CHAPEL HILL -- Elizabeth Moore, 68, used to shave her head every year. A Zen priest who lives at the Zen Center in Chapel Hill, Moore did the ritual as a form of self sacrifice -- a Buddhist way of renouncing material pursuits.

That was until November 2007 when Moore decided that she could never again put a razor to her head without thinking twice.

Beneath Moore's scalp, embedded deep in her brain, lies a pair of electrodes. Wires from the electrodes snake their way under her skin down to her shoulders and connect the electrodes to a pair of pacemakers implanted above her breasts. The pacemakers generate tiny jolts of current that the electrodes deliver to the brain.

The current keeps Moore in control of her body. Without the electrodes and pacemakers, Moore's body would twist and turn uncontrollably from time to time.

Moore has Parkinson's disease and the surgery that changed her life for the better is called deep brain stimulation. About 1.5 million Americans suffer from Parkinson's disease, a neurological disorder that leads to tremors, loss of balance and rigidity. In the past, doctors relied mostly on drug treatment. Now neurosurgeons at UNC use deep brain stimulation for some patients.

Deep brain stimulation, unlike electroconvulsive therapy, or shock treatment, uses a much smaller current targeted to a specific brain region called the thalamus and is a one-time procedure. Patients who don't respond to or tolerate medication may be candidates for deep brain stimulation -- a treatment of last resort that could dramatically improve a patient's condition.

"Deep brain stimulation is all about quality of life," said Dr. Eldad Hadar, Moore's neurosurgeon at UNC Hospitals. "In some patients, the medication starts to lose effectiveness. It can be instantaneous. They'll be walking through a shopping mall and then they just freeze. It's embarrassing. It's functionally limiting."

Alexander Troester, a neuropsychologist at UNC Hospitals, says deep brain stimulation isn't a treatment for everybody.

Parkinson's patients who don't tolerate medication or who develop severe medication-related side effects such as hallucinations may be good candidates for deep brain stimulation, Troester says. Extensive neuropsychological testing determines who may be a good candidate.

Although deep brain stimulation works, doctors don't understand exactly why or how.

"There's something about DBS that stops the disease from progressing beyond the point when we implant the electrodes. We don't entirely understand that," Hadar says.

A study published in January's Nature Medicine revealed that a brain chemical that causes drowsiness may be responsible for the therapeutic effect of deep brain stimulation.

People with Parkinson's disease and tremor have rigid muscles and a rhythmic trembling of the limbs, head and vocal cords. Some lose physical movement altogether. Scientists believe that hyperactivity in specific brain regions causes the symptoms. Deep brain stimulation reduces the hyperactive electrical stimuli and helps patients regain some control over their muscles.

Researchers at the University of Rochester Medical Center in New York, headed by Dr. Maiken Nedergaard, found that a brain chemical called adenosine is released by a group of brain cells dubbed astrocytes, which lie next to the nerve cells in the thalamus -- the area where the electrical impulses are delivered during deep brain stimulation. Astrocytes are brain cells that feed nerve cells and repair damaged nerve cells.

The team showed that an infusion of adenosine in the brains of mice reduced abnormal signaling without any deep brain stimulation. Further, when the team blocked the entry of adenosine into the nerve cells of mice using genetic techniques, deep brain stimulation did not work.

Adenosine, a brain chemical that causes drowsiness, builds up in the brain during the day and induces sleep at night by controlling brain signaling.

Deep brain stimulation may cause side-effects such as cognitive dysfunction, memory loss, depression and hallucination in some patients. Others have reported losses of insight, verbal fluency and abstract thinking.

The surgery involved in inserting the electrodes into the brain may damage the brain irreversibly.

"In order to put one of these things in, we have to drill a hole in the head and insert electrodes into the brain. There's the risk of infection, creating a hemorrhage and giving the patient a stroke," Hadar says.

About 8 percent of patients receiving deep brain stimulation get an infection while 2 percent suffer a stroke, Hadar says.

The most devastating consequence of hitting a blood vessel during brain surgery is a stroke, in the best case scenario, says Dr. Xuemei Huang, a neurologist at UNC. "In the worst case scenario, it's death," she adds.

"Some people reject the electrode or the effect may wear off after several years," Nedergaard says.

Moore says she is satisfied with the surgery thus far, although Hadar cautions that it's too early to tell. Hadar operated on Moore in November 2007.

Moore adds that she wished the pacemakers weren't so bulky and that on some mornings in the shower, she can feel the wires squiggling beneath her skin.

If confirmed, Nedergaard's findings may represent the first step toward obviating the need for surgery in deep brain stimulation. The challenge is to find a way to deliver adenosine specifically to the thalamus.

"If you increase adenosine in the whole brain, the patient goes to sleep," Nedergaard says.

Genetic approaches that target specific nerve cells may help deliver adenosine where it is needed, but gene targeting in the human brain remains a distant dream.

Troester says that the role of adenosine in deep brain stimulation had been suspected for very long, but no one knew what exactly adenosine does to brain signaling. Nedergaard's results need to be confirmed, he warns.

"The jury's out, and we're going to have to wait for some time before that becomes a convincing story," he adds.

Most patients who undergo deep brain stimulation take much lower doses of medication than those who don't, Troester says.

Troester's analysis of several studies concluded that while loss of verbal fluency is a common side-effect of deep brain stimulation, changes in cognitive abilities such as attention and memory are rare and fleeting. His results were published in The Lancet in July 2006.

Deep brain stimulation and the associated surgery could cost between $50,000 and $80,000, Troester says. Some insurers cover the cost.

Although the FDA has approved the use of deep brain stimulation only to treat Parkinson's disease, essential tremor and some cases of dystonia, some doctors use it as experimental therapy or a last-ditch effort for patients suffering from chronic pain, depression and obsessive-compulsive disorder.

Moore no longer has the tremors thanks to deep brain stimulation.

"I'm taking no medication whatsoever, except a tiny bit of Amantadine. No Sinemet. No Requip. My tremors are under fairly decent control most of the time," she says.

Sheila Read contributed to this story