Parkinson's Disease: Causes, Symptoms, Investigations, Treatment
Parkinson's disease is a nervous system disorder, which affects a person's movements and continues to gradually worsen.1 It is slow of onset and starts with a barely obvious tremor in only one hand. Tremor is a common and well known sign of Parkinson's disease2; however, this condition also causes slowness of movement or stiffness of muscles. In the initial stages of Parkinson's disease, patient's face may have little or no expression and there may absence of swinging of the arms when walking. The speech also becomes slurred or soft. As Parkinson's progresses, the symptoms also worsen over the time.
There is no cure for Parkinson's disease; however, medications significantly improve the symptoms. Surgery is done in some cases to regulate specific areas of the brain and improve the symptoms.
Causes & Risk Factors Parkinson's Disease
Parkinson's disease occurs as result of gradual degeneration and death of certain neurons or nerve cells. Symptoms are produced because of lack of production of dopamine, which is a chemical messenger in the brain. As the dopamine levels decrease, there is abnormal activity in the brain causing the signs and symptoms of Parkinson's disease.
The exact cause of Parkinson's disease is not known, there are many factors which can lead to it, such as:
- Exposure to certain environmental factors or toxins increases the risk of Parkinson's disease.
- There are specific genetic mutations which can lead to Parkinson's disease; however, it is not that common, only in rare cases where multiple family members are affected by Parkinson's disease. There are certain gene variations which are thought to increase the risk of Parkinson's disease.
- Parkinson's is more common in middle aged or older individuals. Young adults are rarely affected by it.
- Women are less likely to develop Parkinson's disease than men.3
- Having a family history of Parkinson's disease leads to increased risk for developing this disease.
- Continuous exposure to toxins, such as pesticides and herbicides, increases the risk of Parkinson's disease.
Signs & Symptoms of Parkinson's Disease
The symptoms of Parkinson's disease vary from patient to patient. Initial symptoms can be very mild and patient may not notice them. Symptoms usually start on one side of the body and remain worse on the same side, even after the symptoms start affecting both the sides of the body.
- Tremor is the most common indication of Parkinson's and is commonly first noticed in a hand or fingers. Patient may have a backwards-and-forwards rubbing of the forefinger and thumb, also known as "pill-rolling tremor." Another characteristic sign of Parkinson's disease is shaking of the hand when it is at rest.
- Muscle stiffness or rigidity can occur in any part of the body and causes pain and limits the patient's range of motion.
- Bradykinesia or slow movements is another symptom of Parkinson's which reduces the patient's movement ability and makes simple tasks time-consuming and difficult to perform. Patient's footsteps also become smaller and patient tends to drag his/her feet when walking. Patient also finds it difficult to get out of a chair.
- Loss of involuntary movements, such as smiling, blinking, swinging the arms when walking or absence of gestures when talking.
- There are balance problems and posture impairment and the patient may start stooping.
- Speech changes, such as the patient may slur, speak quickly, softly, or hesitate before speaking. The speech of the patient also becomes monotonous and loses its normal inflections. A speech-language pathologist helps in dealing and improving with these speech problems.
- There are writing changes, such as the patient may find it difficult to write and the writing appears smaller.
Medications help in markedly reducing most of the above symptoms and they work by either substituting or increasing the brain chemical dopamine, which helps with symptoms, as patients with Parkinson's disease will have the neurotransmitter, dopamine, in low concentrations.
Investigations for Parkinson's Disease
There is no specific test to diagnose Parkinson's disease. Medical history with physical and neurological exam is conducted by the doctor. Some other tests may be done to rule out medical conditions which may be causing symptoms similar to Parkinson's disease. Parkinson's disease medication, such as carbidopa-levodopa is given, which after taking, if causes reduction in the symptoms confirms the diagnosis of Parkinson's disease. Sufficient dose must be taken for benefit, as low dosages for a day or two do not cause beneficial response. The medicine must be taken on an empty stomach about an hour before the meals for optimum response.
In some cases, it takes time for diagnosing Parkinson's disease. Patients should work with their doctors and follow regular appointments with neurologists who are trained in movement disorders to assess their condition and symptoms which help in diagnosis of Parkinson's disease.
Treatment for Parkinson's Disease
There is no cure for Parkinson's disease. However, medications significantly help in controlling the symptoms. Surgery may be advised in some cases.
