Semantic Dementia: Symptoms, Causes, And Outlook

Semantic dementia (SD) is a type of frontotemporal dementia (FTD). FTD occurs when there is damage to the neurons in the brain’s frontal and temporal lobes.

FTD is more rare than other forms of dementia and affects people at a younger age. Around 60% of those with FTD are 45 to 64 years old.

This article outlines the symptoms, stages, and causes of SD. It also discusses the difference between SD and Alzheimer’s disease and considers the treatment and outlook for SD.

SD affects semantic memory, a type of long-term memory that stores general knowledge, facts, and concepts. Because these are vital for language comprehension, SD is primarily a language impairment.

SD symptoms generally include:

• anomia, which is the inability to name or describe everyday objects or find the right words during conversation
• difficulty understanding word meanings
• difficulty understanding other people’s speech
• difficulties with reading comprehension and spelling

Symptoms of SD may differ according to the stage of the disease.

This is the earliest stage of SD, when people may have difficulty finding appropriate words and naming objects. During this stage, they may frequently use filler words, such as “thing” or “you know.”

This stage typically occurs 2 to 3 years after the onset of SD. People at this stage may have difficulties understanding others or recognizing familiar names and faces. They may also show impairments in reading and spelling.

This is the final stage of SD, which usually occurs around 6 to 8 years after diagnosis. There may be severe impairments in communication skills and considerable changes in behavior. Symptoms specific to this stage include:

• an inability to recognize faces
• lethargy
• cravings
• a loss of appetite
• weight loss

In most people with SD, the cause is unknown. However, it appears to run in families, and certain genetic variants may play a role.

People with SD have damage to the neurons in the brain’s temporal lobe. Experts think the damage is due to a buildup of a protein called TDP-43 in the brain. People with SD may have specific changes in genes that cause the production of atypical amounts of protein, leading to changes in the brain.

Researchers have suggested that the following genes may contribute to SD when they mutate:

• the tau or MAPT gene
• the GRN gene
• the C9ORF72 gene

SD is the easiest FTD to identify using structural brain imaging techniques, such as functional magnetic resonance imaging (fMRI).

In SD, fMRI images show significant atrophy, or wasting away, of one side of the brain, usually the left. This atrophy is more noticeable in the early stages of the disease because the rest of the brain appears unaffected.

Radiographers may also notice changes to the brain’s white matter, which consists of nerve fibers that allow information exchange between different brain areas.

In the later stages of SD, brain atrophy and changes to white matter are more pronounced.

Learn about the brain’s anatomy.

Alzheimer’s disease (AD) is the most common form of dementia and involves parts of the brain that control thoughts, memory, and language.

• memory loss that disrupts daily life, such as getting lost in familiar places or misplacing objects
• difficulty completing familiar tasks
• difficulty handling money and paying bills
• problems with decision making and judgment
• changes in mood, personality, or behavior

Learn more about Alzheimer’s disease.

SD is progressive, meaning a person will gradually decline and not recover from it.

According to a 2018 review:

• SD typically progresses from mild to moderate disease in 2 to 3 years.
• The time between receiving a diagnosis and developing severe disease is usually around 6 to 8 years.
• Severe SD is the final stage and results in death.

The course of SD varies, and some people die just a few years after diagnosis, while some live more than 10 years.

SD can be challenging for the person with the condition and those around them. To help someone with SD, a person can try the following:

• labeling objects around the home to help reduce episodes of anomia
• speaking slowly and clearly and using short sentences
• giving individuals time to respond
• avoiding interrupting or correcting the person
• acknowledging what the person has said, even if it seems out of context
• rephrasing questions to help the person understand better
• being fully attentive to the person when they are speaking
• minimizing distractions that may interfere with communication, such as a loud television
• maintaining a positive, calm, and friendly tone of voice
• encouraging the person to join in conversations where possible

Anyone experiencing dementia symptoms must consult a doctor as soon as possible to determine the cause. Early treatment can help slow the progression of the disease.

General signs and symptoms to look out for include:

• memory loss
• judgment issues
• impulsive behavior
• confusion
• a loss of interest in everyday activities
• getting lost in familiar surroundings
• difficulty handling money and paying bills
• experiencing hallucinations, delusions, or paranoia
• problems with balance and movement

Semantic dementia (SD) causes language impairments, such as difficulties finding words, understanding word meanings, and understanding speech or written text.

SD occurs due to neuronal changes in the brain’s temporal lobes. Neurons become damaged when there is a buildup of a protein called TDP-43.

To treat SD, doctors may recommend medications for dementia, lifestyle changes, and being physically active.

Early dementia treatment can help slow its progression and improve a person’s quality of life. If someone experiences dementia symptoms, they can speak with a doctor for diagnosis and advice.