Parkinson's disease is a slowly progressing disease of the nervous system that causes people to lose control over their muscles.
About 1 in 250 people over the age of 40, about 1 in 100 people over the age of 65, and about 1 in 10 people over the age of 80 are affected by Parkinson's disease. Although the average age of onset is 57,
Parkinson's occasionally appears in childhood. Men are more likely to develop Parkinson's than women.
Parkinson's is not a fatal condition. However, the end stage of the disease can lead to pneumonia, choking, severe depression, and death.
Although the brain cells that control movement (the motor neurons) are located along the top of the brain, they rely on a chemical called dopamine that's manufactured in an area of the brain called the substantia nigra.
In Parkinson's, dopamine-producing cells in the substantia nigra are lost. In most cases, we don't know why. Primary Parkinsonism is the diagnosis in the majority of cases where the doctor doesn't know why these cells are dying. One thing researchers do know is that in the majority of people with Parkinson's disease, a protein called synuclein accumulates to form protein deposits called Lewy bodies. Researchers believe that Parkinson's disease is a late complication of protein accumulation, where the protein can accumulate in other areas of the brain, spinal cord, peripheral nerves, and in the intestinal tract.
Secondary Parkinsonism is due to some disease (e.g., nervous system conditions, heart disease, brain tumours, viruses) or chemical interfering with or damaging dopamine-producing cells in the brainstem. The most common cause is side effects of medication for other problems. Medications that can cause secondary Parkinsonism include:
- haloperidol* and other medications used to treat hallucinations
- metoclopramide (an antinausea medication)
Less common causes of secondary Parkinsonism include poisoning by carbon monoxide or manganese (a type of mineral), lesions and tumours in the brainstem, and a rare illicit drug called N-MPTP. An outbreak between 1918 and 1924 of a disease called von Economo's encephalitis left thousands of people across North America with Parkinson's.
A number of genetic mutations have recently been identified, suggesting that Parkinson's may run in some families. Around 10% of people affected have a family history of the disease, however, a major US twin study suggested that environment plays a larger role than inheritance. The current consensus is that genetic factors are dominant only in Parkinson's that appears before age 50.
Symptoms and Complications
The main symptoms of Parkinson's disease are:
- tremor, shaking, or trembling
- slowed movement
- stiff or rigid arms, legs, and trunk
- balance trouble that can lead to falls
Tremors only appear at rest and not when the person is making purposeful movements. Later, the arms and legs may be affected. About 15% of people with Parkinson's don't have tremors; rather, they find their limbs or other areas turning stiff or rigid. Most people, however, have both. The rigidity becomes worse as the disease progresses, making movement difficult.
Slowed movement is another symptom of Parkinson's disease. People may also experience trouble starting movement (e.g., starting to walk) and will move much slower than normal. When balance reflexes become impaired, it makes it difficult to turn quickly or negotiate narrow corners and doorways.
Other symptoms that are common in Parkinson's (though no one person will have all of them) include:
- abnormal walking
- decreased arm swing
- excessive salivation
- feelings of depression or anxiety
- increase in dandruff or oily skin
- lack of facial expression (hypomimia)
- less frequent blinking and swallowing
- lowered voice volume (hypophonia)
- slight foot drag
- small cramped handwriting (micrographia)
- stooped posture
- trouble sleeping
- difficulty urinating or urinary incontinence
- decreased sense of smell
- dizziness when standing
- decreased sense of smell
- muscle aches
Depression is common in people with Parkinson's. Psychotic symptoms, such as visual or auditory hallucinations, may occur in up to 50% of cases. People with Parkinson's also run a higher risk of developing dementia, which often results in problems with memory or concentration similar to what is seen in Alzheimer's disease.
Making the Diagnosis
There's no definitive test for Parkinson's disease. Diagnosis is based purely on the symptoms and a physical examination. The fact that trembling in Parkinson's is at its worst when the muscles are resting distinguishes it from other kinds of tremors. People with Parkinson's also tend to have an odd gait or walk, which is stooped and shuffling with little or no spontaneous arm swinging. Your doctor may orders tests (e.g., blood tests) to rule out other medical causes of your symptoms.
Treatment and Prevention
There is no cure for Parkinson's disease. And because treatment is aimed at reducing the symptoms, every treatment plan is individualized. Treatment is usually recommended as soon as symptoms are interfering with daily life. Together with your doctor, you will come up with a treatment plan that works best for you.
Treatment of Parkinson's disease can involve medications, surgery, and lifestyle changes.
Medications used in the treatment of Parkinson's disease help to increase dopamine levels in the brain or mimic the action of dopamine. Dopamine can't be given directly because it can't cross the blood-brain barrier, a lining that insulates the brain from the rest of the body. However, a medication called levodopa does get into the brain, where it is converted to dopamine, which is then used to replace the missing dopamine and improve control of movements.
It was once thought that treatment with medications such as levodopa should be delayed because of the concern that the medication becomes less effective after about 2 to 5 years of treatment. There was also concern about people taking levodopa developing alternating bouts of disabling stiffness and uncontrolled movements called dyskinesias. However, recent studies have shown these concerns to be unfounded and that early treatment is needed to help with physical and mental functioning.
Levodopa is often given with other medications such as carbidopa, benserazide, or entacapone that allow for smaller doses of levodopa to deliver more benefit.
Other medications for Parkinson's include bromocriptine, pramipexole, and ropinirole, which belong to a group of medications called dopamine agonists. Rather than replacing dopamine, these medications directly stimulate the areas that usually respond to dopamine. Other medications that may also be used include anticholinergic medications (e.g., benztropine), monoamine oxidase B inhibitors (e.g., rasagiline, selegeline, safinamide), and amantadine.
For people who have tremors or other movement symptoms that are no longer responding to treatment, or have disabling dsykinesias caused by medications, there are surgical options.
Deep brain stimulation involves sending an electrical current through a wire to the areas of the brain that control movement (thalamus, subthalamic nucleus, globus pallidus). This helps to block the abnormal signals produced in Parkinson's disease. Research continues to evaluate which areas of the brain are the best targets for deep brain stimulation. Research is now focusing on treatments that protect the brain. Regular exercise and physical therapy can help stave off loss of motor control. Keeping active and eating a good diet are vital in the management of Parkinson's disease. People with Parkinson's disease should eat a high-fibre diet and drink plenty of fluids because both Parkinson's and some of the medications used for treatment can cause constipation. Your doctor may recommend supplements and laxatives to keep you regular.
Make sure that you have regular follow-ups with all of your health care providers, such as your doctor, physiotherapist, occupational therapist, speech therapist, and nutritionist.