Shock to the System
How a
radical new implant that zaps patients back to life is upending our
understanding of the brain
By Gregory Mone
| January 2007
For
six years after a brutal beating, a 38-year-old man lay in a
minimally conscious state, effectively unable to communicate. Then,
with the permission of his family, a team of neuroscientists at New
York–Presbyterian/Weill Cornell Medical College and the Cleveland
Clinic Foundation attempted a last-resort experimental treatment known
as deep brain stimulation, or DBS. Using brain scans as a guide, they
implanted tiny electrodes deep in the man’s head and wired them to a
pacemaker-like device beneath his collarbone.
Once switched on, the device began
sending pulses of electricity to his thalmus, an area of the brain
thought to influence consciousness. After two years of therapy, the
scientists rocked the medical world this October with their stunning
results: The man was awake, able both to speak and to understand speech.
That was the first reported case
in which DBS had proved effective in a patient suffering from a brain
injury. And the technique has been steadily emerging as a potentially
powerful treatment for a wide range of diseases and disorders,
including depression, Tourette’s syndrome and Parkinson’s disease. More
than 35,000 Parkinson’s patients have the electrodes implanted in their
brains, and although no overall statistics have been released,
neurologists estimate that 80 to 90 percent of patients experience
massive reductions in their tremors. “Sometimes it’s startling, to the
point oftears in everybody’s eyes,” says Stephen Grill, a neurologist
at the Parkinson’s and Movement Disorders Center of Maryland.
With such remarkable clinical
success, DBS is doing more than giving patients new hope—it’s changing
how scientists understand brain disorders. Neurologist Helen Mayberg of
Emory University says she conceives of depression as a kind of
circuit-board malfunction rather than a simple chemical imbalance.
“It’s not just about being a quart low on serotonin,” she says.
Mayberg is
currently leading a
research study testing DBS’s effectiveness against treatment-resistant
depression. More than one million people suffer from this condition
and, until now, their only option was electroconvulsive therapy, the
neurological equivalent of a cardiac defibrillator. ECT has proven
effective at fighting depression—more than 100,000 people receive it
annually—but it can also lead to memory loss. DBS, in contrast,
delivers smaller zaps—usually around three volts—to better-targeted
areas of the brain, with no reported side effects related to memory or
anything else. “We’re not just rebooting the computer,” Mayberg says.
“We know precisely what we want to have happen.”
By tweaking specific parts of the
brain, scientists could in theory not only restore damaged areas but
also enhance uninjured ones, improving memory and raising IQs in
healthy people. Cornell Medical College neurologist Daniel Herrera
recently announced that, when applied to a major communication center
in the brain called the subthalamic nucleus, DBS actually improved
rats’ memory.
Yet for all the treatment’s
potential, scientists don’t know exactly why it’s so effective. “We
know that it’s working,” says Michele Tagliati, co-director of the
brain-stimulation program at the Mount Sinai School of Medicine. “We
don’t know exactly how it’s working.” And although the side
effects have so far been minimal, the scientists are quick to point out
that DBS is still brain surgery, so there can be complications, such as
lesions developing from the implanted electrodes.
Mysterious as DBS is, researchers
are optimistic about its potential, and there’s still plenty of room
for refinement. Tagliati and other scientists are exploring possible
changes to the electrodes, along with variations in the type and amount
of current that they use. Psychiatrist Sarah Lisanby, director of the
brain-stimulation division at Columbia University, says the combination
of current clinical success and possible technological advances points
to a bright future for the field: “We could very well be standing on
the threshold of a new frontier.”
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