Medical Health Encyclopedia

Stereotactic Thalamotomy. Thalamotomy uses the same techniques as in pallidotomy, but it is performed on the thalamus, which is a major brain center for relaying messages. Thalamotomy has been reported to significantly reduce or completely stop tremor in 80% to 90% of patients. It does not appear to have much effect on other symptoms. Because tremor is not as significant a disability as other Parkinson's symptoms, the value of this procedure is limited. Complications are similar to pallidotomy, except there is no danger of vision loss.

Tissue Implantation

Fetal Cell Implantation. Experimental surgery has shown promise using fetal brain cells rich in dopamine implanted in the substantia nigra. The procedure is useful only in younger adults. Of great concern were studies reporting severe dyskinesia (uncontrolled movements) in implant patients. In some cases it was severe enough to make walking impossible or require pallidotomy. This has been a major setback for this approach, although techniques that put implants only in areas where dopamine is most depleted may reduce the risk for dyskinesia. (Dyskinesia is due to excessive dopamine.)

Alternative Implant Sources. The use of fetal tissue is extremely controversial, and research is ongoing for alternatives, including the use of cells from other mammals, cells from human placentas or umbilical cords, and synthetic microspheres that deliver dopamine directly to the brain. Some researchers hope to use cloning techniques on animal fetuses as a source for dopamine-producing nerve cells. Animal and laboratory studies are also using gene therapies and other advanced treatments for transplanting dopamine-producing cells or nerve-protecting cells into the brain.

Radiosurgery and the Gamma Knife

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Radiosurgery is a technique typically used for brain cancer. It employs a so-called gamma knife, which is not a knife at all, but 300 intersecting radiation beams that are directed through holes in a helmet to target precisely affected sites in the brain. The gamma knife is now being investigated as tool for both thalamotomy and pallidotomy in patients who are not candidates for standard surgery. Early studies are showing that it improves symptoms after about six to eight weeks, but it can have significant and very serious side effects. In one study, one patient out of eight patients died of complications. There were also a number of distressing side effects, including weakness and partial paralysis. In addition, the operated areas were significantly off target.

Transcranial Magnetic Stimulation

Transcranial magnetic stimulation (TMS) employs high frequency magnetic pulses that target affected areas of the brain. It is noninvasive and is being investigated for Parkinson's disease, and one 1999 study reported symptom improvement in patients treated twice a day. Unfortunately, a 2001 study reported that symptoms actually worsened with this approach.