Overview Parkinson’s disease is a progressive neurodegenerative disorder characterised by tremor, rigidity, bradykinesia, and a wide spectrum of non-motor symptoms including sleep disorders, hyposmia, bladder and bowel dysfunction, fatigue, dementia, and other neuropsychiatric symptom. Although the disease has no cure, available treatments effectively control motor symptoms and improve quality of life. Parkinson disease affects approximately 1 percent of persons older than 60 years, and up to 4 percent of those older than 80 years.

Pre-motor features of PD

• Disorders of smell
• Sleep disorders
• Speech disorders
• Autonomic disorders
• Memory changes
• Mood changes
• Sensory changes

4 cardinal motor symptoms (more info below)

• Resting Tremor
• Bradykinesia
• Rigidity
• Postural instability (late finding)

Resting Tremor

• Pill-rolling
• Disappears with voluntary movement and sleep
• 30% no tremor at onset (Most develop as disease progresses)
• asymmetrical

Bradykinesia

• Commonly disabling in the early stages
  • Problems with fine motor tasks: writing, sewing or getting dressed.
  • Decreased blink rate (abnormal glabellar reflex)
• Modified by activity or emotional state
  • Some barely able to walk yet may run if frighten
  • Generally less difficulty when some sort of external cue is provided

Rigidity (Stiff joints)

• Lead-pipe rigidity
• Cogwheel rigidity
• Asymmetrical, neck and shoulder muscles prior to face and extremities.
• With progression, affects the whole body and reduces the ability to move.
• Joint pain is often an initial manifestation of PD

Postural instability

• Late stages with impaired balance/falls
• Diminished arm swing
• Retropulsion, inability to stop
• Gait festination
  • rapid shuffling steps and a forward-flexed posture when walking

Non-motor signs/Autonomic dysfunction

• Can occur years before diagnosis
• Orthostatic hypotension, excessive sweating, urinary incontinence and altered sexual function
• Constipation and gastric dysmotility
• Double vision
• Impaired smell, paresthesias

Tremor, often combined with slowness and stiffness in an arm, presents frequently in general practice. It may be caused by essential tremor, which affects 2-3% of the population. Differentiating essential tremor from Parkinson's disease can be difficult, even for experienced physicians.

Essential tremor (ET)

• ET 10 times more prevalent than Parkinson's Disease.
• ET is a postural ± action tremor. A severe postural tremor may be present at rest but is not ‘pill rolling’.
• Patients with ET may also have: vocal tremor; head tremor (‘no–no’ or ‘yes–yes’).

• Idiopathic Parkinson’s disease (PD)
• Parkinsonian-plus syndromes:
  • Progressive supranuclear palsy
  • Multisystem atrophy (MSA)
  • Corticobasal degeneration (CBD)
• Secondary parkinsonism:
  • Vascular
  • Drug-induced
  • Post-encephalitic
  • Hydrocephalus
• Degenerative disorders:
  • Alzheimer’s disease
  • Parkinson—dementia—MND complex
• Genetic disorders:
  • Wilson’s disease (consider in all cases < 50 years)
  • Huntington’s disease (akinetic rigid (Westphal) variant)
  • Dopa-responsive dystonia

Investigations

• No diagnostic test for Parkinson's Disease. Diagnosis is made on clinical grounds.
• Brain imaging is recommended to rule out vascular disease and hydrocephalus.
• A dopamine transporter scan (DaTscan) - can be used as a confirmatory test.
  • The test cannot distinguish between Parkinson disease and Parkinson-plus conditions.
• Exclude Wilson’s if onset < 50 years:
  • serum copper, caeruloplasmin;
  • 24 hour urinary copper;
  • slit lamp examination for Kayser–Fleischer rings.
• MRI Brain/ CT Brain

Clinical Diagnosis

• Cardinal Signs
  • Distal resting tremor
  • Rigidity
  • Bradykinesia
  • Postural instability
• Patients must also respond to an adequate therapeutic challenge of levodopa or a dopamine agonist
• Symmetrical onset

These features are unilateral at onset, but become bilateral as the condition progresses. Later, postural instability and falls, orthostatic hypotension, decreased olfaction, micrographia and dementia (Lewy bode dementia)

Hallmarks of PD are the presence of Lewy bodies + neuronal cell death in the pars compacta of the substantia nigra.

PD does not develop until striatal dopamine (DA) levels drop to 20% and substantia nigra (SN) cell loss exceeds 50%.

Flow Diagram of the Pathophysiology of Parkinsons

Complications 

• Depression (50%)
• Psychosis (50%)
• Dementia
• Sleep Disturbance
• Excess salivation due to an inabilty to swallow
• Falls and postural instability
• Freezing
• Medication complications
  • Neuroleptic malignant syndrome (when dopamine is stopped suddenly)
  • Serotonin syndrome (cause by MOAI)

Prognosis

• Progressive decline in motor and cognitive function and increased mortality.
  • Risk factors for more rapid decline in motor function include older age at diagnosis, and prominent bradykinesia and rigidity at diagnosis.
  • Prominent tremor at diagnosis may predict a slower rate of disease progression
• Sixty percent of patients with Parkinson disease develop dementia within 12 years of diagnosis.

Overview Essential tremor is an important differential from a pill rolling parkinson tremor. Postural or kinetic tremor in the frequency range of 4 to 12 Hz (usually at the lower end of the range in older patients) is generally the only manifestation in patients with essential tremor. Occasionally, when severe, rest tremor and mild abnormalities of tone and gait may also occur. A family history of this disease and temporary benefit after drinking alcohol are common, but not invariable.

Management

• Mild - no treatment
• Moderate - Severe
  • +/- Propranolol or Primidone