Parkinson disease
Parkinson disease is a slowly progressive neurodegenerative disorder from loss of substantia nigra dopaminergic neurons with alpha-synuclein Lewy body pathology, presenting with asymmetric rest tremor, bradykinesia, rigidity, and gait impairment. Diagnosis is clinical; first-line treatment is levodopa-carbidopa or a dopamine agonist.
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What this article covers
- Overview
Definition: a slowly progressive neurodegenerative disorder from loss of dopamine-producing neurons in the substantia nigra pars compacta, producing parkinsonism (bradykinesia plus tremor, rigidity…
- Epidemiology
Age: the dominant driver; incidence and prevalence rise sharply after age 60, with a sharp rise in global incidence expected over the next 20 years.
- Risk factors
Age: the single strongest risk factor, rising with each decade after 60.
- Pathophysiology
Nigrostriatal degeneration: progressive loss of substantia nigra pars compacta dopaminergic neurons reduces striatal dopaminergic input, producing the cardinal motor features once enough neurons are lost.
- Clinical features
Diagnostic criteria (clinical): bradykinesia plus at least one additional cardinal feature (rest tremor, cogwheel rigidity, or postural/gait impairment), with absence of red flags for an atypical parkinsonian syndrome.
- Differential diagnosis
Parkinsonism (broader syndrome): bradykinesia with tremor, rigidity, or postural instability from any cause; ruled distinct here by finding a specific secondary etiology (drug exposure, vascular…
- Diagnosis
Basis of diagnosis: clinical; bradykinesia plus at least one other cardinal feature (rest tremor, rigidity, or postural/gait impairment) and absence of red flags for atypical parkinsonism; no…
- Management
First step, mild symptoms: no treatment initially in mild, non-bothersome disease, or start a monoamine oxidase type B inhibitor (selegiline or rasagiline) for mild relief and to delay levodopa…
- Complications
Motor fluctuations and dyskinesia: occur in up to half of patients after several years of levodopa therapy, including wearing-off, sudden "off," early-morning "off," and peak-dose choreiform dyskinesia.
- Prognosis
Overall trajectory: slowly progressive over years to decades; early motor symptoms remain levodopa-responsive, but late features (gait freezing, postural instability, dysphagia) become progressively less responsive.
- Prevention
No established primary prevention: rigorous daily exercise is the only measure associated with possible disease-modifying benefit on gait and balance, recommended at every stage.
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