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Dementia

See Also:
Dementia: Introduction
Dementia: Types
Dementia: in Children
Dementia: Causes & Risk Factors
Dementia: Signs & Symptoms
Dementia: Stages
Dementia: Medical Tests & Diagnosis Methods
Dementia: Treatment & Management

Types of Dementia

There are different ways to classify dementing disorders based on common features, in terms of their progressive nature, and parts of the brain affected. These dementia types include:

I. Cortical Dementia:
Dementia caused by damage to the cortex or outer layer is called cortical dementia. “Cortical dementias tend to cause problems with memory, language, thinking and social behavior.” (4)

II. Subcortical Dementia:
Dementia affecting parts of the brain below the cortex is subcortical dementia. This type “… causes changes in emotions and movement in addition to problems with memory” (4).

III. Progressive Dementia:
As the name indicates, dementia that worsens over time and interferes with cognitive abilities is called progressive dementia.

IV. Primary Dementia:
Primary dementia does not result from any other disease. Those dementia's which are considered primary include: (See explanations below list).

  1. Alzheimer’s disease
  2. Vascular dementia
  3. Lewy body dementia
  4. Frontotemporal dementia
  5. Pick's Disease
  6. HIV-associated dementia
  7. Huntington's disease
  8. Dementia pugilistica
  9. Corticobasal degeneration
  10. Creutzfeldt-Jakob disease :

1. Alzheimer's Disease:
Alzheimer's disease is the most common form of dementia affecting 10% of the people above 65 years of age and 50% people over 85. The disease is caused due to irreversible progressive deterioration of brain cells, especially the cerebral cortex and hippocampus, causing loss of cognitive functions such as memory, movement coordination, pattern recognition, judgment and reasoning (5).

2. Vascular Dementia:
Vascular Dementia is the second most common cause of dementia accounting for about 20% of all cases. Damage to the brain due to cerebrovascular or cardiovascular strokes are the main causes. Vascular dementia has 3 subtypes with varying causes and symptoms.

 

1). Multi Infarct Dementia (MID):
MID is caused by a number of small strokes leading to multiple damaged areas and lesions in the white matter or nerve fibers of the brain. It is important to note that “…not all strokes cause dementia, in some cases a single stroke can damage to the brain enough to cause dementia.” (4) Dementia from a single stroke damages either the left side of the brain or hippocampus and is called single infarct dementia.

2). Binswanger’s Disease:
This is a rare type of dementia caused by damage to small blood vessels in the white matter of brain. People suffering from this disease have abnormal blood pressure, strokes, blood abnormalities, disease in the large blood vessels of the neck and/or disease of the heart valves. Binswanger’s disease leads to lesions in the brain, memory loss, disordered cognition and changes in mood. Symptoms such as urinary incontinence, difficulty in walking, clumsiness, slowness, lack of facial expressions and speech difficulty are prominent.

3). CADASIL:
Vascular dementia of this type is a rare hereditary disorder abbreviated as Cerebral Autosomal Dominant Arteriopathy with SubCortical Infarct and Leukoencephalopathy. “CADASIL is linked to abnormalities of a specific gene, Notch3, which is located on chromosome 19.” (4) CADASIL causes strokes with multi-infarct dementia, migraines with aura and mood disorders.

Vascular dementia may also be caused due to inflammation of the blood vessel system (Vasculitis), low blood pressure and lesions due to brain hemorrhage.

3. Lewy Body Dementia (LBD):
Lewy Body Dementia (LBD) is caused by the death of cells in the brain’s cortex and part of the mid-brain (Substantia nigra) with many remaining mid-brain nerve cells containing abnormal structures called Lewy bodies. A protein called alpha-synuclein contained in these Lewy bodies causes several disorders collectively called Synucleinopathies. Symptoms of LBD overlap with those of Alzheimer’s disease and typically include visual hallucinations, parkinsonian symptoms and day-to-day fluctuations in the severity of symptoms.

