Semantic dementia

The pace of the symptoms and length of disease can vary dramatically from person to person. In general, each type of FTD follows a pattern where the symptoms seen in the mild stage become more pronounced and disabling over a course of 8-10 years.

Mild SD

People with early semantic dementia that is predominantly on the left side of the brain, usually complain of a hard time coming up with the word or name for something. Words that the person uses a lot may remain available, but more unusual words may be replaced by "thingy" or "you know." The tone, rhythm and fluctuations of pitch (prosody) generally sound normal. Memory for day-to-day events is usually spared.

The early signs of SD in people with asymmetric right-sided damage include a decline in empathy or awareness of other people's emotions. 

Moderate SD

After two to three years, the people with left sided damage and those with right sided damage tend to look more similar, as the disease typically progresses to involve both sides. With moderate SD, most people show at least some of the behavioral problems that are similar to the behavioral variant of FTD.

People with moderate semantic dementia will have immense trouble understanding you. They may also have increasing difficulty recognizing the names and faces of people – even friends and family. Reading and writing, mostly likely, will have declined noticeably. The person may still be able to use numbers, colors and shapes – the brain functions responsible for these skills are organized in a different area of the brain from words.

Severe SD

After four to five years of SD, the disease is usually quite advanced, which means the person's language skills have significantly eroded, making communication very difficult while the behavioral problems have significantly increased. Typical behaviors seen in late stage SD include disinhibition, apathy, compulsions, impaired face recognition, altered food preference and weight gain. People with left-sided damage tend to show more interest in visual or non-verbal things while people with right-sided damage tend to prefer games with words and symbols. The time from diagnosis to the end typically takes about six years, although this can vary significantly from person to person.