Aug. 27, 1998 LOS ANGELES (August 23, 1998) - A new type of brain surgery at Cedars-Sinai Medical Center's Neurofunctional Surgery Center, done while the patient is awake, is helping to control tremors in Parkinson's Disease patients like Dennis Turner, 56, a former engineer at Southern California Edison's San Onofre Nuclear Generating System. Stereotactic-Guided Placement of a Deep Brain Stimulator has been available in Europe for several years, but only received FDA approval last year for use in the United States.In addition to implanting a deep brain stimulator during the Aug. 11 surgery, physicians harvested some of Turner's brain cells, which will be genetically engineered and implanted at a future date. Researchers hope that the genetically engineered cells will replace defective cells, thereby offering the possibility of a cure for this disease which presently has none.
According to Michel F. Levesque, M.D., Director of Cedars-Sinai's Neurofunctional Surgery Center, the state-of-the-art procedure utilizes magnetic resonance imaging (MRI) and a stereotactic frame to identify the exact location in the mid-brain that is causing tremors. The frame is placed on the patient's head like a crown. Coordinates are calculated digitally through a computer, showing the neurosurgeon precisely where to insert a battery-powered electrode (stimulator) that will send impulses to the thalamus -- the part of the brain that activates the tremors associated with Parkinson's Disease.
Once the target area has been identified, a 14mm hole -- about the size of a 50-cent coin -- is drilled in the crown of the patient's head, and an external voltage stimulator (test electrode) is carefully threaded between the two hemispheres of the brain to the thalamus. This electrode enables neurosurgeons to do extensive stimulation testing during surgery to determine precisely where within the thalamus to position the stimulator. The testing must be done while the patient is awake so that he or she can move his hands, fingers or arms when asked to do so, or respond verbally to questions asked by the surgical team. "As we move the test electrode, we watch the patient closely to identify exactly when the tremor has completely stopped. Then we know to exactly where to place the stimulator," says Dr. Levesque. Although awake, the patient does not experience pain during this testing, only tingling sensations.
To "double-check" the location, Dr. Levesque also does a Micro Recording or Internal Brain EEG. Working with two neurophysiologists who designed the Micro Recording Electrodes, he takes this extra measure to be absolutely certain that he has located the nucleus of the thalamus. Once the team is satisfied that the location is exact, the patient is given a general anesthesia, and surgeons tunnel down from the top of the head to just below the clavicle in order to insert a tiny generator - the size of a business card - in the patient's chest. This generator is battery-powered and is turned on and off by the patient with a magnetic device. "Many patients do not experience tremors during sleep, so they like to turn off the generator when they go to bed and conserve the battery," says Dr. Levesque. Batteries usually have to be replaced after 10 years, but can last longer if they are not operated continuously.
The entire procedure usually takes about three to four hours. After surgery, the patient typically spends one night in the Cedars-Sinai Intensive Care Unit for observation, has a CT scan the next morning, and then goes home in a day or two. A check-up five days after surgery is followed by a two-week check-up, at which time the generator is turned on using the magnet. While many physicians turn on the generator at the time of surgery, Dr. Levesque prefers to wait about two weeks to give the patient time to recover from the surgery and for any swelling to diminish.
At this two-week check-up, Dr. Levesque also programs the generator using a special computer in his office. "The computer programs the stimulation levels," says Dr. Levesque. "Different people require varying levels of stimulation. Also, because Parkinson's Disease is a progressive disorder, additional programming will likely be needed to adjust the stimulation levels."
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