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Dear All, Periodically, someone has a question about "electrical brain stimulation" for PD and other movement disorders. Here is a simplified picture of the current state of the surgery: There are currently three types of "electrical brain stimulation for movement disorders". The only current commercial source of the implanted device, which is essentially a high-powered heart pacemaker, is Medtronic Inc., although another company is currently preparing to enter the market. All three implants may be placed unilaterally (one side of the brain to control symptoms on opposite side of body) or bilaterally (both sides of brain to control symptoms on both sides of body). In all cases, the electrode is a flexible cable with four metal contacts at the end, which is guided into the brain using stereotactic techniques just like for ablative (destructive) surgery like pallidotomy and thalamotomy. Either on the same day as the brain implant is performed or a few days later, the stimulator (about the size of a "Mint Patty" candy bar is surgically placed below the skin in the chest. Although the goal of the stimulators is to stimulate, as opposed to destroy tissue, there is some tissue damage as the electrode is guided to the correct location deep inside the brain. Nobody knows why it works. The most accepted hypothesis is that the stimulating electrode over-stimulates nerve cells in the target area, which makes them incapable of functioning. Thus, the results are very similar to destroying the cells, except that the stimulator can be turned off, unlike a heat lesion made in ablative surgery. Depending on the amount of use, the batteries need changing (minor surgery) every few years. The three different targets are: 1. Thalamic Implant: Stimulating electrode is placed into the thalamus. Controls tremor only. Approved in Europe and USA. 2. Pallidal Implant: Stimulating electrode is placed in the globus pallidus. Controls dyskinesias, slowness, lack of movement, tremor. Effects very similar to pallidotomy. Approved in Europe, not in USA. Clinical trials ongoing in USA. 3. STN Implant: Stimulating electrode is placed in the subthalamic nucleus (this is distinct from the thalamus). Controls dyskinesias, slowness, lack of movement, tremor. Effects similar to pallidotomy. Approved in Europe, not in the USA. Clinical trials ongoing in USA. There is currently debate as to whether the STN or the globus pallidus is the best spot to stimulate for major PD symptoms. My guess is that all forms of stimulation will be approved in Europe and USA within one year. Hope this helps, Andy