Parkinson's Disease

Parkinson's disease (PD) is a long-term neurodegenerative disorder affecting the central nervous system, primarily impacting motor function. It is characterised by a gradual onset of symptoms that worsen over time.

The primary motor symptoms include tremor, bradykinesia (slowness of movement), rigidity, and postural instability. These are collectively known as parkinsonism.

Non-motor symptoms such as dysautonomia, depression, anxiety, and sleep disorders also commonly occur, especially in later stages of the disease.

Signs and Symptoms

Motor symptoms are the hallmark of PD and include:

• Tremor: Often described as a "pill-rolling" motion, typically starting in the hands and can affect other parts of the body.
• Bradykinesia: This includes difficulties in planning, initiating, and executing movement, affecting everyday tasks.
• Rigidity: Increased muscle tone leading to stiffness and resistance to movement.
• Postural Instability: Impaired balance leading to falls, common in the later stages of PD.

Non-motor symptoms may precede motor symptoms and include constipation, loss of smell (anosmia), and REM sleep behaviour disorder. As PD progresses, symptoms such as dementia, psychosis, orthostatic hypotension, excessive sweating, and urinary incontinence can develop.

Causes and Risk Factors

The exact cause of PD is unknown but is believed to result from a combination of genetic and environmental factors. Age is the most significant risk factor, with the prevalence increasing in individuals over 60.

Genetic mutations in genes such as SNCA, LRRK2, and PARK2 are linked to familial forms of PD. Environmental factors include exposure to pesticides and heavy metals, with some protective factors being caffeine and nicotine consumption.

Pathophysiology

PD is characterised by the degeneration of dopamine-producing neurons in the substantia nigra of the brain. This leads to reduced dopamine levels, affecting the basal ganglia, which play a very important role in motor control.

The presence of Lewy bodies, abnormal aggregates of alpha-synuclein protein, is a pathological hallmark of PD.

Diagnosis

Diagnosis is primarily clinical, based on medical history and neurological examination. Key diagnostic criteria include the presence of bradykinesia combined with either tremor or rigidity.

Medical imaging, such as neuromelanin MRI, can support the diagnosis, though it is mainly used to rule out other conditions.

Treatment

There is no cure for PD, and treatment focuses on managing symptoms. Medications such as Levodopa, dopamine agonists, COMT inhibitors, and MAO-B inhibitors are commonly used to increase dopamine levels or mimic its action in the brain.

Deep brain stimulation (DBS) is a surgical option for patients with severe motor symptoms unresponsive to medication. Physical therapy and exercise are essential components of managing PD, improving mobility, flexibility, and quality of life.

Prognosis

PD is a progressive disease with a variable course. While medication can significantly improve quality of life, motor complications and non-motor symptoms increase with disease duration.

Life expectancy is near-normal, though advanced stages of the disease often lead to severe disability and increased risk of complications such as aspiration pneumonia, which is a leading cause of death in PD patients.

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Self-assessment MCQs (single best answer)

What is the most common initial symptom of Parkinson's disease?

Which brain region is primarily affected in Parkinson's disease?

Which of the following is NOT a common motor symptom of Parkinson's disease?

What protein aggregates to form Lewy bodies in Parkinson's disease?

Which medication is commonly the first choice for treating motor symptoms in Parkinson's disease?

What is the primary risk factor for developing Parkinson's disease?

Which of the following is NOT typically used in the diagnosis of Parkinson's disease?

What is the term for the slow movement characteristic of Parkinson's disease?

Which surgical treatment is used for patients with severe motor symptoms unresponsive to medication in Parkinson's disease?

What non-motor symptom is often one of the earliest signs of Parkinson's disease?