4. Frontotemporal Dementia (FTD) or Frontal Lobe Dementia:
FTD is a group of diseases caused by the degeneration of nerve cells in the frontal and temporal lobes of the brain. There is an abnormal formation of tau protein in these regions of the brain accumulating into neurofibrillary tangles and disrupting normal cell activities, thus ultimately leading to death of cells.

People suffering from FTD do not maintain normal interactions and follow social conventions. Other symptoms such as loss of speech, language, compulsive or repetitive behavior, increased appetite and motor problems (stiffness and balance), are common in FTD.

5. Pick’s disease is a type of FTD in which the nerve cells are composed of Pick bodies containing the protein tau inside the typically swollen or ballooned neurons. The symptoms of the disease include inappropriate social behavior, loss of mental flexibility, language problems and difficulty in thinking and concentration.

Primary progressive aphasia (PPA) is another type of FTD that happens to develop in people in their early forties. In PPA, one or more of the functions such as deficit in language, speaking, understanding and naming common objects are gradually impaired over a period time. “Many, but not all, people with PPA eventually develop symptoms of dementia.” (4)

6. HIV-Associated Dementia (HAD):
As the name indicates, HAD is due to an infection of human immunodeficiency virus (HIV) destroying the brain’s white matter ultimately leading to dementia. The symptoms include impaired memory, apathy, social withdrawal, difficulty in concentrating and movement.

7. Huntington’s Disease (HD):
Huntington’s Disease is a hereditary disorder caused by a faulty gene for protein Huntington leading to degeneration of many regions of brain and spinal cord. Symptoms of the disorder appear in patients aged 30 to 40 years with average life expectancy being about 15 years. Symptoms of the disease include mild personality changes, irritability, anxiety, depression, psychotic behavior, chorea, arrhythmic movements of the body, muscle weakness, clumsiness, gait disturbances and progress to severe dementia.

8. Dementia Pugilistica or Chronic Traumatic Encephalopathy or Boxer’s Syndrome:
Dementia due to head trauma caused by head injury during boxing is called Dementia Pugilistica. Common symptoms such as dementia and Parkinsonism appear many years after the trauma. Other common symptoms include poor coordination and slurred speech. “A single traumatic brain injury may also lead to a disorder called post-traumatic dementia (PTD).” (4)

9. Corticobasal Degeneration (CBD):
CBD is a progressive disorder marked by loss of nerve cells and “…atrophy of multiple areas of the brain.” (4) Symptoms include poor coordination, rigidity, memory loss, dementia, visual-spatial problems, apraxia (i.e., loss of the ability to make familiar, purposeful movements), hesitant and halting speech, myoclonus (i.e., involuntary muscular jerks) and dysphagia (i.e., difficulty in swallowing). Generally, death occurs due to secondary problems such as pneumonia, sepsis, and pulmonary embolism.

10. Creutzfeldt-Jakob Disease (CJD):
This is a rare, degenerative, and fatal brain disorder affecting one person in one million every year worldwide. CJD is believed to be caused by an abnormal form of protein named prion. Symptoms include problems with muscular coordination, personality changes, impaired memory, judgment and thinking, impaired vision, insomnia, depression and myoclonus. Finally, the patient may die due to Pneumonia and other infections.

V. Secondary Dementia:
Dementia caused by physical disease or injury is called secondary dementia. Some examples include:

•Progressive supranuclear palsy
•Multiple Sclerosis
•ALS dementia (Amyotrophic Lateral Sclerosis), also referred to as Lou Gehrig's disease.
•Normal pressure dementia

“Other rare hereditary dementias include Gerstmann-Straussler-Scheinker (GSS) disease, fatal familial insomnia, familial British dementia, and familial Danish dementia.” (4)

See also: Dementia in Children

See Also:
Dementia: Introduction
Dementia: Types
Dementia: in Children
Dementia: Causes & Risk Factors
Dementia: Symptoms, Tests & Diagnosis
Dementia: Stages, Treatment & Prevention

Article by Kona Vishnu, MS
Medical Writer,
OmniMedicalSearch.com

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Page Last Modified:
03/06/2011