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A Pacemaker for the Brain
Device offers relief from Parkinson's
Carl T. Hall, Chronicle Science Writer
Wednesday, March 21, 2001

A little-heralded device that has achieved remarkable results
controlling symptoms of Parkinson's disease is gaining new
attention even as hopes for a cure seem to dim.

The device is a "deep brain stimulator" that makes use of
electrical pulses, acting as a sort of pacemaker for the brain.

Although it may be too early to assess its full potential, the
device appears capable of restoring a measure of normal
movement in many cases.

Attempts to cure Parkinson's have focused on experimental
brain-cell transplants, a controversial procedure that might be
used someday to replace the dopamine-producing nerve cells
that die off in Parkinson's, leading to the disease's characteristic
tremor and stiff movements.

But the procedure is nowhere close to being ready for real patients.
And although there has been some encouraging scientific progress
lately, the latest clinical results, reported earlier this month,
were a terrible disappointment.

"A lot of patients are hanging on to the Holy Grail of getting a
transplant to cure them, while they're ignoring some incredibly
effective therapy that's here already," said Dr. Gary Heit,
a neurosurgeon at Stanford University.

Heit is part of a small group of neurosurgeons at Stanford and
at the San Francisco Veterans Administration hospital who have
been trying to perfect the deep-brain stimulation approach to
Parkinson's, one of the most common age- related brain disorders.

The device was first tried in Europe more than 20 years ago.
The U.S. Food and Drug Administration already has approved the
device, made by Minneapolis-based Medtronic Inc., for use for
some brain conditions.

Now the agency is reviewing Medtronic's application to begin
actively marketing the hardware for use in typical Parkinson's cases.

Even before the FDA acts, doctors are free to implant the
pacemakers in any patients the clinicians believe would benefit.

The hardware includes a battery-powered pulse generator, the
size of a large deck of cards, placed just beneath the skin of the
chest. The device is connected to wires that a surgeon threads
up the neck and into the skull, burrowing deep into the brain
through small holes drilled into the top of the skull.

Many consider it a stopgap therapy until the transplants are
proved to work.

Early clinical trials on transplants recently proved disappointing:
Most transplant recipients got little or no benefit, while some
experienced side effects worse than the disease.

Besides the medical unknowns of transplanting brain cells, the
research is slowed by ethical arguments involving the use of
transplant cells derived from human fetuses and embryos.

In contrast, neurologists say a combination of drugs and brain
pacemakers can offer relief to patients now.

"The fact is it helps, and often dramatically," said Dr. William J.
Marks, a neurologist and the medical director at the San Francisco
VA's Center for Parkinson's Disease & Movement Disorders.

In some cases, patients can achieve an 85 percent improvement on
standard symptom measures, allowing them to cut their use of
medications by half or more.

Emilio Mercado, a San Francisco-based freelance photographer
whose Parkinson's was diagnosed in 1981, has been fighting ever
since to keep the debilitating brain disease from wrecking his life.

Mercado, 67, found that he could barely make it out of his apartment
at one point, feeling like he was frozen in place. The standard
Parkinson's drugs worked for a while, but the benefits started
wearing off, requiring higher and higher doses, triggering side effects.

"You wonder what the hell's going on, and how you're going to make a
living," he said. Just over a year ago, Mercado had a pair of deep brain
stimulators implanted in two procedures at the VA. He still walks with
a pronounced stiffness and has trouble walking down inclines. But he
has been able to resume his daily tai chi workouts in Golden Gate Park,
regularly goes out on photo shoots and is a daily fixture at the Beanery,
a coffee shop near his Ninth Avenue apartment, although he often
needs a little help to avoid spills.

The electrical gizmos "are not the final answer, but they're better
than
anything else out there," he said.

Parkinson's experts have not given up on the cell transplants,
however, despite the disappointing clinical-study results.

"Of course, we would have liked a home run in the first major cell
therapy trial," said Joan Samuelson, president of the Parkinson's
Action Network, a patient-advocacy group based in Santa Rosa.

"But that's not the way science typically works."

Samuelson said it's unclear how beneficial the pacemaker
approach will be for the typical Parkinson's patient, since doctors
are still working out how best to use the devices.

"I think it's a bit early to know what the full potential of this is,"
Samuelson said. "But I don't understand it to be reparative. . . .
Reviving and restoring the cell system itself is the most obvious
strategy for a cure, and that's not what's happening here."

Nor is it clear exactly how electrical stimulation helps. One idea
is that the regular jolts of current help revive some cells that
otherwise would not be functioning properly. Certain biochemical
changes also may be taking place, affecting how well cells make use
of dopamine. The devices may also help to arrest cell death, although
that has not been proved in human patients.

The mystery doesn't bother clinicians who have little choice but to
reach for the best treatment practical for patients like Mercado,
who has no other options.

"If it works, it works," Heit said.

That may not be true in all patients, and like any brain surgery,
there are small but serious risks of infection and bleeding from
the implant procedure itself. The surgeon also has very little room
for error -- about a millimeter or so -- in placing the electrodes.

Using Electricity to Subdue Symptoms
Researchers suffered a setback recently in the search for a cure to
Parkinson's disease, but surgeons are finding it's often possible to
control symptoms using implantable neurostimulators, electrical
devices similar to cardiac pacemakers.

Electrical stimulation is delivered precisely to two small areas
on either side of the brain, known as the subthalamic nucleus
and internal globus pallidus.

Parkinson's Facts:
-- Total cases in U.S.: 1 million.
-- New diagnoses: 60,000 per year, rising as population ages.
-- Symptoms: Worsening tremor and loss of control over movement.
-- Current treatments: Drugs can be used to replenish the brain's
supply of dopamine and improve its uptake, but the benefits tend
to wear off with long-term use.

Sources:
Medtronic; The Brain Atlas; Neurosurgery Clinics of North America

http://www.sfgate.com/cgi-bin/article.cgi?file=/chronicle/archive/2001/03/21/MN195784.DTL&type=science

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