Parkinson's Disease: Everything You Need to Know
The first description of Parkinson’s disease was made by the British physician James Parkinson in 1817. It arose as a result of observing six patients with the typical symptoms of the disease, which he called ‘agitant paralysis’. Later, the famous French neurologist Charcot gave it its current name.
Parkinson’s disease is the most prevalent motor neurodegenerative disease worldwide. Currently there’s no cure, but there are several types of treatments that can relieve some of the symptoms and slow the disease’s progress.
What is Parkinson’s disease?
Parkinson’s disease is a chronic and progressive disease, which means that it worsens as the disease progresses. Its progress is slow and is characterized by motor and non-motor symptoms.
It’s the most common neurodegenerative disorder after Alzheimer’s, and age is the most important risk factor for its appearance. The symptoms of the disease are a consequence of the loss of neurons – mainly the ones belonging to the nerve pathway of the substantia nigra.
Parkinson’s disease is one of the most common types of degenerative diseases worldwide. Approximately 10 million people in the world suffer from it; it affects 1% of the people over 60 years of age and 4-5% of those over 85 years of age.
The EPINEURO study found that there are 4.7 affected people per thousand inhabitants in Latin America. This disease occurs more frequently in men than in women, in a ratio of 1.5: 1.
The average life expectancy in patients with Parkinson’s disease is 11-15 years, with pneumonia (11-28%), cardiovascular diseases (12-19%), and cancer (12-14%) being the main causes of death.
In patients between 25 to 39 years of age, life expectancy can be up to 38 years, while, in those over 65, it’s only five years. The quality of life of the patient progressively deteriorates and creates a great burden for their caregivers, which is increased by:
- Sleep, cognition, and behavior disorders
- Duration of the disease and the disability it generates
How this disease occurs
Experts don’t know how long the disease is present before symptoms start to appear. Two phases have been identified:
- The presymptomatic phase, which occurs at the time of exposure of the individual, with or without hereditary burden.
- The symptomatic phase includes signs and symptoms of the disease, and the clinical manifestations are directly related to the severity of the neuronal loss in the substantia nigra.
In addition, the progression of the disease is also determined by this loss of neurons. Dopamine is estimated to reduce by between 70 and 90% when clinical manifestations occur. However, 60 to 70% of the dopaminergic neurons have already been lost when the first symptoms appear.
There’s evidence that some non-motor symptoms can appear even before motor symptoms, such as autonomic symptoms (constipation) and hyposmia (decreased sense of smell).
- Living in the countryside
- High iron intake
- Chronic anemia
- Severe head trauma
- Jobs with high cognitive complexity
On the other hand, the main protective factors are:
These factors, together with genetic factors, could explain most cases of Parkinson’s disease, as genetic causes alone aren’t enough for the disease to manifest itself.
Symptoms and signs
Parkinson’s disease is highly variable, as each patient has different symptoms and a different trajectory. There aren’t any factors that allow us to predict the course of the disease.
It’s clinically manifested by motor symptoms, which are:
- Bradykinesia (slow movements)
- Stiffness and postural instability
Other symptoms are small and illegible writing and difficulty in performing fine tasks. These symptoms usually start on one side of the body and gradually affect the opposite side.
The most common initial symptoms are hand tremors while at rest. However, even though this is the most visible symptom, it isn’t the most disabling. Stiffness is a passive resistance to movement, both of the flexor and extensor groups, and throughout the entire range of motion.
Other non-motor symptoms are:
- Autonomic disorders (loss of sphincter control)
- Sexual dysfunction
- Sleep disturbances
Treatment of Parkinson’s disease
Levodopa remains the most effective drug, although, after months or years, the therapeutic effect diminishes. There are some characteristics of levodopa that can cause controversies as to when to start treatment.
When it’s started too early, adverse effects can appear, such as dyskinesias (involuntary movements) and motor fluctuations. Because of this, there’s no current agreement regarding when to start the treatment or the dose to prescribe.
The treatment of Parkinson’s disease has the following objectives:
- Improving symptoms and signs of the disease (symptomatic treatment)
- Stopping or slowing the progression of the disease
- Reversing the underlying pathology
- Preventing and detecting adverse effects
Prognosis of Parkinson’s disease
According to News Medical magazine, “Parkinson’s disease has a variable prognosis, which depends both on the genetics of the patient and the treatment they receive.”
Untreated, Parkinson’s disease will obviously get worse as the years go by. It can lead to deterioration of all brain functions and early death. However, life expectancy is almost normal in the majority of treated patients.
However, complications associated with the disease are what can reduce life expectancy. There are several scales that can be used as tools to understand the progression of the disease.
The most widely used scales focus on motor symptoms. The general use scales are:
- Hoehn and Yahr rate the symptoms of the disease on a scale of 1 to 5. On this scale, depending on the difficulties of a person, the stages classified as 1 and 2 represent the early stage; 2, 3, 4 and 5, the advanced scenario.
- The Parkinson’s disease scale (UPDRS) is more comprehensive than the Hoehn and Yahr scale. It takes into account cognitive difficulties, the ability to carry out daily activities, behavior, mood, and complications of the treatment, along with movement symptoms.
- Dauer, W., & Przedborski, S. (2003). Parkinson’s disease: Mechanisms and models. Neuron. https://doi.org/10.1016/S0896-6273(03)00568-3
- Blochberger, A., & Jones, S. (2011). Parkinson’s disease clinical features and diagnosis. Clinical Pharmacist. https://doi.org/10.1136/jnnp.2007.131045
- Tekkalaki, B., Kar, S. K., Saha, R., & Mohapatra, S. (2016). Depression in Parkinson’s disease. In Journal International Medical Sciences Academy. https://doi.org/10.1201/b12948
- Bose, A., & Beal, M. F. (2016). Mitochondrial dysfunction in Parkinson’s disease. Journal of Neurochemistry. https://doi.org/10.1111/jnc.13731