Principal speaker was Dr. Gary Heit of Stanford University. Dr. Heit made an excellent presentation on DBS and Medtronic's Activa(tm) device, explaining its role in controlling tremor in Essential Tremor and Parkinson's.

At present, Dr. Heit explained, the FDA has approved the use of the Activa(tm) only for use with the electrode connected to the Vim (ventral intermediate nucleus) of the thalamus, where tremor is all that it can control. However work is being done with the electrode being placed on the sub-thalamic nucleus. This could help control other Parkinsonian symptoms, including dyskinesia and dystonia.

Dr. Heit feels that this will be the next big breakthrough in treatment for Parkinson's.... This came to me as a surprise, but perhaps it should not have. Using the sub-thalamic nucleus as a target has been mentioned frequently in Joe Bruman's report indices. It was also discussed at length by Margie Swindler and others after a Kansas City Symposium about this time last year [1997].

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.
3. STN Implant: Stimulating electrode is placed in the subthalamic nucleus (this is distinct from the thalamus). Controls dyskinesias, slowness, lack of movement, tremor.