Auditory verbal agnosia

Auditory verbal agnosia (AVA), also known as pure word deafness, is the inability to comprehend speech. Individuals with this disorder lose the ability to understand language, repeat words, and write from dictation. However, spontaneous speaking, reading, and writing are preserved. Individuals who exhibit pure word deafness are also still able to recognize non-verbal sounds. Sometimes, this agnosia is preceded by cortical deafness; however, this is not always the case. Researchers have documented that in most patients exhibiting auditory verbal agnosia, the discrimination of consonants is more difficult than that of vowels, but as with most neurological disorders, there is variation among patients.

Auditory verbal agnosia can be referred to as a pure aphasia because it has a high degree of specificity. Despite an inability to comprehend speech, patients with auditory verbal agnosia typically retain the ability to hear, speak, read and write. This specificity suggests that there is a separation between speech perception, non-speech auditory processing, and central language processing. In support of this theory, there are cases in which speech and non-speech processing impairments have responded differentially to treatment. For example, some therapies have improved writing comprehension in patients over time, while speech remained critically impaired in those same patients.

The term "pure word deafness" is something of a misnomer. By definition, individuals with pure word deafness are not deaf – in the absence of other impairments, these individuals have normal hearing for all sounds, including speech. The term "deafness" originates from the fact that individuals with AVA are unable to comprehend speech that they hear. The term "pure word" refers to the fact that comprehension of verbal information is selectively impaired in AVA. For this reason, AVA is distinct from other auditory agnosias in which the recognition of nonspeech sounds is impaired. Classical (or pure) auditory agnosia is an inability to process environmental sounds. Interpretive or receptive agnosia (amusia) is an inability to understand music.

In order to diagnose AVA, two intact abilities need to be established:

If both of these criteria are met and lack of auditory verbal comprehension is apparent, a diagnosis of AVA may follow.

Auditory verbal agnosia is rarely diagnosed in its pure form. Auditory verbal agnosia can both present as the result of acute damage or as chronic, progressive degeneration over time. Cases have been documented that result from severe acute head trauma resulting in bilateral temporal lobe damage. In contrast, auditory verbal agnosia has also been documented to present progressively over several years. In one such case, the patient exhibited progressive word deafness over a 9-year period but did not exhibit any other cognitive of mental deterioration. MRIs showed cortical atrophy in the left superior temporal lobe region.

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