• Defined as a progressive impairment of cognitive functions in the absence of any disturbances of consciousness.
  • Prevalence:
    • Increases with age.
    • 5% in the population older than 65 years; 20-40% in older than 85 years. 


1. Cognitive impairment:

  • Characterized by 4 A’s: amnesia, aphasia, apraxia & agnosia.
  • Amnesia: 
    • Memory impairment.
    • Can be episodic (memory for events) & semantic (memory for facts rules, words, and language) & visuospatial deficits.
  • Aphasia: 
    • Disturbances of language function.
  • Apraxia: 
    • Inability to perform learned motor functions.
    • Eg: Difficulties in functions like buttoning the shirt or combing the hair.
  • Agnosia:
    • Inability to interpret sensory stimulus.
    • Most common disturbance -‘prosopagnosia” – Inability identifying face.

Other cognitive impairments:

  • Disturbances in executive functioning (i.e. planning, organizing, sequencing & abstracting).

2. Behavioral & psychological symptoms:

  • Personality changes, hallucinations & delusions, depression, manic & anxiety symptoms, apathy, agitation, aggression, wandering circadian rhythm disturbances, catastrophic reaction.
    • Catastrophic reaction – Subjective awareness of intellectual deficits in stressful situations results in emotional outbursts in the dementia patient.

3. Focal neurological signs & symptoms:

  • Seen in vascular dementia (multi-infarct dementia) corresponding to the site of vascular insults.


1. Depending on reversibility – Reversible dementia (15% patients) & Irreversible dementia.

Causes of reversible dementia:

  • Neurosurgical conditions (subdural hematoma, normal pressure hydrocephalus, intracranial tumors, intracranial abscess).
  • Infectious causes (meningitis, encephalitis, neurosyphilis, Lyme disease).
  • Metabolic causes (vitamin B12 or folate deficiency, niacin deficiency, hypo and hyperthyroidism, hypo & hyperparathyroidism).
  • Others (drugs and toxins, alcohol abuse, autoimmune encephalitis).

2. Depending on the involvement of the area of the brain:

  • Cortical & Sub-cortical (As to area affected by dementing process first).

Cortical dementias: 

  • Clinical features: 
    • Characterized by early involvement of cortical structures & hence, early appearance of cortical dysfunction.
    • Amnesia, apraxia, aphasia, agnosia & acalculia (impaired mathematical skills) indicating cortical involvement.
  • Conditions associated:
    • Alzheimer’s disease – Prototype of cortical dementia.
    • Creutzfeldt-Jakob disease, Pick’s disease & other frontotemporal dementias.

Subcortical dementia: 

  • Clinical features
    • Early involvement of subcortical structures (basal ganglia, brain stem nuclei & cerebellum).
    • Characterized by an early presentation of motor symptoms (abnormal movements like tics, chorea, dysarthria).
    • Significant disturbances of executive functioning.
    • Prominent behavioral & psychological symptoms (apathy, depression, bradyphrenia (slowness of thinking).
  • Conditions associated: 
    • Parkinson’s disease, Wilson’s disease, Huntington’s disease, multiple sclerosis, progressive supranuclear palsy, normal pressure hydrocephalus.

Other types of dementia:

  • Vascular dementia (multi-infarct dementia), lewy body disease (dementia with lewy body), HIV related Dementia, frontotemporol dementia (FTD) & pseudodementia

1. Vascular dementia (multi-infarct dementia):

  • 2nd most common type of dementia.
  • History of stroke.
  • Causes:
    • The occurrence of multiple cerebral infarctions (due to occlusion of cerebral vessels by arteriosclerotic plaques or thromboemboli) —> progressive deterioration of brain functions —> dementia.
    • Acute exacerbations corresponding to new infarcts —> Stepwise deterioration of symptoms (step-ladder pattern).
  • Treatment: 
    • Management of risk factors & cholinesterase inhibitors.

2. Binswanger’s disease:

  • Also referred to as “subcortical arteriosclerotic encephalopathy”.
  • Characterized by multiple small white matter infarctions —> Result in subcortical dementia symptoms.

3. Lewy Body Disease (Dementia with Lewy Body):

  • Clinical features are similar to Alzheimer’s disease.

4. HIV related dementia:

  • Presence of motor abnormalities or personality changes (apathy, emotional lability, or disinhibition).

5. Head trauma-related dementia:

  • Sequelae of head trauma.
  • Dementia pugilistica (punch drunk syndrome) can develop in boxers after repeated head trauma.

6. Frontotemporal Dementia (FTD):

  • Pick’s disease: 
    • One pathological variant of FTD. 
    • Characterized by the presence of pick’s bodies.
    • Earlier onset (45-65 years).
    • Presents with behavioral symptoms & changes in personality with relative memory preservation.

7. Pseudodementia:

  • Depression in elderly patients mimicking dementia symptoms.

Management for dementia:

  • mini-mental status examination (MMSE):
    • Screening test.
    • Evaluation of cognitive functions.
    • A score of less than 24 (out of a maximum 30) – Suggestive of dementia.


  • Cholinesterase inhibitors – Donepezil, rivastigmine, galantamine & tacrine.
  • NMDA receptor antagonist – Memantine.
  • Symptomatic treatment – For behavioral & psychological symptoms of dementia.
    • Includes antidepressants, antipsychotics & benzodiazepines.

Exam Important

  • Cognitive impairment in dementia is characterized by 4 A’s: amnesia, aphasia, apraxia & agnosia.
  • A catastrophic reaction is subjective awareness of intellectual deficits in stressful situations results in emotional outbursts in dementia patients.
  • Reversible causes of dementia include subdural hematoma, normal pressure hydrocephalus, intracranial tumors, and intracranial abscess.
  • Alzheimer’s disease is the prototype of cortical dementia.
  • Binswanger’s disease is also known as subcortical arteriosclerotic encephalopathy.
  • Pick’s disease is one pathological variant of FTD characterized by earlier onset & presence of pick’s bodies.
  • Depression in elderly patients may mimic symptoms of dementia and hence is known as pseudodementia.
  • The evaluation of cognitive functions in dementia is done using a screening test of a mini-mental status examination (MMSE).
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