Parkinson disease (PD) is a multisystem neurodegenerative disorder that affects about 1% of the population over the age of 55 years and has mean age of onset of about 60 years.

The Braak hypothesis proposes that the earliest pathological evidence of PD is found in the enteric nervous system, medulla and olfactory bulb, and only subsequently progresses (over years) to the substantia nigra and cortex.

Non-motor symptoms, such as constipation, hyposmia and sleep disorders, may precede typical motor features of PD by several years.

No treatment has been convincingly shown to slow PD progression (ie, a neuroprotective drug remains elusive).

Symptomatic benefit from dopaminergic therapy is usually maintained throughout the course of the disease.

The decision as to whether to commence treatment with either levodopa or a dopamine agonist needs to be individually tailored, but long-term outcomes appear to be equivalent.

Advanced PD is complicated by the loss of non-dopaminergic neurones, resulting in symptoms that are largely unresponsive to dopaminergic therapy.

Treatment with apomorphine, Duodopa or deep-brain stimulation surgery may be beneficial for selected patients with advanced PD.

Non-motor symptoms, such as mood disorders, cognitive impairment, autonomic dysfunction and sleep disorders, are responsible for significant morbidity. Management often requires a multidisciplinary approach.