Overview of Parkinson disease
Parkinsonism is a syndrome diagnosed by bradykinesia plus one of the following features:
- muscular rigidity
- 4 to 6 Hz rest tremor
- postural instability not caused by primary visual, vestibular, cerebellar or proprioceptive dysfunction.
Parkinsonism has many causes, but sporadic idiopathic Parkinson disease is the most common. While clinical criteria help distinguish Parkinson disease from other causes, autopsy studies show that diagnostic accuracy is only around 80%. Features that support a diagnosis of Parkinson disease include unilateral rest tremor, excellent response to levodopa, a progressing disorder and persistent asymmetry. Certain clinical features (see Features that suggest a diagnosis other than Parkinson disease) should prompt a review of the diagnosis. If the diagnosis is in doubt, refer for expert advice.
early dementia
early falls
early severe autonomic dysfunction
other neurological signs (eg upper motor neurone signs, abnormal eye movements, cerebellar signs)
onset of symptoms coinciding with dopamine antagonist treatment (eg antipsychotic drugs, metoclopramide)
no response to large doses of levodopa (if malabsorption is excluded)
history of repeated strokes with stepwise progression of parkinsonian features
Nonmotor complications of Parkinson disease are major causes of disability, even in the early stages of the disease. These complications include fatigue, neuropsychiatric symptoms (eg depression, anxiety, psychosis), sleep disturbance, autonomic symptoms (eg orthostatic hypotension, bladder dysfunction, constipation, sexual dysfunction), pain and other sensory symptoms, and dysphagia. Dementia is common in late disease, with a prevalence of 20 to 40%. See advice on orthostatic hypotension, neuropsychiatric symptoms, bladder dysfunction, dementia and sialorrhoea.
Many genes associated with Parkinson disease have been identified, but genetic mutations account for only 1 to 2% of sporadic cases. No therapy directed at specific gene mutations is available at the time of writing.
Parkinson disease has no cure, so the principles of treatment are to:
- keep the patient functioning as long as possible with the minimum amount of medication
- choose each patient's therapy according to their disease stage and main symptoms.
Levodopa and dopamine agonists are the main drugs used to improve motor function in Parkinson disease. Parkinson disease does not need pharmacotherapy when it does not cause functional impairment. Deciding when to start therapy and the type of therapy varies for each patient, based on a range of factors (eg age, occupation, activity level, economic status, patient preference, cognitive state).
As Parkinson disease progresses, most patients need levodopa. A consistent response to levodopa is diminished with prolonged use, leading to motor complications. Nonmotor complications also become worse in advancing Parkinson disease. Autonomic dysfunction is not usually as severe as in multiple system atrophy (one of the differential diagnoses of Parkinson disease).
When the disease progresses, discuss advance care planning with the patient. Some patients will need palliative care.
Nonpharmacological intervention is essential at all stages of Parkinson disease, and many disciplines (eg physiotherapy, speech therapy, occupational therapy, dietetics) are involved. Studies suggest that various physical therapies (including active music therapy, treadmill training, balance training and ‘cued’ exercise training [using visual and auditory cues to treat freezing]) can improve function in patients with Parkinson disease. Although the functional improvement is small and not sustained, physical therapy actively involves patients in their disease.