Causes of Dementia

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Causes of Dementia




Causes of Dementia

Dementia is a decline or loss of reasoning, memory, and other mental abilities (the cognitive functions such as judgment, thinking, behaviour, and language) and is not a normal part of aging. This decline is progressive and eventually impairs the ability to carry out everyday activities such as driving; household chores; and even personal care such as bathing, dressing, and feeding (often called activities of daily living).

In classifying dementias, broadly into reversible and irreversible dementias.



Irreversible Causes of Dementia?


Alzheimer’s disease:

This is the most common cause of dementia, accounting for about half of all cases. In this disease, abnormal protein deposits in the brain destroy cells in the areas of the brain that control memory and mental functions. People with Alzheimer’s disease also have lower-than-normal levels of brain chemicals called neurotransmitters that control important brain functions. Alzheimer’s disease is not reversible, and no known cure exists. However, certain medications can retards  its progress.

Dementia with Lewy bodies(DLB)

DLB  is caused by abnormal microscopic deposits of protein, called Lewy bodies, which destroy nerve cells. These deposits can cause symptoms typical of Parkinson’s disease, such as tremor and muscle rigidity, bradykinesiaas well as dementia similar to that of Alzheimer’s disease. DLB  affects thinking, attention, and concentration more than memory and language. Like Alzheimer’s disease, Lewy body dementia is not reversible and has no known cure.


It is the second most common cause of dementia, accounting for as many as 40% of cases. This dementia is caused by atherosclerosis, or “hardening of the arteries,” in the brain tissue. Deposits of fats, dead cells, and other debris form on the inside of arteries, partially (or completely) blocking blood flow causing multiple strokes or “infarction,” this type of dementia is sometimes called multi-infarct dementia. One subtype whose origin is not well understood is Binswanger disease. Vascular dementia is related to high blood pressure, dyslipidemia, cvd, diabetes, and related conditions. Treating those conditions can slow the progress of vascular dementia, but functions do not come back once they are lost.


Parkinson’s disease:

People with this disease typically have limb stiffness rigidity (which causes them to shuffle when they walk), speech problems, andresting  tremor (shaking at rest). Dementia may develop late in the disease called as parikinson disease dementia (PDD), but not everyone with Parkinson’s disease has dementia. Reasoning, memory, speech, and judgment are most likely to be affected.

Huntington’s disease:

This inherited disease causes wasting of certain types of brain cells k/as caudate nucleus that control movement as well as thinking. Dementia is common and occurs in the late stages of the disease. Personality changes are typical. Reasoning, memory, speech, and judgment may also be affected.

Creutzfeldt-Jakob disease: CJD

This rare disease occurs most often in young and middle-aged adults. Infectious agents called prions invade and kill brain cells, leading to behaviour changes and memory loss, myoclonic jerks. The disease progresses rapidly and is fatal.

Pick disease or FTD

(Frontotemporal dementia): Frontotemporal dementia is another rare disorder that damages cells in the frontal and/or temporal part of the brain. Behaviour and personality changes usually precede memory loss and language problems.

Untreated brain infections

(for example, HIV, Lyme disease) damage brain cells by forming lesions and trigger inflammatory responses that damage or kill brain cells.

Wernicke-Korsakoff syndrome

It is characterized by signs and symptoms of confusion, ataxia, vision changes, coma due to lack of vitamin B1, often associated with alcoholism.


Treatable Causes of Dementia

Head injury:

This refers to brain damage from accidents, such as motor vehicle wrecks and falls; from assaults, such as gunshot wounds or beatings; or from activities such as boxing without protective gear. The resulting damage of brain cells can lead to dementia.


Infections of brain structures, such as meningitis, bacterial and viral  and encephalitis, can be primary causes of dementia. Other infections, such as HIV/AIDS and syphilis, can affect the brain permanently in later stages. In all infection cases, inflammation in the brain damages cells which leads to memory impairment.

