Instead, it is suspected that Parkinson’s usually results from
the combination of a genetic predisposition and an as yet unidentified
environmental trigger (www.pdf.org, December page 3 2000). For early treatments
of Parkinson’s disease, extracts from the belladonna plant were found to help
relax stiffened muscles and to quiet tremors and were used in therapy until
after World War II, when a number of similarly acting drugs came into use.
Discovery of the brain dopamine deficiency in parkinsonian patients - reported
in 1960 by researchers at the University of Vienna - brought hope that restoring
the dopamine level might effectively treat the disease. Investigators soon
found, however, that giving dopamine by itself was completely useless: the
substance did not reach the brain because it could not cross the blood-brain
barrier, a protective biochemical mechanism by which the body screens agents
passing from the blood into the central nervous system. Scientists then turned
to levodopa, the substance that is dopamine’s metabolic precursor. Levodopa did
cross the blood-brain barrier and could be quickly metabolized into dopamine. In
1970, levodopa was approved for prescription sale. It was the first major
breakthrough, but side effects are severe nausea and vomiting because the drug
is broken very rapidly in the body, requiring large doses if the substance is to
penetrate the brain. According to the NINCDS Research Program pamphlet, some
patients experienced toxic side effects from these dose levels that were so
severe that the drug had to be discontinued. Researchers soon learned, however ,
that they could greatly reduce dose levels - and thus cut down on side effects -
by giving levodopa in conjunction with a substance that slows its breakdown in
the body. Sinemet, a combination of levodopa and the inhibiting substance
carbidopa, has been available since 1975. Treatments must be fine-tuned to suit
individual patients depending on their symptoms and stage of disease (Tackacs,
Toronto Star). For most Parkinson’s disease patients, the levodopa/carbidopa
page 4 cocktail still stands as the single , most effective therapy available.
Most patients benefit from it: some moderately and some with striking relief
from their symptoms - at least for several years. There are a few other drugs
available that are also prescribed. Symmetrel, which was originally an anti-flu
medication, is thought to block or reuptake dopamine by neurons, or it increases
the release of dopamine by neurons, thereby increasing the supply of dopamine in
the synapses. When its benefits seem to lessen, stopping the drug for a short
time and then reintroducing it seems to provide help once again, according to
some clinicians. Tremors can be controlled by prescribing anticholinergics,
which act to decrease the activity of the balancing neurotransmitter,
acetylcholine. Older patients may not be able to take these drugs because they
tend to cause confusion and hallucination.
Selegiline or deprenyl have been
shown to delay the need for sinemet when prescribed in the earliest stages of
Parkinson’s disease, and they have also been approved for use in later stages to
boost the effects of Sinemet. COMT inhibitors such as tolcapone and entacapone,
represent a new class of Parkinson’s medications. These drugs must be taken with
levodopa so they prolong the duration of symptom relief by blocking the action
of an enzyme which can break down levodopa before it reaches the brain. Like the
symptoms of Parkinson’s disease itself, the side effects of drugs vary from
patient to patient. They may include dry mouth, nausea, dizziness, confusion,
hallucinations, drowsiness, insomnia, and other unwelcome symptoms. Some
patients experience no side effects from a drug, while others have to
discontinue its use because of them. When drugs aren’t working, there’s still
surgery. The most common procedures page 5 are palliodotomys, in which the
surgeon drills through the skull and destroys selected brain cells, and deep
brain stimulation, in which electrodes are implanted in the thalamus and
connected to a pacemaker-like device. In a palliodotomy, there is a possibility
of stroke, partial loss of vision, speech and swallowing difficulties, and
confusion. There aren’t many risks with deep brain stimulation. New,
controversial forms of surgery, called brain tissue implants, are still in
experimental , however, promising results leave researchers hopeful that this
surgery will provide a long-lasting treatment for the disease. Jim Finn, a
recipient of the disease, has had Parkinson’s disease for twenty years. Three
years ago, at age fifty-one, doctors diagnosed him as “end stage” - they could
do nothing more for him. That’s when Finn’s doctor approached him about an
experimental new treatment in which surgeons would implant millions of fetal pig
cells into the brains of Parkinson’s patients. Without hesitation, Finn agreed
to the surgery (Sinha & Zang, pp. 77-81). Finn describes the procedure as going
through a drive-thru: “Buy some burgers, get some surgery.” The whole surgery
actually takes only two-and-a-half hours. Also, patients can be awake the whole
time from the use of local anesthesia. The doctors inject the fetal pig cells
through an injection syringe guided by a halo-shaped frame bolted to the head.
Originally, surgeons used aborted human fetuses to harvest the cells which are
needed, but many considered this unethical. Researchers realized these obstacles
early on, and so focused on using fetal pig cells instead. The results have been
amazing:
