Pure word deafness is a rare type of aphasia that results from damage to language-specific auditory areas of the brain. People with this disorder feel as though they can't hear when someone else is speaking, even if the person speaking is doing so in a loud voice. However, they have no trouble hearing other sounds, such as a telephone ringing or a door bell. People with pure word deafness also have an inability to write if they are asked to do so, but they are able to write spontaneously.
Sometimes pure word deafness is the final result of a Wernicke's aphasia which improved. In fact, the only clear difference between pure word deafness and Wernicke's aphasia is that while people with Wernicke's aphasia lose the ability to write comprehensible sentences, people with pure word deafness maintain the ability to write.
When pure word deafness is due to a stroke, it results from damage to both the nerve fibers that connect the part of the brain that processes hearing (primary auditory cortex) and the part of the brain that processes language (the association areas of the superior temporal lobe). Most cases of pure word deafness involve damage to these areas in both sides of the brain.
Source:
Allan Roper and Robert Brown, Adam's and Victor's Principles of Neurology, eight edition 2005, pp 417-430.
