Intro
Parkinson’s disease is a progressive neurological condition that affects movement, and increasingly recognised for its impact on sleep, mood, cognition, and autonomic function. It is the second most common neurodegenerative condition after Alzheimer’s disease, affecting approximately 10 million people worldwide.
Parkinson’s is caused by the gradual loss of dopamine-producing neurons in a brain region called the substantia nigra. The condition is manageable — not curable — but with modern treatment, exercise, and multidisciplinary care, most people with Parkinson’s live for many years with maintained quality of life.
Key Points
- Parkinson’s disease is a progressive movement disorder caused by dopaminergic neuron loss
- Classical motor features: resting tremor, bradykinesia (slowness of movement), and rigidity
- Non-motor features — sleep problems, constipation, depression, autonomic dysfunction — often precede motor symptoms
- Asymmetric onset (one side of the body first) is characteristic
- Levodopa remains the most effective motor treatment; other medications, DBS surgery, and physiotherapy are also used
- Exercise is strongly evidence-supported and should be started early and maintained
- Prognosis is variable; many people live well for many years with appropriate care
Background: Dopamine and the Substantia Nigra
Movement control requires precise signalling in the brain’s basal ganglia circuits. The substantia nigra — a small region in the midbrain — produces dopamine that coordinates smooth, controlled movement.
In Parkinson’s disease, neurons in the substantia nigra progressively die. By the time motor symptoms appear, an estimated 60–80% of dopaminergic neurons in that region have already been lost. This is why early diagnosis can be challenging — the brain compensates for a time before motor signs become apparent.
The hallmark pathological finding is Lewy bodies — abnormal protein aggregates (primarily alpha-synuclein) that accumulate in surviving neurons and spread through the nervous system. Lewy body pathology extends beyond the substantia nigra, which explains the broad range of non-motor features in Parkinson’s.
Motor Symptoms
The three cardinal features of Parkinson’s disease:
1. Tremor (resting tremor)
- Occurs at rest — when the limb is relaxed and still
- Typically improves when the hand moves (unlike essential tremor, which occurs with action)
- Often described as a “pill-rolling” motion of the thumb and fingers
- Usually begins on one side; may involve the hand, arm, leg, jaw, or lip
- Tremor is the most visible symptom but is not the most disabling
2. Bradykinesia (slowness of movement)
- The most functionally limiting feature
- Manifests as slowness in starting movements, small shuffling steps, reduced arm swing when walking
- Writing becomes small and cramped (micrographia)
- Facial expression may reduce (hypomimia or “masked facies”)
- Voice may become softer (hypophonia)
3. Rigidity
- Muscle stiffness, often with a “cogwheel” quality detected by a doctor during examination
- Can cause aching muscles, shoulder pain (sometimes misdiagnosed initially as shoulder disease), and reduced range of motion
Other motor features
- Postural instability — impaired balance and righting reflexes, increasing fall risk in later disease
- Freezing of gait — sudden, temporary inability to initiate steps; can occur in doorways or crowded spaces
- Stooped posture
Non-Motor Symptoms
Non-motor features are common, often precede the motor diagnosis by years, and significantly affect quality of life:
Sleep disturbances
- REM sleep behaviour disorder (RBD): acting out vivid dreams during sleep — thrashing, shouting, kicking. This can precede Parkinson’s by a decade or more and is considered a prodromal marker
- Excessive daytime sleepiness
- Restless legs syndrome
- Sleep fragmentation and insomnia
See Sleep and Health for context on sleep health.
Autonomic symptoms
- Constipation — often appears years before motor diagnosis
- Orthostatic hypotension — blood pressure drop on standing, causing dizziness or falls
- Urinary urgency or frequency
- Sweating abnormalities
- Sexual dysfunction
Neuropsychiatric symptoms
- Depression and anxiety — extremely common; often undertreated
- Cognitive slowing — many people experience mild slowing of processing and multitasking
- Parkinson’s disease dementia — affects a subset of people, usually in later disease stages
- Psychosis — visual hallucinations can occur, often medication-related
Sensory symptoms
- Loss of sense of smell (anosmia) — common prodromal feature
- Pain — musculoskeletal and neuropathic pain are common
Diagnosis
There is no definitive blood test or scan that diagnoses Parkinson’s. Diagnosis is clinical — based on history, neurological examination, and response to treatment.
Clinical criteria (MDS)
The Movement Disorder Society criteria require:
- Bradykinesia as a core feature
- Plus at least one of: resting tremor, rigidity
- Absence of features suggesting an alternative diagnosis (atypical parkinsonism)
Supportive features
- Clear and sustained response to levodopa
- Asymmetric onset
- Resting tremor
Investigations to exclude other causes
- Brain MRI — to exclude stroke, normal pressure hydrocephalus, or structural causes
- Blood tests — thyroid function, calcium, ceruloplasmin (Wilson’s disease in younger patients)
- DAT-SPECT scan (DaTscan) — measures dopamine transporter activity in the brain; useful when diagnosis is uncertain
Distinguishing Parkinson’s from similar conditions
Several conditions mimic Parkinson’s (atypical parkinsonism) and have different prognoses and responses to treatment:
- Progressive Supranuclear Palsy (PSP): prominent falls, gaze palsy
- Multiple System Atrophy (MSA): early autonomic failure, cerebellar features
- Corticobasal Syndrome (CBS): marked asymmetry, “alien limb” phenomenon
Treatment
Treatment is aimed at managing symptoms and maintaining function. There is no disease-modifying treatment that halts progression, though exercise and neuroprotective strategies are under active research.
