Dementia and Parkinson's Disease

Definition | Aetiology | Pathophysiology | Risk factors | Signs and symptoms | Investigations | Management

Definition

Dementia is a progressive neurodegenerative condition characterised by cognitive decline that interferes with daily functioning. Parkinson’s disease (PD) is a neurodegenerative disorder primarily affecting movement but can also cause cognitive decline (Parkinson’s disease dementia).

Aetiology

• Dementia:
  • Alzheimer’s disease (most common).
  • Vascular dementia.
  • Lewy body dementia.
  • Frontotemporal dementia.
  • Parkinson’s disease dementia.
• Parkinson’s disease:
  • Idiopathic neurodegeneration of dopaminergic neurons in the substantia nigra.
  • Genetic predisposition (e.g., LRRK2, PARK2 mutations).
  • Environmental factors (e.g., pesticides, toxins).

Pathophysiology

• Dementia:
  • Progressive neuronal loss and cortical atrophy.
  • Accumulation of amyloid plaques and tau tangles in Alzheimer’s disease.
  • Vascular insufficiency in vascular dementia.
  • Lewy body accumulation in Lewy body dementia.
• Parkinson’s disease:
  • Degeneration of dopaminergic neurons in the substantia nigra.
  • Formation of Lewy bodies composed of alpha-synuclein.
  • Reduction in dopamine levels leading to motor and cognitive symptoms.

Risk factors

• Ageing (strongest risk factor for both conditions).
• Family history of neurodegenerative disease.
• Cardiovascular risk factors (hypertension, diabetes, smoking).
• Head trauma.
• Exposure to environmental toxins.
• Low physical and cognitive activity.

Signs and symptoms

• Dementia:
  • Memory loss (especially recent events).
  • Difficulty with problem-solving and decision-making.
  • Language impairment.
  • Personality and behavioural changes.
  • Hallucinations (more common in Lewy body dementia).
• Parkinson’s disease:
  • Bradykinesia (slow movement).
  • Resting tremor.
  • Rigidity.
  • Postural instability.
  • Non-motor symptoms: cognitive impairment, depression, autonomic dysfunction.

Investigations

• Clinical assessment: detailed history and cognitive assessment (MMSE, MoCA).
• Blood tests: rule out reversible causes (FBC, U&Es, LFTs, TFTs, B12, folate).
• Brain imaging (MRI/CT): assess structural changes, rule out secondary causes.
• DaTSCAN: used in Parkinson’s disease to assess dopaminergic function.
• Neuropsychological testing: detailed cognitive assessment for dementia subtyping.

Management

1. Non-pharmacological interventions:

• Cognitive stimulation therapy for dementia.
• Physiotherapy and occupational therapy for Parkinson’s disease.
• Carer support and education.
• Falls prevention strategies.

2. Pharmacological treatment:

• Dementia:
  • Acetylcholinesterase inhibitors (donepezil, rivastigmine, galantamine) for Alzheimer’s and Lewy body dementia.
  • Memantine for moderate to severe Alzheimer’s disease.
• Parkinson’s disease:
  • Levodopa/carbidopa for motor symptoms.
  • Dopamine agonists (e.g., ropinirole, pramipexole).
  • MAO-B inhibitors (e.g., selegiline, rasagiline).
  • Anticholinergics for tremor (used with caution due to cognitive effects).

3. Management of complications:

• Treatment of depression and anxiety.
• Management of psychotic symptoms (e.g., quetiapine, clozapine in Parkinson’s disease dementia).
• Advanced care planning.

4. Referral:

• Memory clinic: for dementia diagnosis and management.
• Neurology specialist: for Parkinson’s disease assessment and follow-up.
• Physiotherapist and occupational therapist: for mobility and daily function support.

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