Dementia

DEMENTIA


DEMENTIA

Introduction:

  • Defined as a progressive impairment of cognitive functions in absence of any disturbances of consciousness.

Prevalence:

  • Increases with age.
  • 5% in population older than 65 years; 20-40% in older than 85 years. 

Symptoms:

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 identifing 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 situation result in emotional outburst in dementia patient.

3. Focal neurological signs & symptoms:

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

Types:

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 involvement of area of brain:

  • Cortical & Sub-cortical (As to area affetced 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.

Subcortical dementia: 

Clinical features

  • Early involvement of subcortical structures (basal ganglia, brain stem nuclei & cerebellum).
  • Characterized by 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:

  • Occurrence of multiple cerebral infarction (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 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 similar to Alzheimer’s disease.

Pick’s dlsease: 

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

7. Pseudodementia:

  • Depression in elderly patients mimicing dementia symptoms.

Management for dementia:

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

Medications:

  • 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.
  • Catastrophic reaction is subjective awareness of intellectual deficits in stressful situation result in emotional outburst in dementia patient.
  • Reverslble causes of dementia includes subdural hematoma, normal pressure hydrocephalus, intracranial tumors, intracranial abscess.
  • Alzheimer’s disease is the prototype of cortical dementia.
  • Binswanger’s disease is also known as subcortical arteriosclerotic encephalopathy.
  • Pick’s dlsease 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 tunctions in dementia is done using screening test of mini mental status examination (MMSE).
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