Dementia
- What is Dementia?
- What Are the Different Kinds of Dementia?
- What Causes Dementia?
- Is there any treatment?
- What is the prognosis?
- What research is being done?
Dementia is not a specific disease. Dementia disease is a descriptive term for a collection of symptoms that can be caused by a number of disorders that affect the brain. People with dementia disorder have significantly impaired intellectual functioning that interferes with normal activities and relationships. They also lose their ability to solve problems and maintain emotional control, and they may experience personality changes and behavioral problems, such as agitation, delusions, and hallucinations. While memory loss is a common symptom of dementia, memory loss by itself does not mean that a person has dementia. Doctors do dementia treatment only if two or more brain functions - such as memory and language skills -- are significantly impaired without loss of consciousness. Some of the diseases that can cause symptoms of dementia are Alzheimer’s disease, vascular dementia, Lewy body dementia, frontotemporal dementia, Huntington’s disease, and Creutzfeldt-Jakob disease. Doctors have identified other conditions of dementia causes or dementia-like symptoms including reactions to medications, metabolic problems and endocrine abnormalities, nutritional deficiencies, infections, poisoning, brain tumors, anoxia or hypoxia (conditions in which the brain’s oxygen supply is either reduced or cut off entirely), and heart and lung problems. Although it is common in very elderly individuals, dementia types is not a normal part of the aging process.
What Are the Different Kinds of Dementia?
Dementing disorders can be classified many different ways. These classification schemes attempt to group disorders that have particular features in common, such as whether they are progressive or what parts of the brain are affected. Some frequently used classifications include the following:
- Cortical dementia - dementia where the brain damage primarily affects the brain's cortex, or outer layer. Cortical dementias tend to cause problems with memory, language, thinking, and social behavior.
- Subcortical dementia - dementia that affects parts of the brain below the cortex. Subcortical dementia tends to cause changes in emotions and movement in addition to problems with memory.
- Progressive dementia - dementia that gets worse over time, gradually interfering with more and more cognitive abilities.
- Primary dementia - dementia such as AD that does not result from any other disease.
- Secondary dementia - dementia that occurs as a result of a physical disease or injury.
Secondary Dementias
Dementia disease may occur in patients who have other disorders that primarily affect movement or other functions. These cases are often referred to as secondary dementias. The relationship between these dementia disorders and the primary dementias is not always clear. For instance, people with advanced Parkinson's disease, which is primarily a movement disorder, sometimes develop symptoms of dementia. Many Parkinson's patients also have amyloid plaques and neurofibrillary tangles like those found in AD. The two diseases may be linked in a yet-unknown way, or they may simply coexist in some people. People with Parkinson's and associated dementia sometimes show signs of Lewy body dementia or progressive supranuclear palsy at autopsy, suggesting that these diseases may also overlap with Parkinson's or that Parkinson's is sometimes misdiagnosed.
Other disorders that may include symptoms of dementia include multiple sclerosis; presenile dementia with motor neuron disease, also called ALS dementia; olivopontocerebellar atrophy (OPCA); Wilson's disease; and normal pressure hydrocephalus (NPH).
Dementias in Children
While it is usually found in adults, dementia can also occur in children. For example, infections and poisoning can lead to dementia causes in people of any age.In addition, some disorders unique to children can cause dementia.
Niemann-Pick disease is a group of inherited disorders that affect metabolism and are caused by specific genetic mutations. Patients with Niemann-Pick disease cannot properly metabolize cholesterol and other lipids. Consequently, excessive amounts of cholesterol accumulate in the liver and spleen and excessive amounts of other lipids accumulate in the brain. Symptoms may include dementia, confusion, and problems with learning and memory. These diseases usually begin in young school-age children but may also appear during the teen years or early adulthood.
Batten disease is a fatal, hereditary disorder of the nervous system that begins in childhood. Symptoms are linked to a buildup of substances called lipopigments in the body's tissues. The early symptoms of dementia disease include personality and behavior changes, slow learning, clumsiness, or stumbling. Over time, affected children suffer mental impairment, seizures, and progressive loss of sight and motor skills. Eventually, children with Batten disease develop dementia and become blind and bedridden. The disease is often fatal by the late teens or twenties.
Lafora body disease is a rare genetic disease that causes seizures, rapidly progressive dementia, and movement problems. These problems usually begin in late childhood or the early teens. Children with Lafora body disease have microscopic structures called Lafora bodies in the brain, skin, liver, and muscles. Most affected children die within 2 to 10 years after the onset of symptoms.
A number of other childhood-onset disorders can include symptoms of dementia. Among these are mitochondrial myopathies, Rasmussen's encephalitis, mucopolysaccharidosis III (Sanfilippo syndrome), neurodegeneration with brain iron accumulation, and leukodystrophies such as Alexander disease, Schilder's disease, and metachromatic leukodystrophy
What Causes Dementia?
