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When scientists began using deep brain
stimulation (DBS) in patients with Parkinson's disease, they noticed
these patients were no longer forced into twisted, contorted positions
-- a common side effect of Parkinson's known as dystonia.
Some 50,000 children in North America
are born each year with a severe, genetic form of dystonia, which
shows up in the first or second decade of life. These young patients
can become torqued in unnatural postures and have to be fitted with
rods in their spines to keep them semi-erect. Those with advanced
disease may become wheelchair-bound or bedridden.
After noticing that dystonia symptoms
subsided with use of DBS in Parkinson's patients, doctors began
to consider applying the technique in patients with the genetic
form of the disease, says Helen Bronte-Stewart, MD, director of
the Stanford Comprehensive Movement Disorders Center. They reasoned
that these patients would benefit from the same treatment: electrical
stimulation of the part of the brain known as the globus pallidum.
"They found that the dystonia of Parkinson's
was cured with this target and they thought they should try it in
people with genetic dystonia -- and it has worked. The results are
quite remarkable," says Bronte-Stewart, who is an assistant professor
of neurology.
In the past two years, Bronte-Stewart
has treated two dystonia patients and is working with three or four
others who are potential candidates for the procedure, she says.
A videotape of her first two patients shows a young man and a young
woman literally transformed from hunched, twisted figures to individuals
with no apparent disability.
One patient, a man in his 20s, was
unable to walk before the surgery, his head bent low and his arms
curled about his torso. After DBS on one side of the brain, the
slender, red-haired patient walked with a cane down the clinic halls
and his body had only a slight twist to it. After a second surgery,
on the other side, he strode into the clinic and then broke into
a run, smiling at his caregivers.
The same results are apparent in a
second patient, a 23-year-old woman, who was wary of DBS and chose
instead to have a pallidotomy, a treatment in which doctors destroy
cells in the globus pallidum that cause dystonia. Bronte-Stewart
says cell destruction and stimulation both can achieve similar effects.
A pallidotomy performed on both sides of the brain, however, can
be somewhat risky, as the accidental destruction of nearby cells
can leave patients with speech and swallowing problems, she says.
In the young woman's case, the surgery
went remarkably well. When she arrived at the clinic for her first
visit, she was completely bent over and unable to hold her head
up without propping it up with her hands. Her body was twisted in
an awkward posture. After a pallidotomy, performed in April on the
right side of her brain, the trembling in her left hand disappeared
and she had better use of her left arm and leg, although her right
side remained slightly twisted. Her right side still dragged her
down.
Four days after the surgery on her
left side, she strolled upright into the clinic with no signs of
any difficulty. She now attends college and is doing well, Bronte-Stewart
says.
Bronte-Stewart notes that it was by
happenstance -- not by rigorous science -- that doctors chose the
globus pallidum as a DBS target for these dystonia patients.
"It isn't based on any careful analysis
of which place we should quiet down," she says.
Bronte-Stewart is now in the process
of establishing a deep brain recording unit at Stanford, in which
she and colleagues will systematically test patients with the goal
of identifying the best sites and best methods for electrical stimulation.
Identifying which areas of the brain
are abnormal also could be useful to geneticists, who have been
tracking the molecular pathways of the disease. The gene for early
onset dystonia, known as DYT1, was identified in 1997 by a team
that included Neil Risch, PhD, a professor of genetics at Stanford.
RUTHANN RICHTER
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