Parkinson’s Disease

Parkinson’s disease is a neurologic disorder of old age, usually affecting more than 60 years of age. It is characterized by slowly developing disabilities due to the loss of dopamine in the brain cells. Parkinson’s disease is incurable, and currently, there is no treatment available that can cure the condition; only the disease progression can be slowed down.

According to an estimate, more than 10 million people live with Parkinson’s disease in the world each year. About 1 million of these live in the United States. Almost 60 thousand people are diagnosed with Parkinson’s disease each year in the United States alone.

Parkinson’s disease is caused by the loss of dopaminergic neurons in a particular brain area called substantia nigra. The exact mechanism by which destruction occurs is unknown, but various genetic and environmental factors are believed to be responsible for it.

Parkinson’s disease occurs worldwide, but the prevalence varies. It is predominantly a disease of old age, and symptoms appear at around 60 years of age. In very rare cases, signs and symptoms might appear as early as 40 years of age. It is more common in men than in women.

According to various studies, the environmental risk factors for Parkinson’s disease include:

• Exposure to pesticides
• Living in rural areas
• Consumption of well water
• Exposure to industrial plants

Genetic factors are responsible for about 10% of all disease cases. In cases involving genetics, the disease onset is seen in the early years, around 50 years of age. People with type 2 diabetes are at a 30% increased risk of developing Parkinson’s disease.

Following are the signs and symptoms of Parkinson’s disease:

• Characteristic motor symptoms include tremors upon resting, rigidity, weakness, slowness of movements, gait difficulty, postural imbalance. 
• Decrease in cognitive function of the brain
• Memory loss
• Decrease in dexterity
• Soft voice
• Loss of facial expressions
• Decreased range of motion of shoulder joint of the affected side
• Sleep disturbances
• Decrease sense of smell
• Autonomic dysfunction that manifests itself as constipation, sweating, sexual disturbances, and dermatitis
• Anhedonia- loss of feeling of pleasure or happiness
• Generalized weakness

Diagnosis of Parkinson’s disease is based upon clinical signs solely. The presence of characteristic motor signs is sufficient for the diagnosis. If two of the three characteristic motor symptoms are present in any patient, the diagnosis can be confirmed. These include:

• Tremors (uncontrolled, rhythmic movements of the body, usually of limbs)
• Rigidity (abnormal stiffness of muscles)
• Bradykinesia (slowness of movements)

Although lab tests and radiological tests are of no significant importance, brain scans using MRI or CT can be done to rule out other neurological causes such as space-occupying lesions, hydrocephalus, and other disorders.

Differential diagnoses of Parkinson’s disease include:

• Multiple system atrophy (MSA)
• Progressive supranuclear palsy (PSP)
• Drug-induced Parkinsonism
• Vascular Parkinsonism
• Alzheimer’s disease
• Cardioembolic stroke
• Chorea
• Huntington disease
• Lacunar syndrome
• Hydrocephalus
• Essential tremor
• Parkinson plus syndromes

There is no specific cure for the disease, yet the treatment aims to slow down the progression. Following treatment regimen are usually prescribed:

• Dopamine replacement in the form of dopaminergic drugs is done to control motor symptoms caused by the loss of dopamine. These drugs include levodopa and carbidopa. They are standard drugs for treatment.
• Other dopamine agonists, such as ropinirole, etc., can also be used.
• For non-motor symptoms due to dopamine loss, monoamine oxidase inhibitors (MAO inhibitors) can be used.
• Autonomic symptoms such as tremors can be controlled with anticholinergic drugs. Specific drugs are used for non-motor symptoms such as erectile dysfunction and excessive somnolence.
• Exercise and physical therapy are said to improve the motor functions such as postural imbalance and gait disturbances in patients.
• Due to laryngeal involvement, there are speech disturbances in patients that can affect their ability to communicate effectively. Speech therapy is designed for such patients to improve their communication and consciously improve facial expressions.
• Surgical interventions can also include deep brain stimulation to improve responsiveness to levodopa therapy, neuro-ablative lesion surgeries, neural transplantation, etc.
• Dietary modifications include avoiding meals with high protein content as it can affect the absorption of levodopa.

Before discovering levodopa, Parkinson’s disease was associated with considerable disability and death rate. After its introduction, the death rate decreased to half, and longevity was increased to many years. The factors that predict the prognosis of Parkinson’s include:

• Old age-onset with tremors as the first symptoms compared to motor rigidity or bradykinesia have comparatively a good prognosis
• If the patient is male and has comorbidities as well, the disease progresses rapidly
• Old age-onset with dementia and non-responsiveness to dopamine therapy has a poor prognosis

• Patient and caregiver education is essential for proper support and care. Disease management becomes difficult with disabilities and major personality changes with symptoms such as memory loss, cognitive decline, motor decline, irritability, fatigue, depression, etc.
• According to one study, vigorous exercise in middle life is thought to provide some sort of neuroprotective effect in the brain against Parkinsonism. It produces a neurotrophic factor in the brain and in serum that can prevent harmful toxins that potentially cause Parkinson’s disease to affect the brain.
• Eat more green vegetables and incorporate vitamin E and coenzymes in your diet, as they are thought to have neuroprotective benefits.
• Patients with Parkinson’s disease have eating difficulties. Due to laryngeal involvement, they are at an increased risk of inhaling food or saliva into the lungs that can cause aspiration pneumonia. More than 70% of deaths in people with Parkinson’s are caused by aspiration pneumonia, so special care should be taken in such patients while eating food.

Our clinical experts continually monitor the health and medical content posted on CURA4U, and we update our blogs and articles when new information becomes available. Last reviewed by Dr.Saad Zia on May 08, 2023.

References

https://www.nia.nih.gov/health/parkinsons-disease#:~:text=Parkinson's%20disease%20is%20a%20brain,have%20difficulty%20walking%20and%20talking.

https://www.sciencedirect.com/science/article/abs/pii/S014067362100218X