Parkinson’s disease (PD) is a degenerative disorder of the central nervous system. Parkinson motor symptoms are caused by the death of dopamine-generating cells in the substantia nigra midbrain region. It remains unknown what causes the death of these cells.
Signs and Symptoms of Parkinson’s Disease
Parkinson’s disease affects movement, thus displaying motor symptoms, but it can also produce non-motor symptoms. Examples of the latter category include autonomic dysfunction, neuropsychiatric problems, or sensory and sleep issues. Some of these non-motor symptoms can precede motor symptoms.
There are four motor symptoms considered characteristic for Parkinson’s disease: tremor, rigidity, slowness of movement and postural instability. Tremor is the most notorious symptom, as it is the most common and most apparent. Roughly 30 percent of PD sufferers don’t experience tremor at disease onset, but most of them develop this symptom as the disease progresses. This symptom is usually a rest tremor: it reaches its peak when the limb is at rest, and may disappear with voluntary movement and sleep.
Tremor greatly affects most distal part of the limb and it usually appears in only one arm or leg at onset, eventually becoming bilateral as it progresses.
1. Slowness of Movement
Officially called Bradykinesia, slowness of movement is another cardinal symptom of PD and is linked to difficulties of the overall movement process, from planning to initiation to actual execution of a movement. This is often a very disabling symptom in the early stages of Parkinson’s disease. This slowness of movement is not equal for all movements or all instances. The subject’s activity or emotional state can alter the manifestation of bradykinesia. For instance, some patients can barely walk due to this disabling symptom but are able to ride a bicycle. Subjects generally have less difficulty when they receive some external cue.
Rigidity is characterized by stiffness and resistance to limb movement caused by excessive and continuous contraction of muscles. This instance is called increased muscle tone. When tremor accompanies this increased muscle tone, it is believed to cause cogwheel rigidity. In the early stages of the disease, rigidity can often be asymmetrical and usually affects the neck and shoulder muscles first, followed by the muscles of the face and extremities. As Parkinson’s disease progresses, rigidity comes to affect the whole body, significantly limiting one’s ability to move. Rigidity can also be associated with joint pain, marking a common initial manifestation of the disease.
3. Postural Instability
Postural instability is another common symptom in the early stages of Parkinson’s disease. This symptom leads to impaired balance and frequent falls, which in turn may result in bone fractures. Instability is often not found in the initial stages, especially in younger people. Up to 40 percent of patients, meanwhile, may experience falls due to postural instability, while 10 percent may have falls weekly. The number and frequency of falls is associated with the severity of the disease.
4. Other Motor Symptoms
Other recognized motor symptoms of Parkinson’s disease include gait and posture disturbances such as festination, i. e. a forward-flexed posture when walking and rapid steps, speech and swallowing disturbances, small handwriting, still facial expressions, and many other potential symptoms.
PD can cause a number of neuropsychiatric symptoms ranging from mild to severe, including disorders affecting speech, mood, cognition, behavior and thought. In some cases cognitive disturbances appear in the initial stages of the disease and can precede diagnosis. As the disease progresses, such disturbances increase in prevalence. Executive dysfunction is the most frequent cognitive deficit, and it may include difficulties with planning, cognitive flexibility, rule acquisition, abstract thinking, selecting sensory information, and other. Other cognitive difficulties include fluctuations in attention and slowed cognitive speed. Neuropsychiatric symptoms associated with Parkinson’s disease can also affect memory, especially in terms of recalling something learned. When memory recall is aided by certain cues, however, patients do experience improvements in memory function. PD, meanwhile, also comes with video-spatial difficulties.
Compared to the general population, people suffering from Parkinson’s disease are six times more prone to developing dementia. As PD progresses throughout time, the prevalence of dementia increases. Dementia In PD patients is associated with a reduced quality of life, increased mortality rates and a higher probability of needing nursing home care.
Other Symptoms Of Parkinson’s Disease
PD can affect other body functions as well, thus resulting in symptoms other than motor and cognitive. Difficulty sleeping is often associated with the disease, and medications can make it worse. This can result in daytime drowsiness, disturbances of REM sleep, and insomnia.
