There is currently no proven cure for Parkinson’s disease. However, medications and surgery can often provide patients with relief from the symptoms caused by the disease. There are drugs that work to increase the level of dopamine in the brain, mimic dopamine, or slow the breakdown of dopamine. Levodopa, for example, are converted into dopamine after crossing the blood-brain barrier. There are also drugs that affect neurotransmitters in the body to ease some of the symptoms of the disease. Anticholinergic drugs, for example, interfere with the uptake or production of acetylcholine.
Acetylcholine is a neurotransmitter that is associated with tremors and stiffness of the muscle when its levels exceed those of dopamine. Most medications prescribed for Parkinson’s disease help control its non-motor symptoms. Ryan J. Uitti enumerated three types of surgery that are currently available for treating Parkinson’s disease: lesioning, stimulation, and grafting. Lesioning involves an irreversible destruction of hyperactive neurons while stimulation involves a reversible “stunning” of hyperactive neurons.
On the other hand, grafting involves the transplantation of neurons, cells or trophic factors. It is apparent that some areas of the brain with extrapyramidal pathways such as the Gpi and STN demonstrate excessive neuronal activity in Parkinson’s disease. Uitti explained that the surgical treatments are effective as it minimizes the “overactivity, through permanent destruction (with lesioning) or temporarily disabling neurons with electrical ‘jamming’(by stimulation)” which results in the improvement of control of movement through the extrapyramidal pathways.
The ventral intermediate nucleus in the thalamus, for example, may be performed with lesioning or stimulation which may improve tremors on the contralateral side of the patient’s body but paresthesia can occur with stimulation. Lesioning and stimulation in the internal globus pallidus in the medial pallidum also improves tremor as well as rigidity, bradykinesia and levodopa-induced dyskinesia but offers little benefit for instability. Stimulation in the subthalmic nucleus improves all primary symptoms of Parkinsonism and grafting in the caudate and putamen in the striatum can improve tremor, rigidity and bradykinesia.
Uitti further explained that 90 percent of patients who undergo thalamic stimulation for unilateral limb tremor can expect improvement with complete or near resolution of tremor but needs to continuous stimulation for the benefit to be maintained. However, the benefits could only last for up to eight years regardless if stimulation is continued or not. Benefits following surgery in the pallidum, on the other hand, appear to last for at least three years but may only reduce the severity of rigidity and bradykinesia by an average of 30 percent.
This may seem to be a small benefit if not for the fact that most anti-Parkinsonian medications could only improve the patient’s condition by as much as 20 percent. While these surgeries may provide relief for the patients suffering from Parkinson’s disease, Uitti warns that two of these treatments—lesioning and stimulation—“reduce function within the target regions of the brain. ” Furthermore, severe adverse effects such as hemorrhage causing stroke and death typically occur during or immediately after surgery. Grafting, however, “seeks to supplement function by providing a source of neurotransmitters. ”