Frontotemporal dementia

DEFINITION

Frontotemporal dementia (frontotemporal lobar degeneration) is an umbrella term for a diverse group of uncommon disorders that primarily affect the frontal and temporal lobes of the brain — the areas generally associated with personality, behavior and language.

In frontotemporal dementia, portions of these lobes atrophy or shrink. Signs and symptoms vary, depending upon the portion of the brain affected. Some people with frontotemporal dementia undergo dramatic changes in their personality and become socially inappropriate, impulsive or emotionally indifferent, while others lose the ability to use language.

Frontotemporal dementia is often misdiagnosed as a psychiatric problem or as Alzheimer’s disease. But frontotemporal dementia tends to occur at a younger age than does Alzheimer’s disease, generally between the ages of 40 and 75.

CAUSES

In frontotemporal dementia, the frontal and temporal lobes of the brain shrink.

A variety of mutations on several different genes have been linked to specific subtypes of frontotemporal dementia. However, more than half the people who develop frontotemporal dementia have no family history of dementia.

Frontotemporal lobar degeneration is divided into two subtypes, one involving the accumulation in the brain of a protein called tau and one involving the protein TDP-43.

In some cases, the affected parts of the brain contain microscopic abnormal tau protein-filled structures that develop within brain cells (Pick bodies).

Frontotemporal dementia was once known as Pick’s disease, but now that terminology is reserved for the subtype that actually features these abnormal structures.

SYMPTOMS

Identifying precisely which diseases fall into the category of frontotemporal dementia presents a particular challenge to scientists. The signs and symptoms may vary greatly from one individual to the next. Researchers have identified several clusters of symptoms that tend to occur together and are dominant in subgroups of people with the disorder. More than one symptom cluster may be apparent in the same person. The signs and symptoms of frontotemporal dementia progressively worsen with time, almost always over years, eventually requiring 24-hour care.

Behavioral changes

The most common signs and symptoms of frontotemporal dementia involve extreme changes in behavior and personality. These include:

• Increasingly inappropriate actions
• Loss of empathy and other interpersonal skills
• Lack of judgment and inhibition
• Apathy
• Repetitive compulsive behavior
• A decline in personal hygiene
• Changes in eating habits, predominantly overeating
• Lack of awareness of thinking or behavioral changes

Speech and language problems

Some subtypes of frontotemporal dementia are marked by the impairment or loss of speech and language difficulties.

Primary progressive aphasia, one subtype, is characterized by an increasing difficulty in using and understanding written and spoken language. For example, people may have trouble finding the right word to use in speech or naming objects.

People with another subtype, semantic dementia, utter grammatically correct speech that has no relevance to the conversation at hand. They may have difficulty understanding written or spoken language, or they may have difficulty recalling the words for common objects.

People with logopenic phonological aphasia talk slowly and have difficulty finding the right word to use or naming objects. They may have memory difficulties as well.

Movement disorders

Rarer subtypes of frontotemporal dementia are characterized by problems with movement, similar to those associated with Parkinson’s disease or amyotrophic lateral sclerosis.

Movement-related signs and symptoms may include:

• Tremor
• Rigidity
• Muscle spasms
• Poor coordination
• Difficulty swallowing
• Muscle weakness