Conditions & Diseases: Brain & Nervous System

Dementia

See Also:
Dementia: Introduction
Dementia: Types
Dementia: Causes & Risk Factors
Dementia: Signs & Symptoms
Dementia: Stages
Dementia: Medical Tests & Diagnosis Methods
Dementia: Treatment & Prevention Options

Types of Dementia

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

I. Cortical Dementia:
Dementia caused due to damage to the cortex or outer layer is 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 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, the dementia that worsens over a period interfering with cognitive abilities is called progressive dementia.

IV. Primary Dementia:
Primary dementia does not result from any other disease for example: Alzheimer’s disease.

V. Secondary Dementia:
Dementia caused due to a physical disease or injury is called secondary dementia (4).

Other types of dementia that fall into more than one of the above types are as follows:

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 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:
It 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, stroke, blood abnormalities, disease in the large blood vessels of the neck and/or disease of the heart valves. The 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 expression 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, migraine 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 due to 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.

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 also one of the types of FTD that develops on 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).

5. 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.

6. Huntington’s Disease (HD):
It 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.

7. 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).

8. 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, pulmonary embolism etc.,

9. Creutzfeldt-Jakob Disease (CJD):
This is a rare, degenerative, fatal brain disorder affecting one person in one million every year worldwide. CJD is believed to be caused due to 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 patients may die due to Pneumonia and other infections.

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

Dementias in Children
Some disorders can lead to dementia in children, which include:

A. Niemann-Pick Disease:
It is a group of inherited disorders affecting the metabolism caused due to “…specific genetic mutations” (4). Patients suffering from this disorder cannot metabolize cholesterol and other lipids leading to accumulation of excessive cholesterol in the liver and spleen and excessive lipids in the brain. Symptoms of the disorder are dementia, confusion and problems with learning and memory.

B. Batten Disease:
It is a fatal, hereditary disorder of the nervous system leading to an accumulation of lipopigments in the body’s tissues. Ultimately, children with this disorder develop dementia, blindness and become bedridden. Symptoms of the disease are personality and behavioral changes, slow learning, clumsiness, stumbling, mental impairment, seizures and progressive loss of sight and motor skills.

C. Lafora Body Disease:
It is a rare genetic disorder leading to seizures, rapid progressive dementia with movement problems. Lafora bodies are microscopic structures present in the brain, skin, liver and muscles of the affected children.

Other disorders that include symptoms of dementia are mitochondrial myopathies, Rasmussen's encephalitis, mucopolysaccharidosis III or Sanfilippo syndrome, neurodegeneration with brain iron accumulation, leukodystrophies such as Alexander disease, Schilder's disease and metachromatic leukodystrophy (4).

See Also:
Dementia: Introduction
Dementia: Types
Dementia: Causes & Risk Factors
Dementia: Signs & Symptoms
Dementia: Stages
Dementia: Medical Tests & Diagnosis Methods
Dementia: Treatment & Prevention Options

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