DEMENTIA

DEMENTIA

Introduction:

• 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. 

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 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.

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 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.

Medications:

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

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