Injury to the left temporal lobe can result in semantic dementia.


Semantic memory involves the knowledge of meanings and relationships between objects, facts, concepts and words in long-term memory.


Semantic dementia is associated with impairment of semantic memory while preserving other cognitive domains.


Features of impaired semantic memory:

(1) anomia (inability to recognize and name objects)

(2) impaired spoken and written verbal comprehension

(3) impairment of general knowledge

(4) difficulty in finding words

(5) fluent aphasia (speech is grammatically correct and well-articulated but lacks content, much like a politician)

(6) associative agnosia (inability to say what something is used for)


If the right temporal lobe is also injured then the patient may experience:

(1) prosopagnosia (inability to recognize and name faces)

(2) prominent social impairment

(3) diminished insight and blunted affect

(4) bizarre behaviors


The remainder of the neurologic exam may be totally normal. The patient may be oriented and able to function fairly well. However, over time the person may gradually deteriorate with increasing impairment.


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