Expressive Aphasia involves only an inability in using symbols to express thoughts.
In the Visual modality, a common experience we may have in pulling up concepts is when we are trying to write a paper or a report.
Often we find ourselves sitting for a long period of time looking blankly at the paper, wishing something would come into our mind to write.
When these experiences become the rule (under pathological conditions), rather than the exception, communication becomes a trickle.
Expressive Aphasia is a problem, not in developing ideas, but in finding the symbols to express them.
For the Auditory modality its impact would be an inordinate degree of difficulty in word finding, grammatical formulation, or remembering the pronunciation of words.
In the visual modality, one would likewise have problems in recalling the written word, the written grammar or the way the word was written.