Less Common Causes of Dementia

Brain tumors can cause dementia if they are located in areas that control thinking or memory. If the tumor cannot be removed surgically and cannot be shrunk by radiation therapy or drugs, it can cause a progressive decline in mental function.

Parkinson's disease results in dementia in some people. This dementia is a mixed dementia with symptoms similar to those of Alzheimer's disease, vascular dementia, and Lewy body dementia. Progressive supranuclear palsy may result in a similar dementia.

In AIDS (usually in the late stages), the human immunodeficiency virus (HIV) may infect the brain. Dementia then develops gradually and progresses steadily, usually over a few months or years. Early, continuing treatment of HIV infection can usually prevent dementia.

Rarely, Lyme disease or syphilis causes dementia. Early treatment of these infections can prevent dementia. Once dementia has developed, treating the infection does not lessen the dementia or restore mental function.

In normal-pressure hydrocephalus, the fluid that normally surrounds the brain (cerebrospinal fluid) is not reabsorbed normally. Fluid accumulates and puts pressure on brain tissue, resulting in dementia. Normal-pressure hydrocephalus also causes urinary incontinence and problems with walking. The feet seem stuck to the floor, so taking a first step is hard. Walking is unsteady. If normal-pressure hydrocephalus is diagnosed early, it can sometimes be treated by draining the excess fluid within the brain through a drainage tube (shunt).

Pick's disease, a rare disease, causes a dementia that resembles Alzheimer's disease. However, the dementia progresses more rapidly. The cause is unknown. People with Pick's disease cannot take the initiative, even to do familiar tasks.

In Creutzfeldt-Jakob disease, also a rare disease, abnormal proteins called prions damage the brain. The resulting dementia progresses rapidly. It often becomes severe and leads to death within a year. A variant of Creutzfeldt-Jakob disease (so-called mad cow disease) is thought to be acquired from eating contaminated beef.

Rarely, chronic subdural hematoma results in dementia. In this disorder, blood accumulates between the outer and middle layers of tissue covering the brain. The blood may put more and more pressure on surrounding brain tissue, progressively impairing mental function. Even soft falls or slight head injuries can cause hematomas, particularly in people who take anticoagulants (which make blood less likely to clot).

Alcohol dementia may result from drinking large amounts of alcohol for many years. Memory is usually affected more than other areas of mental function.