Normal pressure hydrocephalus: as name suggest pressure within CSF is normal but there is hydrocephalus because of decrease absorption of CSF.This condition raises the fluid pressure inside the skull and compresses brain tissue from outside. It may cause severe damage and death. If fluid builds up in the ventricles, the fluid pressure remains normal (“normal pressure hydrocephalus”), but brain tissue is compressed from within.

Simple hydrocephalus:

Simple hydrocephalus may cause typical dementia symptoms or lead to coma. In normal pressure hydrocephalus, people have trouble walking and become incontinent (unable to control urination) at the same time they start to lose mental functions, such as memory. If normal pressure hydrocephalus is diagnosed early, the internal fluid pressure may be decreased by putting in a shunt. This can stop the dementia, the gait problems, and the incontinence from getting worse.

Brain tumors:

Tumors can cause dementia symptoms in a number of ways. A tumor can press on structures within the brain such as the hypothalamus or pituitary gland, which control hormone secretion. They can also press directly on brain cells, damaging them. Treating the tumor, either medically or surgically, can reverse the symptoms in some cases.

Toxic exposure:

People who work around solvents or heavy metal dust and fumes (lead especially) without adequate protective equipment may develop dementia from the damage these substances can cause to brain cells. Some exposures can be treated, and avoiding further exposure can prevent further damage.

Metabolic disorders:

Diseases of the liver, pancreas, or kidneys can lead to dementia by disrupting the balances of salts (for example, sodium and calcium) and other chemicals (like low glucose levels) in the blood. Often, these changes occur rapidly and affect the person’s level of consciousness. This is called delirium. Although the person with delirium, like the person with dementia, cannot think well or remember, treatment of the underlying disease may fully reverse the condition. If the underlying disease persists, however, brain cells may die, and the person will have dementia.

Hormone disorders:

Disorders of hormone-secreting and hormone-regulating organs such as the thyroid gland, the parathyroid glands, the pituitary gland, or the adrenal glands can lead to hormone imbalances, which can cause dementia if not corrected.

Hypoxia brain damage:

People who do not have enough oxygen in their blood may develop dementia because the blood brings oxygen to the brain cells, and brain cells need oxygen to live. The most common causes of hypoxia are lung diseases such as emphysema or pneumonia. These limit oxygen intake or transfer of oxygen from the airways of the lungs to the blood. Cigarette smoking is a frequent cause of emphysema. It can worsen hypoxic brain damage by damaging the lungs and also by increasing the levels of carbon monoxide in the blood. Heart disease leading to congestive heart failure may also lower the amount of oxygen in the blood. Sudden, severe hypoxia may also cause brain damage and symptoms of dementia. Sudden hypoxia may occur if someone is comatose or has to be resuscitated.

Drug reactions, overuse, or abuse:

Some drugs can cause temporary problems with memory and concentration as side effects in elderly people. Misuse of prescription drugs over time, whether intentional or accidental, can cause dementia. The most common culprits are sleeping pills and tranquilizers. Other drugs that cause dry mouth, constipation, and sedation (“anticholinergic side effects”) may cause dementia or dementia symptoms. Illegal drugs, especially cocaine (which affects circulation and may cause small strokes) and heroin (which is very anticholinergic) may also cause dementia, especially in high doses, if taken for long periods, or in older people. The withdrawal of the drug usually reverses the symptoms.

Nutritional deficiencies:

Deficiencies of certain nutrients, especially B vitamins such as low levels of vitamin B12 or B1, can cause dementia if not corrected.

Chronic alcoholism:

Dementia in people with chronic alcoholism is believed to result from other complications such as liver disease and nutritional deficiencies.

Dr. Navin Tiwari

Director, Asian Neuro Centre, Indore and Consulting Neurologist with more than 10 years of experience.



Our Alzheimer and Memory Clinic is a specialist clinic for people with neurological problems resulting in memory loss, confusion, difficulty in speech and understanding, change in personality, aggressive behaviour, hallucinations or depression. The clinic offers a comprehensive screening and care program for AD and other memory disorders, including neurology consultation, physical and cognitive rehabilitation, and psychotherapy. Since cognitive and behavioural problems affect the family along with the patient, we also offer family counselling services, help target rehabilitative goals and equip the family for the supported long term home care.

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