Named after English physician Dr James Parkinson, who first described the disease as the “shaking palsy” in 1817, Parkinson’s disease is a degenerative condition of the central nervous system, characterised by both motor symptoms (tremor, rigidity and impaired movement) and non-motor symptoms (problems sleeping, loss of sense of smell, speech and swallowing problems, cognitive impairment, depression and anxiety).
There is currently no cure for Parkinson’s disease although some of the movement symptoms can be alleviated.
There are currently about 80,000 Australians living with Parkinson’s disease. It is usually diagnosed around the age of 65, but of those who contract the disease, one in ten will be diagnosed before they are 45. Men are slightly more at risk of developing Parkinson’s than women.
What causes Parkinson’s disease?
The exact cause of Parkinson's disease is unknown. The most likely situation scenario is that either exclusively genetic causes or exclusively environmental causes are responsible for the disease in some patients, while a combination of environmental and multiple genetic factors contribute to the disease in the majority of patients.
The movement related symptoms of Parkinson’s disease result from the progressive degeneration of neurons, or brain cells, in the midbrain. Neurons in the part of the brain that control co-ordinated movement release a neurotransmitter called dopamine. Dopamine stimulates motor neurons, those nerve cells that control the muscles.
When dopamine production is depleted, the motor system nerves are unable to control movement and coordination. Parkinson’s disease patients have lost 80% of the relevant dopamine-producing cells by the time their symptoms appear.
What are the symptoms of Parkinson’s?
Motor-Symptoms: Initially, symptoms are mild and often located on one side of the body. Although the rate of progression varies between individuals, the symptoms become more pronounced and spread to other parts of the body:
- Tremor (shaking) - this often occurs in the hands, fingers, forearms, foot, mouth and chin. Tremors typically take place when limbs are at rest
- Rigidity (muscle stiffness) – this often produces muscle pain that is increased during movement
- Bradykinesia - slowness in voluntary movement such as standing up, walking and sitting down
- Difficulty with balance - this occurs due to the loss of reflexes that help posture. Falling is common
- “Parkinson’s gait” - this common walk of a Parkinson’s patient includes a shuffling gait, drooped shoulders, lack of arm swing, head faced down and leaning backwards or forwards unnaturally. It is difficult to initiate walking and pausing mid-stride is common
- Micrographia (small handwriting)
- Lethargy and depression
Non-Motor Symptoms: Doctors are increasingly recognizing the presence and effects of other symptoms of PD that are sometimes called "non-motor symptoms" or "dopamine-non-responsive." These symptoms are common and can have a major impact on Parkinson’s patients. They can include:
- Cognitive impairment – decline in ability to multi-task and/or concentrate and potentially decline in intellectual functioning
- Mood disorders – depression and anxiety
- Problems sleeping – REM Sleep Disorder, where individuals act out their dreams
- Hyposmia – loss of sense of smell
- Speech and swallowing problems
- Unexplained pains, drooling and low blood pressure when standing
How is Parkinson’s diagnosed and managed?
There are currently no laboratory tests to diagnose Parkinson’s disease definitively. A thorough neurological examination, including testing of reflexes, muscle strength and coordination is given, along with other tests, such as magnetic resonance imaging (MRI) and blood tests, to rule out the possibility of other diseases. As there is currently no cure for Parkinson’s, the symptoms are managed with a variety of treatments including drug and physical therapy.
Drug therapy aims to overcome the problem of depleted dopamine stores in the brain. Different drugs have different actions: some mimic the action of dopamine, some prevent further depletion and some enhance the action of the remaining dopamine stores. A neurologist will prescribe the treatment and dosage appropriate to the patient as severity and type of symptoms vary greatly between individuals.
In severe cases, neurosurgery may be necessary to relieve symptoms. Lesions are made on certain parts of the brain to interrupt involuntary movement. Deep brain stimulation, where an electrode is implanted in the affected area of the brain, may also help alleviate symptoms.
What research is Garvan doing in this area?
Garvan Institute researchers are investigating:
- The mechanisms behind cell degeneration – how certain pesticides, toxins and genes (such as the alpha-synuclein gene) cause Parkinson’s disease, so as to target therapy or a cure
- Large scale genomic analyses, to identify the multi-genetic contributions to the disease
- The mechanisms behind the release and control of dopamine in the brain. Once the various mechanisms are known, we can develop a therapeutic approach to treat the disease and restore movement control
- How we can harness the brain’s own adult stem cells (which normally function to repair injury to the brain and make new nerve cell connections) to help treat Parkinson’s disease, as well as other neurodegenerative conditions
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