The 5 Dementias

Dementia Aware: what you need to know about the 5 most common types of dementia

 

Dementia is an umbrella term that describes a progressive neurodegenerative disease causing deterioration in all areas of mental ability and function, accompanied by changes in behaviours and personality. Whilst dementia mainly affects older people, there is growing evidence that that at least 8-10% of cases develop in people ages 40-65 years: frontotemporal dementia, early onset Alzheimer’s disease. Presently, over 46 million people live with dementia worldwide: Asia 22.9 million, Europe 10.5 million, The Americas 9.4 million and Africa 4.0 million. By 2030, this number is estimated to increase to 74.7 million and to 131.5 million by 2050. Around the world, 1 person is diagnosed with dementia every 3 seconds (World Health Organization, 2016).

 

The human brain is an enormously complex structure made up of grey matter and white matter which is found throughout the brain: frontal lobes, temporal lobes, parietal lobes, occipital lobes and cerebellum. Within these lobes are 3 very important areas: hippocampus, limbic system and mid brain.

  • Grey matter is composed of nerve cells (neurons) that communicate with each other by a chemical transmitters (dopamine) situated on the surface of the other neurons involved in regulating memory, mood, sleep, appetite, behaviour. The supporting grey matter (glial cells) supplies nutrients to the neurones and repairs damage; this is very important because, neurons cannot reduplicate themselves and need to be maintained throughout a person’s entire life span.
  • White matter consists of fibres that connect neurones in different parts of the brain to one another allowing rapid communication. These fibres enable neurons to influence the activity of thousands of other neurons in the brain.
  • Frontal lobes influence speech, personality traits, decision making, judgement, behaviours.
  • Temporal lobes regulate memory and mood, the understanding of language and meaning
  • Parietal lobes are involved in motor tasks (cooking, dressing), tactile and visuospatial perception of self and the outside world e.g. location
  • Occipital lobes are at the back of the brain and process visual stimuli
  • Cerebellum is set underneath the main part of brain: controls motor function, language, executive function and working memory
  • Hippocampus: learning of new information
  • Limbic System: memory, behaviour, emotions
  • Mid brain: sleep, appetite, sexual function

Damage to any of these areas will result in the person with dementia developing symptoms specific to that area e.g. limbic system – person may start misplacing items, become suspicious.;

parietal lobe – person may become lost in own home.

 

The 5 most common dementias are: Alzheimer’s disease, vascular dementia, Lewy body dementia, Frontotemporal dementia and Wernicke-Korsakoff’s syndrome:

 

Alzheimer’s Disease:

  • Caused by destruction of neurons due to amyloid plaques and neurofibrillary tangles
  • Damage to limbic system and hippocampus occurs first, then other areas of brain
  • Progressive deterioration in ability to do activities of daily living: dressing, bathing
  • Memory problems, communication difficulties, behavioural and mood disorders
  • Other possible symptoms: insomnia, incontinence, weight loss

Vascular dementia:

  • Usually caused by bleeding/blockages in the blood vessels in the brain e.g. stroke
  • Or by multiple, very small strokes
  • Can occur with other types of dementia e.g. Alzheimer’s disease
  • Early sign is loss of executive function: plan, organize, respond
  • Problems such as decreased mobility, balance problems, depression, urine incontinence are more common
  • Periods of relative stability then a sudden decline, then stability
  • Potential risk factors include high BP, high cholesterol, obesity, smoking, diabetes

Lewy body dementia:

  • Often mistaken for other dementias e.g. Parkinson’s dementia
  • Presence of Lewy bodies: tiny spherical protein deposits that develop inside nerve cells in the areas of thinking, memory and movement
  • Fluctuating cognitive impairment: periods of increased confusion & windows of lucidity
  • Hallucinations or delusions occur frequently and can be quite detailed
  • Spatial disorientation e.g. falls, fainting
  • Tremor, rigidity and slowness of movement
  • Highly sensitive to neuroleptic drugs: Risperidone

Frontotemporal dementia:

  • Most common form of younger onset dementia
  • Affects frontal lobe in brain which controls behaviour and impulse control
  • Mood changes, inflexibility, impulsivity,
  • Hyperorality: excessive smoking or drinking, food fads, putting objects in mouth
  • Changes in behaviour: disinhibition, lack of judgment, loss of social awareness, loss of insight
  • Memory changes occur later

Wernicke-Korsakoff’s Syndrome:

  • Caused by excessive and prolonged alcohol intake
  • Severe vitamin B1 (thiamine) deficiency causes build up of toxins and bleeding into parts of the brain – Wernicke’s Encephalopathy
  • Symptoms (in the absence of intoxication) include: severe confusion, ataxia (walk with feet spread wide apart) and abnormal movement of the eyes
  • Wernicke’s is a medical emergency requiring immediate treatment
  • If treated early, most people will recover, however some will develop Korsakoff’s Syndrome
  • Symptoms of Korsakoff’s include: retrograde amnesia, confabulation (elaborate made up stories), difficulty learning new information, lack of insight and general disinterest in things
  • With prolonged abstinence from alcohol, there may be a partial recovery in symptoms

Other dementias include: Parkinson’s Disease with dementia, mixed dementia, Chronic Traumatic Encephalopathy, Progressive Supranuclear Palsy, Neuro-Syphilis dementia, and Progressive Non-Fluent Aphasia.

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