Semantic Dementia by
Dr Rohani Omar, Dr. Jonathan Rohrer & Dr. Jason Warren, Dementia Research Center
SD is caused by degeneration (loss) of brain cells mainly affecting the parts of the brain which are involved in semantic memory (the knowledge of objects, people, concepts and words).
Symptoms
The first symptoms are usually problems with language:
- Difficulty finding the right word (often substituting another word or a general or vague term such as ‘thing’ or instead).
- Loss of knowledge of the meaning of words.
- Speech may still be fluent but the person may talk about things in a vague or ‘roundabout’ manner (circumlocutory speech).
- Difficulty comprehending what other people are saying.
- Difficulty understanding what is read.
- Problems recognising people or everyday items also commonly occur as the disease progresses and may sometimes be the most prominent symptoms.
Other functions such as memory for day-to-day things and calculation are more variably affected and are often normal early in the illness. Behaviour and personality can become affected similarly to frontotemporal dementia (behavioural variant FTLD) as the disease progresses. The course of the disease varies from person to person, however it usually extends over a number of years.
Medical tests
Language ability, memory and other aspects of thinking (cognitive functions) will be assessed, initially by a doctor, and often followed by a more detailed assessment by a psychologist. Brain scans can show the loss of brain cells in semantic dementia, which appears as shrinkage (atrophy) of the affected parts of the brain. It is usually the temporal lobes which are most affected, on the left (language dominant) side more than the right. However, there is no single test that can specifically diagnose semantic dementia with complete reliability during a person’s lifetime. Your doctor will often arrange blood tests or other tests (a brain scan and an EEG or electroencephalogram, and sometimes a lumbar puncture) to help rule out diseases that can produce similar symptoms to SD.
Treatment
There is currently no medication that can cure the disease or slow its progression. Treatment therefore focuses on helping people manage their symptoms, and treating problems such as mood changes that may contribute to the difficulties that people experience.
Prognosis
Problems with language will deteriorate over time. There is a slow but progressive loss of vocabulary and the ability to understand what people are saying. Speech becomes increasingly vague and the quantity of speech tends to diminish. The person may have increasing difficulty recognising familiar people or household items. Changes in personality and behaviour deteriorate. Later in the illness people are likely to have increasing problems carrying out their normal daily living activities and managing their affairs, and they will need extra care and support.
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