Semantic dementia
In patients with the temporal lobe form of Frontotemporal Dementia, the initial symptom is usually a decline in language abilities. The left temporal lobe is critical for the fluent production of words and especially for assigning meaning to words. Because the language disorder associated with temporal lobe pathology reflects a breakdown in the meaning (or semantic) system underlying language, we prefer the term semantic dementia which conveys the core deficit and progressive nature of the disorder.
Patients typically complain of a “loss of memory for words” involving, at first, less common words and particularly the names of peoples’. As the disease progresses impairment of word comprehension is noticeable which again affects less common words. Reading and spelling are also typically affected, although numerical abilities can be remarkably well spared.
If the right temporal lobe is involved then patients (or carers) often notice problems recognising previously familiar people. It is not uncommon for patients to talk to people as if they were strangers only to discover later that were old friends.
Day-to-day memory is relatively spared but may appear poor due to difficulty with expression. In later stages, the disease spreads to the frontal lobes so that many of the features listed above, especially the changes in emotional responses, empathy and food preference. We have noticed that many patients with semantic dementia are extremely good at puzzles, bingo and jigsaws, and retain sporting abilities such as bowls or golf until very late in their illness.
Skills associated with posterior brain regions such as navigation, route finding and eye-hand coordination are spared at least until very late in the disease.
