Parkinson's Disease for USMLE Step 2 / COMLEX-USA Level 2
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Clinical Presentation
- Motor Symptoms:
- Bradykinesia: Significant slowness of movement, difficulty initiating movements.
- Rigidity: Stiffness in muscles throughout the body.
- Resting Tremor: Noticeable shaking, typically a "pill-rolling" tremor of the hands at rest.
- Postural Instability: Poor balance and coordination, risk of falls.
- Non-Motor Symptoms:
- Cognitive Decline: Ranging from mild impairment to dementia in advanced stages.
- Mood Disorders: Depression and anxiety are common.
- Autonomic Dysfunction: Issues like constipation, urinary urgency, orthostatic hypotension.
- Sleep Disturbances: Especially REM sleep behavior disorder.
Diagnostic Approach
- Clinical Diagnosis: Based on motor symptoms and response to dopaminergic therapy.
- Supportive Tests:
- DaTscan: Helps differentiate PD from other types of parkinsonism by assessing dopamine transporter levels in the brain.
- MRI: Used to rule out other causes of symptoms but not diagnostic for PD.
Management
- Pharmacological Treatment:
- Levodopa/Carbidopa: Most effective for symptomatic control, monitored for dose adjustments based on response and side effects.
- Dopamine Agonists: Pramipexole, ropinirole—used in younger patients or early disease.
- MAO-B Inhibitors: Selegiline, rasagiline—used either alone in early disease or as adjunct therapy.
- COMT Inhibitors: Entacapone, tolcapone—enhance effects of Levodopa.
- Non-Pharmacological:
- Physical Therapy: Focus on mobility, strength, and balance.
- Occupational Therapy: Help with daily activities and adaptive techniques.
- Speech Therapy: For speech and swallowing issues.
Complications and Monitoring
- Motor Fluctuations and Dyskinesias: Due to long-term Levodopa use.
- Psychiatric Complications: Particularly hallucinations and psychosis, especially in the elderly or those on higher doses of medication.
- Neurological Consultation: For complex cases or when diagnosis is uncertain.
High-Yield Items for Step 2
1. Diagnosis of PD: Emphasis on clinical presentation and response to Levodopa.
2. Management Strategies: Detailed knowledge of pharmacological agents used in PD, including their side effects and indications.
3. Differential Diagnosis:
- Essential Tremor: Distinguished by action tremor and lack of other parkinsonian features.
- Drug-Induced Parkinsonism: Caused by dopamine receptor blockers.
- Atypical Parkinsonisms: Like PSP or MSA, which have additional clinical features and poor response to Levodopa.