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This is a clinician-written, evidence-based summary aligned to the USMLE Step 2 CK Content Outline. It is intended for medical students preparing for USMLE Step 2 CK. Management reflects current ACC/AHA, USPSTF, and APA guidelines. Always cross-reference with UpToDate, institutional protocols, and clinical judgment.
The Bottom Line
- Bradykinesia is required for diagnosis
- Rest tremor, rigidity, and postural instability support diagnosis
- Carbidopa-levodopa is most effective symptomatic treatment
- Dopamine agonists cause impulse-control disorders and hallucinations
- Early falls or gaze palsy suggests atypical parkinsonism
Overview
Parkinson disease results from dopaminergic neuronal loss in substantia nigra with Lewy body pathology. Nonmotor symptoms such as constipation, hyposmia, REM sleep behavior disorder, depression, and autonomic dysfunction may precede motor signs.
Epidemiology
Prevalence rises with age. Drug-induced parkinsonism from dopamine-blocking drugs is an important reversible mimic.
Clinical Features
Symptoms
Slowness, micrographia, difficulty buttoning
Unilateral pill-rolling rest tremor
Rigidity, stiffness, shuffling gait
Constipation, hyposmia, REM sleep behavior disorder
Early frequent falls or vertical gaze palsy is atypical
Signs
Bradykinesia with decrement
Cogwheel rigidity
Masked facies and hypophonia
Reduced arm swing and en bloc turning
Early severe postural instability is red flag
Investigations
First-line
Clinical diagnosisBradykinesia plus rest tremor or rigidity
Medication reviewAntipsychotics, metoclopramide, prochlorperazine, valproate
Second-line
MRI brainAtypical features or structural mimic concern
DaTscanWhen essential tremor vs degenerative parkinsonism unclear
Cognitive/autonomic assessmentWhen Lewy body dementia or MSA suspected
Specialist
Movement disorder evaluationAtypical or advanced disease
Neuropsychological testingDBS candidacy or dementia concern
1
Initial treatment
- Carbidopa-levodopa for significant symptoms or older patients
- Dopamine agonists in selected younger patients
- MAO-B inhibitors for mild symptoms
- Exercise and PT for function
2
Motor fluctuations
- Increase levodopa frequency or add COMT/MAO-B inhibitor
- Amantadine for dyskinesia
- DBS for medication-responsive refractory fluctuations
- Avoid dopamine-blocking drugs
3
Nonmotor care
- Treat constipation, orthostasis, sleep, depression
- Psychosis: reduce offending meds; consider pimavanserin/quetiapine
- Speech/swallow therapy when needed
- Fall prevention
4
Advanced care
- DBS for selected patients
- Palliative planning and caregiver support
- Avoid typical antipsychotics
- Assess driving and safety
Complications
- Falls: Freezing, orthostasis, postural instability
- Dementia/hallucinations: Advanced disease or medications
- Dyskinesia: Chronic levodopa exposure
- Aspiration: Dysphagia in later disease
USMLE Step 2 CK Exam Tips
- 1Bradykinesia is required
- 2Rest tremor improves with action; essential tremor worsens with action
- 3Most effective treatment = carbidopa-levodopa
- 4Dopamine agonists cause gambling/hypersexuality/sleep attacks
- 5Drug-induced parkinsonism is often symmetric
- 6DLB = hallucinations and cognitive fluctuations
- 7PSP = vertical gaze palsy and early falls
practicetest your knowledge on parkinson diseaseApply what you've learnt with USMLE Step 2 CK-style questions from the iatroX Q-Bank — neurology and beyond.
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