Parkinson's disease

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Parkinson's disease is a progressive neurodegenerative condition of unknown aetiology (idiopathic) (1,2).

It is the second most common neurodegenerative disorder after Alzheimer's disease (3).

The disease results from the degeneration of dopaminergic neurones in the substantia nigra. Clinically the disease becomes evident when approximately 80% of the dopaminergic neurons are lost (2).

Patients with Parkinson's disease classically present with the symptoms and signs associated with parkinsonism (1) :

  • hypokinesia ( poverty of movement)
  • bradykinesia (slowness of movement)
  • rigidity
  • rest tremor

Parkinson's disease should be suspected in those presenting with tremor, stiffness, slowness, balance problems and/or gait disorders (1)

Parkinson's disease is a progressive neurodegenerative condition resulting from the death of dopamine-containing cells of the substantia nigra in the brain. There is no consistently reliable test that can distinguish Parkinson's disease from other conditions that have a similar clinical presentation. The diagnosis is primarily based on a clinical history and examination (1).

Parkinson's disease can be seen in over 120,000 people in UK (2) and affects around 1% of people over the age of 55.

Symptoms usually start between 60-70 years old, but one in 20 of all newly diagnosed disease can be seen in patients younger than 40 years (young-onset Parkinson's disease) (2).

The most common cause of Parkinsonism is Parkinson's disease and it is important for GP's to be able to differentiate between other forms of Parkinsonism and Parkinson's disease (4).

Parkinson's disease is due to the degeneration of dopaminergic neurones in the substantia nigra.

Parkinson's disease has historically been recognised as a primary movement disorder; however, other symptoms may be prominent, such as depression, cognitive impairment and dementia. In the later stages of the disease, people may develop pain and autonomic disturbances (such as dizziness and fainting, and problems with sweating, heart rate, digestion, vision and sexual function)

  • these other symptoms are sometimes described as the 'non-motor' manifestations of Parkinson's disease

Review of diagnosis

  • review the diagnosis of Parkinson's disease regularly, and reconsider it if atypical clinical features develop. (People diagnosed with Parkinson's disease should be seen at regular intervals of 6-12 months to review their diagnosis.) (1)

The condition may progress to cause significant impairments, adversely affecting quality of life and, indirectly, the quality of life of family and carers.

With respect to dopaminergic therapy for motor symptoms of early Parkinson's disease, US guidance states (5):

  • in patients with early PD (Parkinson's disease) who seek treatment for motor symptoms, clinicians should recommend levodopa as the initial preferential dopaminergic therapy
  • clinicians may prescribe DAs (dopamine agonists) as the initial dopaminergic therapy to improve motor symptoms in select early PD patients <60 years who are at higher risk for the development of dyskinesia
  • clinicians should not prescribe DAs to patients with early-stage PD at higher risk of medication-related adverse effects, including individuals >70 years, patients with a history of ICDs, and patients with preexisting cognitive impairment, excessive daytime sleepiness (EDS), or hallucinations
  • clinicians should initially prescribe IR (immediate-release) levodopa rather than CR (controlled-release) levodopa or levodopa/carbidopa/entacapone in patients with early PD
  • in patients with early PD, clinicians should prescribe the lowest effective dose of levodopa (i.e., the lowest dose that provides adequate symptomatic benefit) to minimize the risk of dyskinesia and other adverse effects
  • clinicians should routinely monitor patients taking levodopa for their motor response to treatment and for the presence of dyskinesia, motor fluctuations, ICDs (impulse control disorder), EDS (excessive daytime sleepiness), postural hypotension, nausea, and hallucinations, to guide dosage titration over time
  • clinicians should counsel patients with early PD on the greater motor benefits of initial therapy with levodopa compared with MAO-B (monoamine oxidase type B) inhibitors to inform treatment decisions
  • clinicians may prescribe MAO-B inhibitors as the initial dopaminergic therapy for mild motor symptoms in patients with early PD

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Last edited 11/2021 and last reviewed 05/2022

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