Medications for Parkinson's Disease
Medications help in managing the tremors, problems with movement and walking by substituting or increasing the dopamine in the brain. However, as dopamine cannot enter the brain, it cannot be given directly. Patient experiences significant improvement in their symptoms after starting on medicines for Parkinson's disease. However, over a period of time, the improvement in the symptoms diminishes even though the symptoms continue to be quite well controlled.
Medications prescribed for Parkinson's disease include:
- Carbidopa-levodopa is the most effective medicine in Parkinson's disease and levodopa gets converted into dopamine after passing into the brain. It is given in combination with carbidopa, which prevents premature conversion of levodopa into dopamine outside the brain, which in turn prevents or decreases the side effects such as nausea. Other side effects include lightheadedness or nausea. As time goes on, the benefit of levodopa diminishes and tends to wax and wane. Patients taking high doses of levodopa also have involuntary movements, such as dyskinesia. For this reason, the dosage of the medicine will be adjusted or decreased.
- Dopamine agonists mimic the effects of dopamine in the brain and do not convert into dopamine. When compared to levodopa, they are not as effective in treating the symptoms; however, their effect lasts longer and it can be used in conjunction with levodopa to manage or regulate the wax and wane effect of levodopa. Some of the examples of dopamine agonists include pramipexole, ropinirole, apomorphine and rotigotine. Side effects of dopamine agonists include lightheadedness, nausea, swelling, hallucinations, sleepiness and compulsive behaviors, such as gambling, hypersexuality and eating. Consult the doctor immediately if the patient is taking these medications and behaving in an uncharacteristic manner.
- Catechol O-methyltransferase (COMT) inhibitors include Entacapone which is the main medication in this class. Entacapone blocks an enzyme, which breaks down dopamine and slightly increases the effect of levodopa therapy. Side effects include: increased risk of dyskinesia from enhanced effect of levodopa and diarrhea. Tolcapone is another COMT inhibitor which causes liver failure and serious liver damage and is rarely prescribed.
- MAO-B inhibitors include medications, such as selegiline and rasagiline. These medicines inhibit the brain enzyme monoamine oxidase B (MAO-B) and help in preventing the breakdown of dopamine in the brain. (MAO-B) metabolizes dopamine and side effects of this medicine include headaches and nausea. The risk of hallucinations is increased when this medicine is added to carbidopa-levodopa. These medications are also not used in combination with antidepressants and certain narcotics as they can cause dangerous and rare reactions. So, it is advisable to check with your doctor before starting to take any additional medications with MAO-B inhibitors.
- Anticholinergics have been in use for Parkinson's disease for many years to help in controlling the tremors of Parkinson's. Some of the examples of anticholinergic medications include benztropine and trihexyphenidyl; but their benefits are less and side effects include confusion, impaired memory, hallucinations, dry mouth, constipation and impaired urination.
- Amantadine is prescribed for early-stage Parkinson's disease and provides short-term relief from its symptoms. Amantadine can also be given alongside carbidopa-levodopa therapy in the later stages of Parkinson's disease where it will help in controlling dyskinesias or involuntary movements, which are induced by carbidopa-levodopa. Side effects include swelling in the ankles, purple mottling of the skin and hallucinations.
Surgical Procedures for Parkinson's Disease
- Deep brain stimulation or DBS is a procedure where electrodes are implanted in a specific area in the brain and these are connected to a generator, which is implanted in the chest. Electrical pulses are sent through them to the brain, which help in reducing the symptoms of Parkinson's disease. The settings need to be adjusted by the doctor according to the condition. Risks of surgery include stroke or brain hemorrhage and infection.
- Patients who are experiencing problems with this system or are having complications from stimulation need adjustment of the settings or need to replace certain parts of the system. Deep brain stimulation is done in the patients with advanced stage Parkinson's disease and who do not respond well to the levodopa therapy. Deep brain stimulation also helps in stabilizing the fluctuations of the medication and also helps in reducing the dyskinesias, tremors, muscle rigidity and improves the slowness of the movement. Deep brain stimulation is also beneficial in the inconsistent responses to levodopa therapy and in controlling dyskinesias, which do not respond to adjustments in medications. However, other than tremors, Deep brain stimulation is not helpful in problems which do not respond to levodopa. Deep brain stimulation can control tremor even if it is not responsive to levodopa therapy. Deep brain stimulation also provides benefit to persistent symptoms of Parkinson's; however, it does not prevent the progression of the disease.
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