All forms of dementia result from the death of nerve cells and/or the loss of communication among these cells. The human brain is a very complex and intricate machine and many factors can interfere with its functioning. Researchers have uncovered many of these factors, but they have not yet been able to fit these puzzle pieces together in order to form a complete picture of how dementias develop.
Many types of dementia, including AD, Lewy body dementia, Parkinson's dementia, and Pick's disease, are characterized by abnormal structures called inclusions in the brain. Because these inclusions, which contain abnormal proteins, are so common in people with dementia, researchers suspect that they play a role in the development of symptoms of dementia. However, that role is unknown, and in some cases the inclusions may simply be a side effect of the disease process that leads to the dementia.
Genes clearly play a role in the development of some kinds of dementia. However, in AD and many other disorders, the dementia usually cannot be tied to a single abnormal gene. Instead, these forms of dementia appear to result from a complex interaction of genes, lifestyle factors, and other environmental influences.
Researchers have identified several genes that influence susceptibility to AD. Mutations in three of the known genes for AD - genes that control the production of proteins such as amyloid precursor protein (APP), presenilin 1, and presenilin 2 - are linked to early-onset forms of the disease.
Variations in another gene, called apolipoprotein E (apoE), have been linked to an increased risk of late-onset AD. The apoE gene does not cause the disease by itself, but one version of the gene, called apoE epsilon4 (apoE E4), appears to increase the risk of AD. People with two copies of the apoE E4 gene have about ten times the risk of developing AD compared to people without apoE E4. This gene variant seems to encourage amyloid deposition in the brain. One study also found that this gene is associated with shorter survival in men with AD. In contrast, another version of the apoE gene, called apoE E2, appears to protect against AD.
Studies have suggested that mutations in another gene, called CYP46, may contribute to an increased risk of developing late-onset sporadic AD. This gene normally produces a protein that helps the brain metabolize cholesterol.
Scientists are trying to determine how beta amyloid influences the development of AD. A number of studies indicate that the buildup of this protein initiates a complex chain of events that culminates in dementia. One study found that beta amyloid buildup in the brain triggers cells called microglia, which act like janitors that mop up potentially harmful substances in the brain, to release a potent neurotoxin called peroxynitrite. This may contribute to nerve cell death in AD. Another study found that beta amyloid causes a protein called p35 to be split into two proteins. One of the resulting proteins triggers changes in the tau protein that lead to formation of neurofibrillary tangles. A third study found that beta amyloid activates cell-death enzymes called caspases that alter the tau protein in a way that causes it to form tangles. Researchers believe these tangles may contribute to the neuron death in AD.
Vascular dementia can be caused by cerebrovascular disease or any other condition that prevents normal blood flow to the brain. Without a normal supply of blood, brain cells cannot obtain the oxygen they need to work correctly, and they often become so deprived that they die.
The causes of other types of dementias vary. Some, such as CJD and GSS, have been tied to abnormal forms of specific proteins. Others, including Huntington's disease and FTDP-17, have been linked to defects in a single gene. Post-traumatic dementia is directly related to brain cell death after injury. HIV-associated dementia is clearly tied to infection by the HIV virus, although the exact way the virus causes damage is not yet certain. For other dementias, such as corticobasal degeneration and most types of frontotemporal dementia, the underlying causes have not yet been identified.
Is there any treatment?
Drugs to specifically treat Alzheimer’s disease and some other progressive dementias are now available. Although these drugs do not halt the disease or reverse existing brain damage, they can improve symptoms and slow the progression of the disease. This may improve an individual’s quality of life, ease the burden on caregivers, or delay admission to a nursing home. Many researchers are also examining whether these drugs may be useful for treating other types of dementia. Many people with dementia, particularly those in the early stages, may benefit from practicing tasks designed to improve performance in specific aspects of cognitive functioning. For example, people can sometimes be taught to use memory aids, such as mnemonics, computerized recall devices, or note taking.
What is the prognosis?
There are many disorders that can cause dementia disorder. Some, such as Alzheimer’s disease or Huntington’s disease, lead to a progressive loss of mental functions. But other types of dementia can be halted or reversed with appropriate treatment. People with moderate or advanced dementia typically need round-the-clock care and supervision to prevent them from harming themselves or others. They also may need assistance with daily activities such as eating, bathing, and dressing.
What research is being done?
The National Institute of Neurological Disorders and Stroke (NINDS) and other institutes of the National Institutes of Health (NIH) conduct research related to dementia in laboratories at the NIH and also support additional dementia symptoms research through grants to major medical institutions across the country. Current research focuses on many different aspects of dementia disease. This research promises to improve the lives of people affected by the dementias and may eventually lead to ways of preventing or curing these disorders.
Information Obtained From National Institute Of Health