Irreversible Dementias - Is It Alzheimers Or Another Dementia: Alzheimers

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Irreversible dementias

Although there are many causes of irreversible dementia, the following conditions are among the most common. In some cases, prompt treatment can prevent further damage, but lost cognitive functioning cannot be restored.

Vascular cognitive impairment

This condition, also known as multi-infarct dementia and vascular dementia, is caused by multiple infarcts, sections of tissue — in this case, brain tissue — that have died because blood circulation is cut off. The decrease in blood flow is often due to atherosclerosis, the accumulation of fatty deposits on artery walls. Multi-infarcts essentially result from a series of many tiny strokes. Each stroke affects such a small area of the brain that at first there aren't any noticeable symptoms. Eventually, though, they can damage a substantial area of the brain, causing many symptoms (see Figure 6).

People with multi-infarct dementia usually have hypertension (high blood pressure), cardiovascular disease, diabetes, or a history of stroke. The classic symptom of multi-infarct dementia is an abrupt mental change, sometimes accompanied by paralysis or slurred speech. The mental deterioration proceeds in a "stairstep" pattern — a person suffers a sudden cognitive decline, the decline levels off, and then new infarcts cause another sudden decline.

Figure 6: Cumulative damage from tiny strokes Multi-infarcts, areas of dead tissue caused by a series of tiny strokes, can cause irreversible dementia. Often, each tiny stroke goes unnoticed because it damages just a small part of the brain and doesn't cause any long-term impairment. While each individual stroke may not be apparent, the cumulative damage is. Once enough of the strokes occur, a significant portion of the brain is damaged and symptoms such as confusion, impairment in thinking, slurred speech, and paralysis may arise.

Degenerative diseases

Most dementias are caused by degenerative diseases, conditions whose deterioration cannot be stopped. Alzheimer's disease is the degenerative disease that is most often responsible for dementia, causing more than 50% of cases. Frontotemporal lobar degeneration, Parkinson's disease, and Huntington's disease account for approximately 25% of all dementias.

Frontotemporal lobar degeneration. This group of diseases, formerly called Pick's disease, is characterized by atrophy of the front part of the brain, including the frontal and temporal lobes. It is a rare condition that is often confused with Alzheimer's disease because the symptoms are sometimes identical.

In cases of frontotemporal lobar degeneration, people exhibit symptoms such as prominent aphasia early in the illness; loss of inhibition, resulting in sociopathic or hypersexual behavior; loss of emotional responses such as fear; and compulsively putting objects in their mouths. The cause of frontotemporal lobar degeneration is unknown, but some variants can run in families, and it is sometimes associated with mutations in a particular gene.

Parkinson's disease. This is a movement disorder resulting from a deficiency of dopamine, a neurotransmitter involved in coordinating muscle activity as well as memory function. Its hallmarks include tremors, rigid limbs, and difficulty starting or stopping movement. Mild cognitive problems are common early in the disease, and dementia occurs in 30%–80% of Parkinson's patients in the late stages.

Some people with Parkinson's disease develop dementia because they also have Alzheimer's disease. In other cases, the dementia is associated with hallucinations and appears to be linked to damage in the limbic and cortical areas of the brain. This variant of Parkinson's is called Lewy body dementia. Drugs that increase dopamine transmission, such as levodopa (Sinemet), help control the physical symptoms of Parkinson's but don't improve mental function.

Huntington's disease. Huntington's disease is a rare inherited disorder linked to an abnormal gene on chromosome 4. Its symptoms include involuntary writhing movements and dementia, and they often begin between the ages of 20 and 40. Mental disturbances may occur before or after physical problems appear, and people are often difficult to care for because of their irritability, aggressiveness, and erratic behavior. Medications can control the movement and mood disorders, but they don't stop the disease from progressing.

Infectious dementias

Virtually any infectious agent that attacks the central nervous system can cause dementia.

Creutzfeldt-Jakob disease. This is a rare, rapidly progressive dementia caused by a type of infectious agent called a prion. The initial symptoms are fatigue and subtle changes in behavior. Typically, the disease progresses to movement problems, seizures, coma, and — within a year — death.

AIDS dementia. This form of dementia occurs in people with AIDS, caused by infection with the human immunodeficiency virus (HIV). The dementia can develop rapidly, sometimes in a matter of weeks, and consists of forgetfulness, inattentiveness, and thinking difficulties.

Neurosyphilis. Before the introduction of penicillin, up to 30% of dementia patients admitted to mental institutions had neurosyphilis. This disorder, which develops about 15 years after syphilis infection, is now rare.

Last updated:	January 23, 2007