Parkinson's Disease: Clinical Features and Diagnosis
Medically Reviewed by Dr. M. Salar Raza | Official SCFHS 2026 Blueprint
Clinical Pathway
Parkinson's disease (PD) is a progressive neurodegenerative disorder caused by the loss of dopaminergic neurons in the substantia nigra. The diagnosis is primarily clinical, based on the presence of cardinal motor features: resting tremor (often described as 'pill-rolling'), bradykinesia (slowness of movement), rigidity (cogwheel rigidity), and postural instability (which tends to occur later in the disease course). A positive response to dopaminergic therapy (like Levodopa) further supports the diagnosis.
Clinical Reasoning
The hallmark of Parkinson's disease is bradykinesia combined with either resting tremor or rigidity. The resting tremor is typically asymmetric at onset and classically decreases with voluntary action, distinguishing it from essential tremor, which is an action tremor. Bradykinesia manifests as difficulty initiating movements, micrographia (small handwriting), and a shuffling gait. Imaging studies like MRI are generally normal in PD and are primarily used to rule out other structural causes of parkinsonism if atypical features are present.
Sample MCQ
A 65-year-old man is brought to the clinic by his wife, who noticed that he has become increasingly slow in his movements and has developed a tremor in his right hand. The tremor is most prominent when his hand is resting in his lap and seems to improve when he reaches for an object. On examination, you note a shuffling gait and decreased facial expression. What is the most likely diagnosis?
- AEssential tremor
- BHuntington's disease
- CParkinson's disease
- DCerebellar ataxia
Correct Answer: Parkinson's disease
The clinical presentation of a resting tremor (improves with action), bradykinesia (slow movements, shuffling gait), and masked facies (decreased facial expression) is highly characteristic of Parkinson's disease. Essential tremor is typically an action or postural tremor, not a resting tremor. Huntington's disease presents with chorea (involuntary, jerky movements) and cognitive decline. Cerebellar ataxia presents with an intention tremor (worsens as the target is approached) and uncoordinated movements.
Master the 2026 SMLE
Explore more clinical protocols in the SMLEREVISE Clinical Knowledge Library.
Try the QBank & Scaled Mocks