Meanwhile, changes in the autonomic nervous system can lead to orthostatic hypotension, i.e. a low blood tension when the subject stands up. Other such symptoms include oily skin, excessive sweating, altered sexual function, urinary incontinence, constipation and gastric dysmotility. PD is also associated with a number of eye and vision issues such as decreases blink rate, dry eyes, deficient eye tracking, difficulties in looking upwards, blurred or doubled vision. PD can also cause changes in perception, such as an altered sense of smell, sensation of pain and skin tingling/ numbness. All of these symptoms can manifest even years before the subject is diagnosed with Parkinson’s disease.
Managing Parkinson’s Disease: Treatment Options
While Parkinson’s disease has no cure, patients can get relief from the symptoms through medications, surgery and multidisciplinary management. The main families of drugs used for treating the motor symptoms of PD are levodopa, usually combined with a dopa decarboxylase inhibitor or COMT inhibitor, dopamine agonists and MAO-B inhibitors. One group may prove more useful than the other depending on the stage of the disease.
PD usually has two distinguishable phases: the initial phase, in which the subject has already developed some disability requiring pharmacological treatment, and a second stage in which the subject develops motor complications associated with levodopa usage. The treatment for the first stage aims to provide proper symptom control while minimizing the side effects of dopamineric function improvement. The need for levodopa (or L-DOPA) treatment can be delayed by using other medications such as dopamine agonists ad MAO-B inhibitors, which could in turn delay the onset of dyskinesias. The treatment for the second phase of Parkinson’s disease, meanwhile, aims to reduce symptoms while reducing fluctuations of the patient’s response to medication. Overuse or sudden withdrawals from medication must be carefully monitored and managed. Patients in the final stage of the disease receive palliative care to improve quality of life.
Surgery, meanwhile, used to be a common practice for treating the motor symptoms of PD, but the discovery of levodopa lead to a significant decrease in operations. On the other hand, surgery is still used in people with advanced PD for whom drug therapy no longer works well enough. Surgery for Parkinson’s disease can be classified into two main categories: lesional and deep brain stimulation (DBS). Target areas for deep brain stimulation include the thalamus, the globulus pallidus or the subthalamic nucleus. DBS is typically recommended for PD patients who experience motor fluctuations and tremor for which medication is no longer sufficient. Less common surgeries involve intentional formation of lesions in order to suppress an over-activity of specific subcortical areas. Pallidotomy, for instance, entails the destruction of the globules pallidus through surgery to control diskinesia.
Outlook for Parkinson’s Disease Patients
Parkinson’s disease invariably progresses as time goes by. The Hoehn and Yahr scale is often used to estimate the progress of the disease, defining five stages of progression. If left untreated, motor symptoms of PD can advance aggressively in the initial stages of the disease and more slowly later. Without proper treatment, subjects are expected to lose independent ambulation after an average of eight years and become bedridden in ten years.
Proper medication, however, has provided notable improvements in the prognosis of motor symptoms. On the other hand, medication is at the same time a new source of disability, as levodopa can have significant side effects after years of use. Patients on levodopa may extend the progression time of symptoms to over 15 years before reaching a stage of high dependency on care givers. The disease can also be hard to predict at times, as it doesn’t take the same course for all individuals. Age remains the best predictor of disease progression. One other hint is that the rate of motor decline appears to be greater in patients with less impairment at the time of diagnosis, while subjects over age 70 at symptom onset are more commonly experiencing cognitive impairment.
After ten years with PD, most patients experience autonomic disturbances, mood alterations, sleep problems, and cognitive decline. All of these symptoms, particularly cognitive decline, considerably increase disability.
The life expectancy of people with Parkinson’s disease is reduced, with mortality ratios roughly twice those of the general population. Mmortality risk factors include old age at onset, cognitive decline and dementia, a more advanced disease state, and the presence of swallowing problems. Death from aspiration pneumonia is also twice as common in individuals with PD compared to unaffected individuals. A disease pattern mainly displaying tremor instead of rigidity predicts an improved life expectancy.
Parkinson’s disease is the second-most common neurodegenerative disorder after Alzheimer’s disease. PD is more common in the elderly, with the main age of onset at around 60 years.