What are the signs of Parkinson's disease upon physical exam?

Physical Examination Signs of Parkinson's Disease

The cardinal physical examination signs of Parkinson's disease include resting tremor (4-6 Hz), rigidity, bradykinesia, and postural instability, with the first three being the most reliable diagnostic features. 1

Cardinal Motor Signs

1. Resting Tremor

• Occurs at rest at a frequency of 4-6 Hz
• Typically begins unilaterally, often in one hand
• Classic "pill-rolling" movement of the thumb against fingers is highly characteristic of PD 2
• Diminishes with voluntary movement and disappears during sleep
• Present in approximately 50% of patients in early stages, with about 15% never developing tremor 2

2. Rigidity

• Increased muscle tone felt as resistance throughout the range of passive movement
• Can be:
  • "Lead-pipe" rigidity (uniform resistance throughout movement)
  • "Cogwheel" rigidity (ratchet-like jerky resistance, especially when combined with tremor)
• Affects both flexor and extensor muscle groups
• Responds to dopaminergic medications (important diagnostic feature) 2

3. Bradykinesia

• Slowness of movement initiation and execution
• Progressive reduction in speed and amplitude of repetitive movements
• Manifests as:
  • Difficulty with fine motor tasks
  • Micrographia (small handwriting)
  • Hypomimia (reduced facial expression)
  • Reduced arm swing while walking
  • Slow, shuffling gait with small steps

4. Postural Instability

• Loss of postural reflexes
• Typically occurs later in disease progression
• Can be assessed with the pull test (patient unable to recover when pulled backward)
• Associated with increased fall risk

Secondary Motor Signs

• Hypomimia (masked facies) - reduced facial expression
• Dysarthria - soft, monotonous speech
• Dysphagia and sialorrhea (drooling)
• Micrographia - progressively smaller handwriting
• Shuffling gait with reduced arm swing
• Festination - involuntary acceleration when walking
• Freezing - sudden, transient inability to move
• Dystonia - abnormal sustained muscle contractions
• Positive glabellar reflex (inability to suppress blinking when tapped repeatedly on the forehead) 1, 3

Asymmetry and Distribution

• Symptoms typically begin unilaterally and remain asymmetric throughout disease course
• Asymmetry is an important diagnostic feature that helps distinguish PD from atypical parkinsonian syndromes 3
• Tremor and rigidity often most noticeable in distal limbs initially

Examination Techniques

1. Tremor assessment:

   • Observe patient at rest with hands in lap
   • Distract patient with mental tasks (counting backward) to elicit subtle tremor
   • Note if tremor diminishes with voluntary movement

2. Rigidity assessment:

   • Passively move patient's limbs while they relax completely
   • Test wrist, elbow, knee, and ankle joints
   • Ask patient to perform movements with contralateral limb to enhance subtle rigidity

3. Bradykinesia assessment:

   • Finger tapping (thumb to index finger) - note speed, amplitude, and rhythm
   • Hand opening/closing rapidly
   • Pronation/supination of hands
   • Heel tapping while seated

4. Gait and posture assessment:

   • Observe spontaneous walking
   • Note stooped posture, reduced arm swing
   • Test turning (may reveal hesitation or multiple small steps)
   • Pull test for postural stability (stand behind patient, pull backward by shoulders)

Clinical Pitfalls and Caveats

• Absence of rest tremor does not rule out PD (occurs in only ~85% of patients) 2
• Early occurrence of falls, severe postural instability, or symmetric symptoms suggests alternative diagnoses 3
• Presence of dementia or hallucinations early in disease course suggests Lewy body dementia rather than PD 1
• Poor or no response to levodopa suggests diagnoses other than idiopathic PD 3
• Autonomic dysfunction, ophthalmoparesis, ataxia, and other atypical features early in disease course suggest alternative diagnoses like Multiple System Atrophy 1, 4

Remember that the physical examination findings must be interpreted in the context of the patient's history, and definitive diagnosis often requires observation of response to dopaminergic therapy and disease progression over time.