What are the clinical manifestations of Parkinson's Disease?

Clinical Manifestations of Parkinson's Disease

Parkinson's disease (PD) is characterized by both motor and non-motor symptoms, with the cardinal motor features being resting tremor, bradykinesia, rigidity, and postural instability, resulting from progressive degeneration of dopaminergic neurons in the substantia nigra. 1, 2

Cardinal Motor Symptoms

1. Bradykinesia

• Slowness of movement and decreased amplitude of movement
• Progressive reduction in speed and amplitude during repetitive movements
• Difficulty with fine motor tasks (buttoning clothes, handling utensils)
• Decreased facial expression (hypomimia)
• Reduced arm swing while walking

2. Rigidity

• Increased muscle tone throughout the range of passive movement
• Can present as:
  • "Lead-pipe" rigidity (uniform resistance)
  • "Cogwheel" rigidity (ratchet-like resistance when combined with tremor)
• Often asymmetric at disease onset

3. Resting Tremor

• Typically 4-6 Hz frequency
• Present at rest, decreases with voluntary movement
• Usually begins unilaterally, often in the hands ("pill-rolling" tremor)
• May involve lips, chin, jaw, and legs
• Absent during sleep

4. Postural Instability

• Occurs later in disease progression
• Impaired righting reflexes
• Propensity for falls
• Festinating gait (short, shuffling steps with forward-leaning posture)
• Poor balance, especially when turning

Secondary Motor Symptoms

Gait Abnormalities

• Shuffling gait with small steps
• Freezing of gait (sudden inability to move forward)
• Festination (involuntary acceleration of gait)
• Difficulty initiating movement (start hesitation)

Speech and Swallowing Difficulties

• Hypophonia (soft speech)
• Monotonous speech with reduced modulation
• Dysarthria (slurred speech)
• Dysphagia (difficulty swallowing)
• Drooling due to reduced automatic swallowing

Handwriting Changes

• Micrographia (small, cramped handwriting)
• Progressive decrease in letter size across a line of text

Non-Motor Symptoms

Autonomic Dysfunction

• Orthostatic hypotension
• Constipation (often precedes motor symptoms by years)
• Urinary urgency and frequency
• Sexual dysfunction
• Excessive sweating
• Seborrheic dermatitis

Neuropsychiatric Symptoms

• Depression (affects up to 40% of patients)
• Anxiety
• Apathy
• Cognitive impairment progressing to dementia in advanced stages
• Psychosis (hallucinations, delusions) - often medication-related 3, 4
• Impulse control disorders (pathological gambling, hypersexuality, compulsive shopping) - particularly with dopamine agonist therapy 4

Sleep Disorders

• REM sleep behavior disorder (may precede motor symptoms by years)
• Excessive daytime sleepiness 3
• Insomnia
• Restless legs syndrome
• Sleep fragmentation

Sensory Symptoms

• Hyposmia/anosmia (reduced/absent sense of smell) - often an early symptom
• Pain (often in the affected limb)
• Paresthesias
• Visual disturbances

Disease Progression

PD typically follows a progressive course with variable rates of progression between individuals 2:

• Early Stage: Unilateral symptoms, minimal functional disability
• Intermediate Stage: Bilateral involvement, postural abnormalities, moderate disability
• Advanced Stage: Severe disability, freezing, falls, cognitive decline

Clinical Subtypes

Different clinical subtypes have been identified 2:

• Tremor-dominant: Better prognosis, slower progression
• Postural instability and gait difficulty (PIGD): More rapid progression, higher risk of dementia
• Diffuse malignant subtype (9-16% of PD patients): Early prominent motor and non-motor symptoms, poor medication response, faster progression
• Mild motor-predominant (49-53% of PD patients): Mild symptoms, good response to dopaminergic medications, slower progression

Diagnostic Considerations

The diagnosis of PD is primarily clinical, based on the presence of cardinal motor features and response to dopaminergic therapy. It's important to distinguish PD from atypical parkinsonian syndromes like Progressive Supranuclear Palsy (PSP), which presents with early falls, vertical gaze abnormalities, and poor levodopa response 5.

Common Pitfalls in Diagnosis

• Overlooking early non-motor symptoms: Hyposmia, REM sleep behavior disorder, and constipation may precede motor symptoms by years
• Missing medication side effects: Dopaminergic medications can cause hallucinations, impulse control disorders, and sudden sleep onset 3, 4
• Attributing symptoms to normal aging: Slowness and stiffness may be dismissed as age-related changes
• Focusing only on tremor: Not all PD patients have tremor, and not all tremors indicate PD
• Failing to recognize disease progression: Symptoms evolve over time, with increasing disability and emergence of treatment-resistant features

Early recognition of both motor and non-motor manifestations is crucial for timely diagnosis and management to improve quality of life and reduce morbidity in patients with Parkinson's disease.