Parkinson’s Disease

Definition/diagnostic criteria Parkinson’s disease (PD) is a progressive neurodegenerative disorder characterised by the loss of dopaminergic neurons in the substantia nigra pars compacta. The diagnosis is clinical with diagnostic criteria as follows:

• Bradykinesia and at least one of muscular rigidity, 4–6 Hz rest tremor and postural instability not caused by visual, vestibular, cerebellar or proprioceptive dysfunction.

Epidemiology In the UK, approximately 1 in 500 individuals is affected by Parkinson’s disease, translating to about 127,000 individuals across the nation. The incidence increases with age, typically manifesting in individuals over 50 years old. However, 1 in 20 is under the age of 40 at the time of diagnosis.

Diagnosis
Clinical features: The cardinal symptoms of PD include:

• Rest tremor, bradykinesia, rigidity and postural instability.
• Other clinical features may encompass a range of non-motor symptoms such as mood disorders, sleep disturbances, autonomic dysfunction, and cognitive impairment.

Investigations: While there are no definitive diagnostic tests for PD, certain investigations may be supportive. Neuroimaging, such as dopamine transporter (DAT) SPECT imaging, can help differentiate PD from other conditions like essential tremor or drug-induced parkinsonism. However, its routine use is not recommended and should be reserved for atypical or uncertain cases.

Treatment Treatment aims to alleviate symptoms, as there is currently no cure for PD. Patients should be referred for specialist assessment before starting any medication.

The mainstay of pharmacological treatment includes:

• Dopaminergic therapies such as levodopa, dopamine agonists (e.g., ropinirole, pramipexole), and MAO-B inhibitors (e.g., selegiline, rasagiline).
• Choice of treatment should be individualised, considering factors like age, symptom severity and potential side-effects.
• Adjunct treatments may include physiotherapy, occupational therapy, and speech and language therapy.
• In advanced stages, options like deep brain stimulation may be considered.
• End-stage Parkinson’s disease may require a palliative approach.

Prognosis Parkinson’s disease is a progressive condition, and while the rate of progression can vary, the life expectancy is moderately reduced compared to the general population. Factors influencing prognosis include the patient’s age at onset, the severity of motor symptoms and the presence and severity of non-motor symptoms. While treatment can effectively manage symptoms for years, complications such as immobility and cognitive decline may occur in advanced stages, significantly impacting quality of life.