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
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).
- Alzheimers disease
- Vascular dementia
- Lewy body dementia
- Frontotemporal dementia
- Pick's Disease
- HIV-associated dementia
- Huntington's disease
- Dementia pugilistica
- Corticobasal degeneration
- Creutzfeldt-Jakob 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
2). Binswangers 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.
Binswangers 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.
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
3. Lewy Body Dementia (LBD):
Lewy Body Dementia (LBD) is caused by the death of cells in the brains
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 Alzheimers 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. Picks 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.
6. HIV-Associated Dementia (HAD):
As the name indicates, HAD is due to an infection of human immunodeficiency
virus (HIV) destroying the brains white matter ultimately leading
to dementia. The symptoms include impaired memory, apathy, social withdrawal,
difficulty in concentrating and movement.
7. Huntingtons Disease (HD):
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
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).
9. Corticobasal Degeneration (CBD):
CBD is a progressive disorder marked by loss of nerve cells and
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
•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
Article by Kona Vishnu, MS
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