical officer of Guidant's cardiac-rhythm-management business. "If you could combine the proven benefits of device therapy with the emerging potential of biologics, you may be able to completely rework the way we think about disease therapy."

Today, millions of people get outfitted with pacemakers and defibrillators every year for heart disease. It may not be long before that many people get electrical implants to fix what's gone wrong with the rest of our bodies, too.

By Michael Arndt in Chicago

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