There are two main surgical procedures, deep brain stimulation and lesioning. Each procedure has three possible surgical targets in the brain: the thalamus, the globus pallidum internus (GPi), and the subthalamic nucleus (STN).
- Deep brain stimulation (DBS): Uses implanted electrodes to stimulate either the STN or the GPi. The electrical stimulation that these electrodes produce disrupt the abnormal brain activity which causes movement problems and so improves these symptoms. The stimulator can be adjusted or switched off as necessary.
- Lesioning: Delivers an electrical current to a targeted area of the brain (pallidotomy, thalamotomy and subthalamotomy) which heats and destroys or lesions that area, usually around the size of a pea. This is not reversible and its effects cannot be switched on and off in the way that DBS can be.
- Gamma knife surgery: This technique is not commonly used.
There are a number of other surgical procedures currently being researched but at present, these are largely experimental and remain a source of hope for the future. These fall into two main categories:
Neural transplants : Replaces dead and dying dopamine-producing cells in the brain with transplanted tissue in the hope that it will help to raise the dopamine levels in the brain to a more normal level, and help reduce Parkinson’s symptoms. Techniques being researched are:
- stem cells implants: Each of the cells in our bodies contains the same Deoxyribonucleic acid (DNA) but only part of this is ‘differentiated’ or ‘turned on’ according to the part of the body the cell is to be used for. Stem cells are those which have all our genetic information stored in their DNA but as yet they are ‘undifferentiated’, that is they are not yet committed to becoming a specific kind of cell. They have the potential to develop into any type of cell in the body, providing exciting possibilities in treating all kinds of illnesses. Stem cells may be found in various parts of the body, for example embryonic tissue, the developing nervous system, the adult nervous system and bone marrow
- retinal pigment epithelial cell transplants: These cells are derived from tissue at the back of the eye which produce and release dopamine. Initial trials have shown some promise so further trials are now being carried
- xenografts, i.e. transplants of tissue from one species to another: Results have been mainly negative to date, essentially due to problems with the rejection of implanted cells by the immune system. Research is ongoing.
- adrenal gland cell grafts: Largely abandoned because of poor results and the complicated nature of this type of surgery.
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brain infusions: The infusion of chemicals into the basal ganglia, the part of the brain affected by Parkinson’s, in the hope of encouraging the damaged cells to rejuvenate and produce more dopamine.
