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What are the different Types of Dementias

Vascular dementia

Vascular dementia is the second most common dementia after Alzheimer's Diseas. 1 in five of people with dementia has this type.

It follows an illness of the blood vessels of the brain, usually in those suffering from hardening of the lining of the blood vessels which is known medically as Atherosclerosis. The patient usualy has a long history of high cholestrol level and high blood pressure before any signs of dementia. Mini-strokes ushers the arrival of dementia . The symptoms of dementia depend on the place of the strokes, and whether the blood vessels affected were large or small. Multiple brain injuries from repeated small or large strokes can cause progressive dementia over time. Even a single small injury to a critically important area critical for cognition such as the hippocampus, or thalamus, can lead to sudden cognitive decline. Sometimes, vascular changes can add the picture of Alzhiemer's disease, and the picture may be that of mixed symptoms.

Brain scans may show evidence of multiple strokes of different sizes in various locations. A person who suffer from vascular dementia tend to have history of a disease that affect the blood vessels, such as chronic tobacco use, high blood pressure, atrial fibrillation, high cholesterol levels, diabetes, or history of previous heart attack or angina.

Lewy body dementia

This type of dementia shows early signs of mild impairment of intellectual and cognitive functions, but there are more prominent episodes of delirium and confusion. It is the third most common type od dementia after Alzheimer's and Mult-Infarct dentias. The symptoms are frequent, fluctuating, more severe than in the other types of dementia. Cognition, alertness or attention vary from time to time. Sleep problems like night terrors, enacting dreams, or waking up confused and delirious are characteristic. Some patients may have symptoms of parkinsonism like rigidity of the muscles, slowness, shakiness and proneness to falls. This is usually not related to medication or stroke which may also cause rigidity or shakiness.

Repeated visual hallucinations are a common feature in Lewy body dementia. The visual hallucinations are vivid imagery of people or animals, and they often occur when the person is about to fall asleep or to wake up. Other salient symptoms include problems with planning or executive functions. For example, for cooking a meal, you have to get the right ingredients, prepare them well, cooking them on a source of heat, adjusting the heat level, monitoring them when they are ready, and removing them from heat and remember to shut the stove or cooker. This is an example of the executive functions of the brain.

Difficulty with visual-spatial function also lead to disorientation and difficulty in finding the way around. Disruption in autonomic bodily functions are striking: falls and fainting due to drop in blood pressure, difficulty emptying the urinary bladder or bowel, lack of sweating or profuse sweating, numbness, tingling, aches and pains, and dizziness..etc.

Abnormal sleep and dream behaviors may begin before cognitive decline is observed. These are are a core feature of dementia of Lewy bodies. This type of dementia is diagnosed either by sleep study recording or, when sleep studies cannot be performed, by medical history and validated questionnaires.

Parkinson's disease dementia

Parkinson's disease is a Lewy body disease that often progresses to Parkinson's disease dementia following a period of dementia-free Parkinson's disease.

Frontotemporal dementia(FTD)

The frontal lobe of the brain is the area of the brain behind the forehead, while the temporal lobe is the area behind the skull region above the ears. In this type of dementia there is progressive damage to these two areas of the brain.

Because the frontal and tempral lobes are important areas for judgement, thinking and behaviour; Frontotemporal Dementia is characterized by drastic personality changes and language difficulties. The person become socially withdrawan early in the illness and does not realize there is any change in his behaviour (lack of insight). Memory problems are not the main feature here. There are more than one types of FTD. The behavioral subtype is the most common with symptoms of change in personality and behavior. The hallmark feature the behavioural type is impulsive behaviour: the person shows a change in personal hygiene, becomes rigid in thinking, and rarely acknowledges the problems. They are socially withdrawn, and often have a drastic increase in appetite. Those patients may become socially inappropriate. For example, they may make inappropriate sexual comments, or may begin using pornography openly. One of the most common signs is apathy, or not caring about anything. Apathy, however, is a common symptom in many dementias.

Another two types of FTD feature language problems as the main symptom; in the form of not finding the right words when needed (aphasia). In the semantic subtype, there is progressive aphasia. The main feature is loss of the meaning of words. It may begin with difficulty naming things. The person eventually may lose the meaning of objects as well. For example, if asked to draw a bird, a dog, and an airplane he may draw the same thing three times. Or if you show the patient a picture of one of these thing, he will call them all the same: A dog picture will be called an airplane. They all appear almost the same to him.

In a classic test for this semantic deficit, a patient is shown a picture of a pyramid and below it a picture of both a palm tree and a pine tree. The person is asked to say which one goes best with the pyramid. The person cannot answer that question.

In another subtype, there is loss of all fluency, grammar, and problems with producing speech. Those patients have trouble finding the right words, but they also have a difficulty coordinating the muscles needed to speak. Eventually, they only uses one-syllable words or may become totally mute. A frontotemporal dementia is associated with loss of motor functions.

Huntington's disease dementia

Huntington disease (HD) is a genetic disease due to a dominant gene which leads to degeneration of the nerve cells in the nervous system and the brain. Genes carry the genetic code in two pairs of similar chromosomes. A dominant gene is one that show its effect even if its identical pair does not have that same gene. All offsprings of an affected person will have the condition, no one is spared. The dominant gene override a similar healthy gene on its identical chromosome. Humans have 23 identical pairs of chromosomes, 46 chromsomes in total. two of these are sex chromosomes: xx in a female and xy in a male.

