Approach to dementia


Dementia is a syndrome of progressive cognitive impairment which involves multiple cognitive domains and impairs function. It is a clinical diagnosis which may be caused by many different pathological processes, the most common of which is Alzheimer’s Disease.

Mild cognitive impairment is cognitive impairment which does not meet diagnostic criteria for dementia.

DSM-V criteria for diagnosis:

  1. Significant cognitive declines in 1+ of:
    1. Learning and memory
    2. Language
    3. Executive function
    4. Complex attention
    5. Perceptual-motor
    6. Social cognition
  2. Impairing function
  3. Not delirium
  4. Not explained by another diagnosis


Risk factors:

  • Age
  • Low level of education
  • Family history
  • Vascular risk factors


The most common causes of late-onset (>65) dementia are:

  • Alzheimer’s Disease (50%)
  • Vascular
  • Dementia with Lewy Bodies
  • Other

Many patients have mixed pathology, such as a combination of AD and vascular dementia.

Several disease processes can cause dementia. These can be classified in various ways:

  • By age of onset (young vs old)
  • By reversibility (reversible vs irreversible (i.e. neurodegenerative))
  • By speed of onset (acute vs subacute vs chronic)

Differential diagnosis of dementia

  • Neurodegenerative disorders
  • Infection
    • Neurosyphilis
    • Lyme disease
    • AIDS dementia complex
    • CJD
  • Vascular
    • Vascular dementia
  • Nutritional/metabolic
    • B12 deficiency
    • B1 deficiency
    • Hypothyroidism
    • Hyponatraemia
    • Hypercalcaemia
  • Toxic
    • Alcohol
    • Lead poisoning
    • CO poisoning
    • Sedatives
  • Traumatic
    • Post-traumatic (dementia pugilistica)
  • Structural
    • Normal pressure hydrocephalus
    • Space-occupying lesion
      • Chronic subdural haematoma
      • Brain tumour: primary vs metastases


  • Clinical assessment
    • Establish the diagnosis of dementia
      • Impairment in 1+ cognitive domain not accounted for by…
      • Delirium or…
      • Another DSM-V diagnosis, which is leading to…
      • Impairment in ADLs.
    • Establish whether there is an identifiable dementia syndrome / features of a reversible cause
      • Timing
      • Which cognitive domains
      • Other neurological features
      • Systemic features
    • Establish the degree of cognitive impairment: Mini-Mental Status Exam (MMSE)
  • Investigations:
    • Baseline blood tests to exclude reversible causes:
      • FBC
      • U&E
      • Glucose
      • Calcium
      • LFTs
      • TSH
      • ESR
    • Imaging: NICE recommends MRI or CT imaging to exclude structural causes and aid in the differential diagnosis if there is any diagnostic uncertainty.
    • Further tests depend on whether there is clinical suspicion for a particular underlying cause. These are not ‘routine’ but should only be performed if there is diagnostic uncertainty and the results of the investigations will change management.
      • Bloods
        • HIV serology
        • Lyme serology
        • B12
      • CSF
        • Protein 14-3-3 is sensitive for CJD


  • Supportive: most dementia is caused by a neurodegenerative process and so is progressive. The most important aspect to management is therefore ensuring that patients have sufficient care in place to allow them to maintain their independence for as long as possible in a safe environment. People should be advised that they are mandated to inform the DVLA.
  • Treat reversible causes
  • Cognitive enhancers:
    • Cholinesterase inhibitors
    • Memantine
  • Treating associated psychiatric symptoms:
    • Agitation
    • Depression
    • Psychosis