Levodopa (L-DOPA)
Levodopa — usually combined with carbidopa or benserazide to prevent peripheral breakdown — is the most effective motor treatment. It crosses the blood-brain barrier and converts to dopamine.
Benefits:
- Substantially reduces bradykinesia, rigidity, and tremor
- Improves gait and daily function dramatically in most patients
Long-term considerations:
- After several years, many patients experience motor fluctuations — “wearing off” of the medication before the next dose
- Dyskinesias (involuntary writhing movements) can develop, related to cumulative levodopa exposure and pulsatile dopamine receptor stimulation
- These complications are managed with dose adjustments, additional medications, or DBS
Dopamine agonists
Act directly on dopamine receptors; used as initial therapy (especially in younger patients to delay levodopa) or as add-on therapy.
Examples: pramipexole, ropinirole, rotigotine (patch)
Side effects include impulse control disorders (gambling, hypersexuality) — patients and families should be aware of this risk.
MAO-B inhibitors
Selegiline, rasagiline, safinamide — reduce dopamine breakdown in the brain; used alone early in disease or as add-on to levodopa.
COMT inhibitors
Entacapone, opicapone — extend levodopa effect; useful for “wearing off”
Advanced therapies
- Deep Brain Stimulation (DBS): surgical implantation of electrodes in specific brain regions (subthalamic nucleus or globus pallidus); highly effective for motor fluctuations, dyskinesias, and tremor in carefully selected patients
- Levodopa-carbidopa intestinal gel (LCIG): continuous infusion via jejunal tube; for severe motor fluctuations not managed with oral medications
- Focused ultrasound thalamotomy: non-invasive procedure for tremor-predominant disease
Exercise and Physical Therapy
Exercise is the most robust non-pharmacological intervention in Parkinson’s disease.
Evidence-based benefits
- Reduces motor symptom severity
- Improves balance and gait
- Reduces fall risk
- Improves mood and quality of life
- May slow disease progression via neurotrophic pathway activation (BDNF, neuroplasticity)
What the evidence supports
- Aerobic exercise: cycling (particularly forced cycling at high cadence), walking, swimming
- Resistance training: maintains muscle strength and slows sarcopenia
- Boxing-style programmes (e.g., Rock Steady Boxing): improve speed, coordination, balance
- Dance (especially tango): improves balance, gait, and social engagement
- Tai Chi: strong evidence for fall prevention
Exercise should begin early and be maintained as a lifelong priority.
Physiotherapy and occupational therapy
- Physiotherapy targets gait, balance, and transfers
- LSVT BIG — an intensive exercise programme specifically designed for Parkinson’s; improves motor amplitude
- Occupational therapy helps maintain independence in daily activities
Speech and Swallowing
- Hypophonia (soft voice) and dysarthria (unclear speech) affect many people
- LSVT LOUD — an intensive speech therapy programme that significantly improves voice volume
- Swallowing difficulties (dysphagia) can develop in later stages and increase aspiration risk — a speech pathologist should assess and advise
Cognitive Changes and Dementia
Mild cognitive changes — particularly in executive function (planning, multitasking), attention, and processing speed — are common in Parkinson’s and do not indicate dementia.
Parkinson’s disease dementia (PDD) — affecting memory, orientation, and daily function — develops in approximately 80% of patients who survive long enough, typically in later disease stages. Lewy body pathology extending to the cortex is the underlying cause.
Dementia with Lewy Bodies (DLB) is a closely related condition where dementia and parkinsonism occur simultaneously or dementia precedes motor symptoms.
See Dementia Overview and Cognitive Testing and Memory Assessment for further information.
Living Well with Parkinson’s Disease
- Exercise consistently — the single most important self-management behaviour
- Sleep hygiene — treat RBD and sleep problems; good sleep protects cognition and mood
- Nutrition — adequate protein is important (though very high protein intake can interfere with levodopa absorption; timing of protein relative to medication may be relevant)
- Psychological support — depression and anxiety are treatable and should not be accepted as inevitable
- Care planning — involving family, allied health, and a specialist movement disorder neurologist
- Parkinson’s organisations — Parkinson’s Australia, Parkinson’s UK, Parkinson’s Foundation provide resources, local support groups, and advocacy
Further Reading
- Parkinson’s Foundation
- Parkinson’s UK
- Michael J. Fox Foundation
- EAU/MDS Guidelines on Parkinson’s Disease