This disease is characterized by abnormalities of movement that appear as involunatry body gestures . The person moves his arms and legs unwillingly in way which seems like dancing (This is called chorea; Greek for dancing). The condition may end in progressive dementia, and psychiatric and behavioral disturbance. In 1872, George Huntington, descibed a disease featuring "hereditary nature, adult onset, chorea, and mind impairment,". He also noticed that it has "a tendency to insanity and suicide." Although Huntington was not the first to describe this "dancing mania", his account was so comprehensive that he received international recognition.

Symptoms of Huntington disease include cognitive impairment which usually declines further into dementia.

HIV-associated dementia

HIV infection or AIDS is associated with dementia at a late stage of the illness. In contrast to other dementias most of the patients are younger people. It is mainly a dementia with outstanding cognitive impairment accompanied by motor disability, speech problems and behavioral change. The mental damage is characterised by mental slowness, trouble with memory and poor concentration. Motor symptoms include a loss of fine motor control leading to clumsiness, poor balance and tremors. Behavioral changes may include apathy, lethargy and diminished emotional responses and lack of spontaneity. These symptoms are a result of infiltration of white blood cells monocytes and macrophages into the central nervous system to combat the virus. This will bring about scarring in the brain (gliosis), damage to the nerve cell structures, and loss of neurones.

Dementia due to prion disease

This is a strange rapidly fatal type of dementia which is sometimes transmitted through generations either through genes or through a particular protein known as prion. The disease is also known as Creutzfeldt-Jakob disease after the doctors who described it. The dementia worsens over weeks to months and most patients die within a year. Symptoms in the early stage include memory problems, behavioral changes, poor coordination, and visual disturbances. Later dementia develops, with involuntary movements, blindness, weakness, and coma.

This type of dementia is related to the mad cow disease (bovine spongiform encephalopathy). Most cases are not inherited but this is very rare: the rate of incidence is one per million. The prion protein, although not a live material, still can cause infection. Transmision of brain tissue occaisonally takes place in surgical procedures; like brain tissue transplants or injection of hormones extracted from cadevers. The practice of cannibalism in one Papua New Guinea tribe lead to the spread of a fatal brain disease called kuru. This was a devastating epidemic, very similar to Creuzfeldt-Jakob disease, that occured in these tribes which had the bizarre practice of eating the brains of their elderly deceased as a form of liberating their souls.

Alcohol-related dementia

Many years of excessive alcohol or even substance abuse may lead to brain damage and consequent dementia. Alcohol and its toxic by-products can cause the slow and gradual brain damage. Other factors can be involved in this development of brain damage; including thiamine (Vitamin B1) deficiency. Older alcoholics are more vulnerable to brain damage. Loss of brain cells is more notable, with greater cognitive impairments in those over aged 65 years. A degree of brain damage is seen in more than 70% of those with alcohol use disorder. Brain regions affected are similar to those that are affected by aging, and also by Alzheimer's disease. Regions showing loss of volume include the frontal, temporal, and parietal lobes, the cerebellum, thalamus, and hippocampus.

Mixed dementia

More than one type of dementia may co-exist in about 10% of people affected. The most common mixed dementia is a combined Alzheimer's disease and vascular dementia. This particular mix of the two dementias may arise from combined factors like old age, high blood pressure, and damage to blood vessels in the brain.

Diagnosis of mixed dementia can be difficult, as often only one type will predominate. This makes the treatment of people with mixed dementia uncommon, with many people missing out on potentially helpful treatments. Mixed dementia can mean that symptoms set off earlier, and worsen more quickly since more parts of the brain are affected by both the vascular changes and the degeneration of neurons.

Dementia caused by Other conditions

Chronic inflammatory conditions that may affect the brain and cognition include Behcet's disease: an auto-immune inflammatory disease that affects the vessels in many organs inside the body. Multiple autoimmune diseases can also cause dementias. These types of dementias can rapidly progress, but usually have a good response to early treatment. Treatment consists of modulators of the immune system or steroid administration, or in certain cases, the elimination of the causative agent.

Celiac disease, a long-term autoimmune disorder that primarily affects the small intestine, may be associated with Alzheimer's disease, vascular dementia, and frontotemporal dementia. A strict gluten-free diet started early may protect against dementia associated with this type of gluten-related disorder.

Dementia may be reversible in those cases caused by physical treatable conditions like : underactive thyroid (hypothyroidism), vitamin B12 deficiency, or infectious diseases such as Lyme disease, and Syphilis affecting the nervous system.

Many other medical and neurological conditions result in dementia only late in the illness. For example, some patients with Parkinson's disease develop dementia. When dementia occurs in Parkinson's disease, the brain shows evidence of dementia with Lewy bodies or Alzheimer's disease, or both.

Acute porphyrias is a genetic hereditary disease of the liver which make it fails to metabolise some toxic internal byproducts of metablism and external substances including some drugs. These unchecked toxins can affect the nervous system in various ways. It may cause episodes of confusion and psychiatric disturbance. dementia is uncommon feature of these rare diseases. Hereditary disorders that can also cause dementia include other some metabolic disorders.


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