Educational draft · awaiting clinical reviewThe full textbook explains uncertainty but does not replace live national or local guidance, specialist advice, or current prescribing information.
Identify parkinsonism clinically, refer suspected Parkinson disease untreated for expert confirmation and detect the temporal, autonomic, ocular, cortical and drug-related clues to alternative diagnoses.
Parkinson disease is a progressive synucleinopathy in which nigrostriatal dopamine loss produces a characteristic motor syndrome, but diagnosis remains clinical. Bradykinesia is not simply moving slowly: repetitive actions lose amplitude or rhythm, initiation becomes effortful and automatic movements such as arm swing, blinking and facial expression diminish. Rigidity is velocity-independent resistance, sometimes enhanced by movement of the opposite limb. A classic rest tremor is asymmetric and reduces during purposeful movement, yet a substantial minority of patients never develop it.
History should reconstruct the sequence rather than count current symptoms. Slow unilateral handwriting, reduced arm swing and dexterity followed by tremor fits idiopathic disease. Falls in the first year, rapid wheelchair dependence, early severe dysphagia, inspiratory stridor, disproportionate urinary retention, cerebellar signs, pyramidal signs, vertical gaze palsy, cortical sensory loss or absence of meaningful levodopa response are diagnostic warning signs. Cognitive impairment may occur in Parkinson disease, but very early dementia with visual hallucinations can indicate dementia with Lewy bodies.
Most Parkinson disease is sporadic, with age-related cellular vulnerability and polygenic influences promoting nigrostriatal degeneration and alpha-synuclein accumulation.
Rare pathogenic variants affect lysosomal, mitochondrial and synaptic biology, particularly in young-onset or strongly familial disease.
Population-level exposures can alter risk, but no single toxin or lifestyle factor establishes the diagnosis in an individual.
Misfolded alpha-synuclein disrupts synapses, protein clearance and cellular energy systems within vulnerable neurons as disease progresses.
Degeneration of substantia-nigra neurons reduces dopamine delivery to striatum and distorts basal-ganglia movement selection over time.
Reduced facilitation of desired movement and excessive inhibitory output produce bradykinesia, rigidity, rest tremor and gait change.
Autonomic, sleep, olfactory, mood and cognitive systems become involved, often before or beyond the core motor syndrome.
Repetitive finger taps become progressively smaller and slower, passive movement reveals rigidity, facial expression and blink rate fall and gait has reduced arm swing with short steps and turning en bloc.
A unilateral pill-rolling rest tremor emerges when walking or distracted and reduces with action, while subtle bradykinesia or rigidity confirms parkinsonism rather than isolated tremor.
Longstanding hyposmia, dream enactment, constipation, depression and autonomic symptoms may predate motor disease, but common prevalence means they only modify probability in context.
Early falls, severe autonomic failure, gaze palsy, cerebellar or pyramidal signs, rapid progression, disproportionate axial rigidity, apraxia or cortical sensory loss demand an alternative diagnosis.
Symptoms begin after an antipsychotic, metoclopramide, prochlorperazine, valproate or another dopamine-interfering medicine, often with bilateral signs and coexisting akathisia or tardive movements.
Sudden onset, clear focal deficits or stepwise lower-body gait decline is not typical idiopathic Parkinson disease and should trigger stroke, vascular, toxic, metabolic or structural investigation.
Dopamine-blocker exposure and often bilateral symptoms support an iatrogenic syndrome, although asymmetry and unmasked degeneration can occur.
Bilateral action tremor without bradykinesia or rigidity favours essential tremor; rest tremor alone does not establish Parkinson disease.
Early falls, gaze palsy, severe autonomic failure, stridor, cerebellar or cortical signs favour PSP, MSA or corticobasal syndrome.
Lower-body gait disorder with cerebrovascular lesions or ventriculomegaly and urinary-cognitive features suggests vascular parkinsonism or hydrocephalus.
Freezing, postural instability and orthostatic hypotension cause fractures, fear, deconditioning and dependence as disease advances over time.
Dementia, hallucinations, depression and impulse-control problems can cause more disability and safeguarding risk than limb signs.
Progressive bulbar and cough dysfunction leads to weight loss, medication difficulty and aspiration pneumonia in advanced disease.
Constipation, urinary dysfunction, syncope, REM sleep behaviour disorder and daytime sleepiness impair safety and quality of life.
Arthritis, depression and frailty can cause global slowness; progressive amplitude or speed reduction during repetitive movement is more neurologically specific.
Absence of rest tremor does not exclude Parkinson disease, while isolated tremor without bradykinesia does not establish parkinsonism.
Presynaptic dopaminergic deficit separates essential tremor from degenerative parkinsonism but cannot reliably name which degenerative syndrome is present.
Marked early asymmetry supports idiopathic disease, whereas symmetrical onset raises medication or vascular causes, though neither pattern is absolute.
Urinary symptoms or falls late in established Parkinson disease mean something different from severe retention or repeated falls in the first year.
Regular reconsideration allows an early Parkinson label to evolve into MSA, PSP, CBS or another explanation as discriminating features emerge.
Diagnosing Parkinson disease from tremor alone without demonstrating bradykinesia or rigidity.
Starting levodopa in primary care before the recommended untreated specialist assessment.
Using a dopamine-transporter scan to claim distinction between Parkinson disease and MSA or PSP.
Missing prochlorperazine, metoclopramide or antipsychotic exposure in a patient with new symmetrical parkinsonism.
Reassuring after a normal routine MRI even though Parkinson diagnosis is clinical and red flags persist.
Keeping the original label unchanged despite early falls, gaze palsy, severe autonomic failure or absent adequate levodopa response.
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A 67-year-old has a six-month history of reduced right arm swing, smaller handwriting and a right-sided rest tremor. Examination shows decrement on right finger tapping and rigidity. What is the most appropriate next step?
National guidance is shown before implementation-dependent detail. Typical adult dose examples remain subject to patient factors, contraindications and the live BNF or specialist protocol. Source check completed 27 Aug 2026; clinical approval remains outstanding.
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This does not mean withholding established time-critical Parkinson medicines from a diagnosed patient; deterioration or swallowing failure needs urgent medicines reconciliation.
Antipsychotic relapse, nausea control and withdrawal risks matter. If antipsychotic therapy remains essential, specialist selection of a lower motor-risk option is required.
Nausea, postural hypotension, hallucinations, sleepiness and later fluctuations can occur; response must be judged after adequate exposure and medicines must not be stopped suddenly.
Generic exercise advice is insufficient when freezing, postural instability, aspiration or unsafe work and driving tasks require individual assessment.