Various Types and Causes of Dementia

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There are several causes of dementia. Some causes are reversible, such as head trauma, certain medications, and metabolic disorders. Other causes are not reversible and knowing which type of dementia a patient has can help hysicians tailor their care appropriately.

1. Alzheimer’s Disease

Alzheimer’s is the leading cause of dementia. It accounts for roughly two-thirds of dementia cases. Alzheimer’s is a progressive disease that is characterized by depositions of proteins in the brain in the form of plaques and tangles.

Scientists are still trying to figure out what causes Alzheimer’s. Advanced age, family history, and lifestyle factors such as smoking seem to influence a person’s risk of developing Alzheimer’s.

2. Vascular Dementia

Vascular dementia is the second most common cause of dementia. It results from reduced blood flow to the brain from either a narrowing or complete blockage of blood vessels that deprives blood cells of vital oxygen and nutrients. Vascular dementia can be caused by multiple small strokes, a single large stroke, diabetes, or hypertension.

Frontotemporal Dementia

Frontotemporal dementia (FTD) is a characterized by atrophy, or wasting away, of the frontal and temporal lobes of the brain in the absence of Alzheimer's. It usually occurs earlier than Alzheimer's disease with onset occurring between 35 to 75 years old. It progresses more rapidly than Alzheimer's and has a shorter life expectancy.

FTD may have a genetic link but scientists are still unsure of the exact cause.

FTD typically presents with behavioral changes, usually as inappropriate social or personal conduct. Problems with speech, called aphasia, is the other main presentation of FTD.

4. Lewy Body Dementia

Lewy body dementia, named for Friederich H.

Lewy, who first described the deposits in the early 1900s, is characterized by deposits of the protein alpha-synuclein inside brain cells. While many symptoms of Lewy Body dementia resemble Alzheimer’s, three symptoms set it apart from other types of dementia: vivid hallucinations, varying levels of consciousness or alertness, and severe sleep disturbances.

5. Parkinson’s Disease

Parkinson’s disease is the progressive deterioration of the nerve cells in the brain that produce the important brain chemical dopamine. Dopamine works as a chemical messenger in the brain, coordinating smooth and balanced muscle movement. Without dopamine, the brain is unable to communicate, leading to a loss of ability to control body movements.

In its advanced stages, Parkinson’s can effect cognitive functioning, leading to difficulty retrieving memories, problems with reasoning, decision making, and problem solving, and depression. Dementia occurs in roughly 20% to 60% of patients with Parkinson’s disease.

6. Huntington’s Disease

Huntington’s disease is an inherited disease that usually occurs in a person’s 30s or 40s.

It is characterized by uncontrolled movements, emotional disturbances and mental deterioration. With Huntington’s disease, progressive mental deterioration with resultant dementia may be the first signs of the disease. Children with one parent who is diagnosed with Huntington’s gene have a 50% chance of developing the disease themselves.

7. HIV/AIDS

HIV/AIDS is a virus that is contracted through contact with an infected person’s blood or body fluids. AIDS related dementia may be related to CD4+ T-cell count nadir and duration of immunosuppression. Before antiretoroviral therapy, AIDS related dementia was linked to a low CD4+ count and high viral loads. Now, with effective antiretroviral therapy which slows the progress of HIV and AIDS, patients are living longer and aren't succumbing to opportunistic infections at the rate they once did. These patients may be at risk for developing AIDS related dementia as they age

Symptoms of AIDS related dementia include symptoms forgetfulness, slowness, difficulties with concentration and problem solving, and hallucinations.

8. Creutzfeldt-Jakob disease (CJD)

Most commonly known as Mad Cow disease, Creutzfeldt-Jakob disease (CJD) is caused by prions. These prions destroy the brains ability to function. CJD may have a genetic link but most cases are sporadic with no known cause. Some cases may be the result of exposure to contaminated medical equipment during procedures. CJD-related dementia often progresses rapidly over several months and involves problems with attention, concentration, appetite, vision and coordination.

Sources:

Vascular dementia. Alzheimer's Association. November 21, 2007.
http://www.alz.org/alzheimers_disease_vascular_dementia.asp.

Gilliland, M. Dementia J Pract Nurs. 2007 Winter;57(4):5-13; quiz 14-6.

Marie-Florence Shadlen, MD and Eric B Larson, MD, MPH. Dementia Syndromes. UpToDate.com

Alexander W Thompson, MD, MBA, Andrew A Pieper, MD, PhD, and Glenn J Treisman, MD, PhD. Dementia and delirium in HIV-infected patients. UpToDate.com.

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