Overview
Definition
A progressive neurodegenerative disorder characterized by the loss of dopaminergic neurons in the substantia nigra pars compacta.
Epidemiology
Second most common neurodegenerative disease (after Alzheimer's). Usually diagnosed > 60 years old.
Etiology & Risk Factors
- Idiopathic. Characterized pathologically by the accumulation of misfolded alpha-synuclein protein (Lewy bodies) in neurons.
Clinical Symptoms
- Resting tremor ('pill-rolling', usually asymmetric)
- Bradykinesia (slowness of movement, decrementing amplitude)
- Rigidity ('cogwheel' rigidity)
- Postural instability (late finding)
- Non-motor: Anosmia (loss of smell), REM sleep behavior disorder, constipation, depression
Clinical Approach
Diagnosis
- Clinical diagnosis based on the presence of bradykinesia plus tremor or rigidity
- Striatal dopamine transporter imaging (DaTscan) can differentiate from essential tremor but is rarely needed if classic
Management
- Levodopa/Carbidopa (most effective symptomatic treatment, replaces dopamine)
- Dopamine Agonists (Pramipexole, Ropinirole) - often used first in younger patients
- MAO-B Inhibitors (Selegiline, Rasagiline)
- Deep Brain Stimulation (DBS) for severe, medically refractory motor fluctuations
Complications
- Motor fluctuations and dyskinesias (complication of long-term Levodopa use)
- Parkinson's Disease Dementia (PDD)
- Falls and fractures
- Aspiration pneumonia