History and incidence of Parkinson’s disease
Parkinson's disease was first formally recognized and its symptoms documented in 1817 in an essay on the Shaking Palsy by the British physician Dr James Parkinson. The associated biochemical changes in the brain of the patients were identified in the 1960s. After Alzheimer’s disease, Parkinson disease is the most common neurodegenerative disease. An estimated 4 to 6 million people have been diagnosed with Parkinson's disease. There are over 1.5 million in China alone. The greatest prevalence is the U.S.A., with between 100 and 250 cases per 100,000.
Pathophysiology of the condition
Parkinson disease is actually caused by the damages to the dopamine pathways in our brain. There are four major dopamine pathways in the brain;
- The nigrostriatal pathway, which mediates movement and is the most conspicuously affected in early Parkinson's disease. The mesocortical,
- The mesolimbic,
- The tuberoinfundibular.
These pathways are associated with:
- volition and emotional responsiveness;
- desire,
- initiative,
- reward;
- sensory processes
- maternal behavior
The reduction in dopamine along the non-striatal pathways is the likely explanation for much of the neuropsychiatric pathology associated with Parkinson's disease.
Symptoms of Parkinson’s disease
Since Parkinson disease primarily affects movement, in most cases, we are talking about motor symptoms. However, there are many other non-motor symptoms such as various mood, behavior, thinking, and sensation disorders.
Motor symptoms
- tremor
- rigidity
- bradykinesia / akinesia
- postural instability
- Shuffling: gait is characterized by short steps, with feet barely leaving the ground, producing an audible shuffling noise. The patients tend to trip over small objects.
- Decreased arm swing
- Stooped, forward-flexed posture. In severe forms, the head and upper shoulders may be bent at a right angle relative to the trunk
- Festination: a combination of stooped posture, imbalance, and short steps. It leads to a gait that gets faster progressively, often ending in a fall.
- Gait freezing: characterized by inability to move the feet, especially in tight, cluttered spaces or when initiating gait.
- Dystonia: abnormal, sustained, painful twisting muscle contractions
- Hypophonia: soft, hoarse, and monotonous speech.
- Festinating speech: excessively rapid, soft, poorly-intelligible speech.
- Drooling: most likely caused by a weak, infrequent swallow and stooped posture.
- Dysphagia: impaired ability to swallow
- masked facies
- difficulty rolling in bed or rising from a seated position;
- micrographia (small, cramped handwriting);
- impaired fine motor dexterity and coordination;
- impaired gross motor coordination;
- Overall loss of accessory movements
Non-motor symptoms
Mood disturbances
- depression
- anxiety or panic attacks
- apathy or abulia
Cognitive disturbances
- slowed reaction time
- executive dysfunction
- dementia
- memory loss
- medication effects
Sleep disturbances
- Excessive daytime somnolence;
- Initial, intermediate, and terminal insomnia;
- Disturbances in REM sleep
Sensation disturbances
- impaired visual contrast sensitivity
- dizziness and fainting
- impaired proprioception
- loss of the sense of smell
- pain
Autonomic disturbances
- oily skin and seborrheic dermatitis;
- urinary incontinence
- constipation and gastric dysmotility:
- altered sexual function
Possible causes of Parkinson’s disease
No one really knows exactly what the main cause of Parkinson’s disease is. Experts have determined that many of the signs and symptoms of Parkinson's disease develop when certain nerve cells in an area of the brain called the substantia nigra are damaged or destroyed, but what is the trigger?
Environmental factors
Several studies have proven that people with unusual exposure to herbicides and pesticides are more likely to develop Parkinson's disease.
Medications
A number of drugs taken for long periods of time or in excessive dosages can cause symptoms of Parkinson's disease. These include medications such as haloperidol (Haldol) and chlorpromazine (Thorazine), Metoclopramide (Reglan, Metoclopramide HCL). Patients should understand that these medications do not cause Parkinson's disease, but the similar symptoms that disappear when the drugs are stopped.
Risk factors for developing Parkinson’s disease
Age
Age is one of the main risk factors for Parkinson's disease.
Heredity
Having one or more close relatives with Parkinson's increases the chances that you'll also develop the disease, although your risk is still less than 5 percent.
Sex
Men are more likely to develop Parkinson's disease than women are.
Reduced estrogen levels
Several studies done recently have proven that reduced estrogen levels may increase the risk of developing Parkinson's disease. This means that menopausal women or the ones who have had hysterectomy done may be at a higher risk.
Diagnosis of Parkinson’s disease
There are big problem with the diagnosis of Parkinson’s disease is that there are no definitive tests. The disease is paricularly hard to diagnose in it’s early stages. All the cardinal symptoms of Parkinson may be dismissed as the effects of aging.
A diagnosis of Parkinson's disease is based on three things:
- medical history,
- observations of signs
- neurological examination, which includes an evaluation of walking, coordination and some simple tasks of dexterity
After a thorough neurological exam and medical history, the neurologist may order CT scan or MRI scan to meet the other criterion for a diagnosis of Parkinson's disease and rule out disorders that produce similar symptoms.
Complications if left untreated
Depression
Nearly 50% people with Parkinson's disease develop depression. In some cases, depression may occur months or even years before Parkinson's disease is diagnosed.
Dementia
Some people with Parkinson's disease develop dementia, a condition that can include memory loss, impaired judgment and personality changes.
Difficulty chewing and swallowing
The muscles patients use to swallow may be affected, making eating and speaking more difficult.
Urinary problems
It is proven that Parkinson's disease may cause either urinary incontinence or urine retention.
Constipation
Many patients develop constipation because the digestive tract works more slowly.
Sleep problems
Although the right cause still remains unclear, people with Parkinson's disease often have trouble falling asleep and may wake up frequently throughout the night.
Sexual dysfunction
Decrease in sexual desire is a very common symptom.
Treatment for Parkinson’s disease
Unfortunately, there is no cure for Parkinson's disease. Treatment centers on the administration of medications which relieve the symptoms.
Physical treatment
Physical therapy can be extremely helpful for people with Parkinson's disease, both in the early stages and later, as the disease progresses. It can help improve mobility, range of motion and muscle tone. Although specific exercises can't stop the progress of the disease, improving muscle strength can help you feel more confident and capable.
Medications
Levodopa
Levodopa is a medication that has been considered the gold standard drug therapy for Parkinson's disease. It is a natural substance found in plants and animals. It's a precursor to dopamine that, when given to people with Parkinson’s is converted into dopamine.
Treatment with dopamine isn't possible, because it doesn't cross the body's blood-brain barrier.
Dopamine agonists
These medications mimic the effects of dopamine in the brain and cause neurons to react as though sufficient amounts of dopamine were present.
Anticholinergics
These drugs were the main treatment for Parkinson's disease before the Levodopa was found! They help control tremor in the early stages of the disease.
Surgery
Thalamotomy
It involves the destruction of small amounts of tissue in the thalamus
Pallidotomy
During this procedure, an electric current is used to destroy a small amount of tissue in the pallidum (globus pallidus), a part of the brain responsible for many symptoms of Parkinson's disease.
Deep brain stimulation
Deep brain stimulation consists of a pacemaker which transmits electric impulses through a wire to tiny electrodes inserted deep within the brain.