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Причины деменции

Деменция включает поражение нервных клеток в мозге, которое может произойти в различных его частях. Деменция может по-разному протекать у разных людей, в зависимости от пораженной области мозга.

Деменция может быть классифицированна различными путями, различные формы деменции обычно объединяются в группы по области поражения мозга или по степени прогрессирования болезни.

Некоторые виды деменции, например, вызванные реакцией на медикаменты или инфекцию, поддаются лечению.

Прогрессирующие деменции

Разновидности деменции, которые не поддаются восстановлению и ухудшаются с течением времени:

  • Болезнь Альцгеймера. Среди людей старше 65 лет болезнь Альцгеймера является лидирующей формой деменции. Ее симптомы начинают проявляться после 60 лет, хотя у некоторых это может происходить раньше в связи с наличием дефектных генов.Хотя в большинстве случаев точную причину болезнь Альцгеймера установить невозможно, обычно ее появление связано с белковыми бляшками в мозге.

    Некоторые генетические факторы могут также расположить человека к развитию болезни Альцгеймера.

    Обычно болезнь Альцгеймера прогрессирует медленно на протяжении 8-10 лет. Когнитивные способности ухудшаются постепенно. В конечном итоге определенные части мозга, ответственные за память, речь и суждения, перестают работать правильно.

  • Сосудистая деменция. Сосудистая деменция — вторая по распространенности форма деменции, возникает в результате повреждения клеток мозга, вызванного недостаточным кровообращением в сосудах, ведущих в мозг.Нарушение функции сосудов может быть вызвано инсультом, инфекцией сердечного клапана (эндокардит) или другими заболеваниями сосудов.

    Симптомы обычно появляются внезапно и распространены среди людей с повышенным давлением, уже перенесших ранее инфаркт или инсульт.

    Several different types of vascular dementia exist, and the types have different causes and symptoms. Alzheimer’s disease and other dementias also may be present at the same time as this dementia.

  • Lewy body dementia. Lewy body dementia affects approximately 10 percent of people with dementia, making it one of the most common types of dementia. Lewy body dementia becomes more common with age.Lewy bodies are abnormal clumps of protein that have been found in the brains of people with Lewy body dementia, Alzheimer’s disease and Parkinson’s disease.

    Lewy body dementia symptoms are similar to symptoms of Alzheimer’s disease. Its unique features include fluctuations between confusion and clear thinking (lucidity), visual hallucinations, and tremor and rigidity (parkinsonism).

    People with Lewy body dementia often have a condition called rapid eye movement (REM) sleep behavior disorder that involves acting out dreams.

  • Frontotemporal dementia. This type of dementia tends to occur at a younger age than does Alzheimer’s disease, generally between the ages of 50 and 70.This is a group of diseases characterized by the breakdown (degeneration) of nerve cells in the frontal and temporal lobes of the brain, the areas generally associated with personality, behavior and language.

    Signs and symptoms of frontotemporal dementia can include inappropriate behaviors, language problems, difficulty with thinking and concentration, and movement problems.

    As with other dementias, the cause isn’t known, although in some cases this dementia is related to certain genetic mutations.

Other disorders linked to dementia

  • Huntington’s disease. This inherited disease causes certain nerve cells in your brain and spinal cord to waste away.Signs and symptoms usually appear during your 30s or 40s. People may experience personality changes, such as irritability or anxiety.

    The condition causes a severe decline in thinking (cognitive) skills over time. Huntington’s disease also causes weakness and difficulty with walking and movement.

  • Traumatic brain injury. This condition is caused by repetitive head trauma, such as experienced by boxers, football players or soldiers.Depending on the part of the brain that’s injured, this condition can cause dementia signs and symptoms such as uncoordinated movement and impaired speech, as well as slow movement, tremors and rigidity (parkinsonism). Symptoms may not appear until many years after the actual trauma.

    A person who has experienced a single traumatic head injury could develop a similar condition called posttraumatic dementia, which may cause symptoms such as long-term memory problems.

  • Creutzfeldt-Jakob disease. This rare brain disorder usually occurs in people without risk factors. This condition may be due to an abnormal form of a protein. Creutzfeldt-Jakob disease sometimes may be inherited or caused by exposure to diseased brain or nervous system tissue.Signs and symptoms of this fatal condition usually appear around age 60 and initially include problems with coordination, memory, thinking and vision. Symptoms worsen over time and may include the inability to move or talk, blindness, or infections.
  • Parkinson’s disease. Many people with Parkinson’s disease eventually develop dementia symptoms (Parkinson’s disease dementia).

Dementia-like conditions that may be reversed

Some causes of dementia or dementia-like symptoms can be reversed. Your doctor may identify and treat these causes:

  • Infections and immune disorders. Dementia-like symptoms can result from fever or other side effects of your body’s attempt to fight off an infection.People may develop thinking difficulties if they have brain infections like meningitis and encephalitis, untreated syphilis, Lyme disease, or conditions that cause a completely compromised immune system, such as leukemia.

    Conditions such as multiple sclerosis that arise from the body’s immune system attacking nerve cells also can cause dementia.

  • Metabolic problems and endocrine abnormalities. People with thyroid problems, too little sugar in the bloodstream (hypoglycemia), too low or too high amounts of sodium or calcium, or an impaired ability to absorb vitamin B-12 may develop dementia-like symptoms or other personality changes.
  • Nutritional deficiencies. Dementia-like symptoms can occur as a result of not drinking enough liquids (dehydration); not having enough thiamin (vitamin B-1), a condition common in people with chronic alcoholism; and not having enough vitamins B-6 and B-12 in your diet.
  • Reactions to medications. Dementia-like symptoms may occur as a reaction to a single medication or because of an interaction of several medications.
  • Subdural hematomas. Subdural hematomas are caused by bleeding between the surface of the brain and the covering over the brain. They can cause symptoms similar to dementia.
  • Poisoning. Dementia-like symptoms can occur as a result of exposure to heavy metals, such as lead, and other poisons, such as pesticides.Dementia-like symptoms may also occur in some people who have abused alcohol or recreational drugs. Symptoms may disappear after treatment, but in some cases symptoms may still be present after treatment.
  • Brain tumors. Dementia rarely can result from damage caused by a brain tumor.
  • Anoxia. This condition, also called hypoxia, occurs when organ tissues aren’t getting enough oxygen. Anoxia may occur due to severe asthma, heart attack, carbon monoxide poisoning or other causes.If you’ve experienced a severe lack of oxygen, recovery may take longer. Symptoms, such as memory problems or confusion, may occur during recovery.
  • Normal-pressure hydrocephalus. Sometimes people have a condition caused by enlarged ventricles in the brain (normal-pressure hydrocephalus). This condition can cause walking problems, urinary difficulty and memory loss.Shunt surgery, which delivers cerebrospinal fluid from the head to the abdomen or heart, may help these symptoms.

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