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, people require 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
• Oral exploration and consumption of inedible objects
• 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.

Two types of primary progressive aphasia are considered frontotemporal dementia. Primary progressive aphasia 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.

Semantic dementia is one type of primary progressive aphasia. It's also known as semantic variant primary progressive aphasia. Individuals with semantic dementia have prominent difficulty naming (anomia) and may replace a specific word with a more general word such as "it" for pen. They may also lose knowledge of word meaning.

Progressive agrammatic (nonfluent) aphasia is another type of primary progressive aphasia characterized by nonfluent and hesitant speech. Speech may sound telegraphic with misuse of pronouns and errors in sentence construction.

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

In frontotemporal dementia, the frontal and temporal lobes of the brain shrink. Usually, the cause is unknown.

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 main 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.

Recently, researchers have confirmed shared genetics and molecular pathways between frontotemporal dementia and amyotrophic lateral sclerosis (ALS). The importance of these connection is currently under investigation.

Your risk of developing frontotemporal dementia is higher if you have a family history of dementia. There are no other known risk factors.