Background: Word deafness refers to an inability to understand spoken words despite intact hearing. In a cognitive approach, word deafness could be explained by a deficiency at the lower perceptive level of the auditory process. The impairment of the auditory analysis system would explain a disorder of identification of speech sounds. Only few studies addressed rehabilitation of central auditory processing and have described therapy focused on phoneme discrimination.
Objective: To determine whether a specific auditory analysis rehabilitation addressing phoneme discrimination and phoneme recognition may improve oral comprehension and communication.
Method: A single-case experimental design was used in a 65 year-old woman, with word deafness consecutive to a cerebral infarction which occurred 10 months before. Verbal naming, written expression and written comprehension were normal. Verbal comprehension, repetition and phoneme discrimination and recognition were impaired. In terms of cognitive model of auditory processing, the patient showed impairment of the auditory analysis system affecting verbal comprehension. A computerized rehabilitation of auditory analysis system was carried out in two consecutive tasks: phoneme discrimination and phoneme recognition. Errorless learning therapy was used, with a difficulty hierarchy practised from the easier to the most difficult phoneme and systematic visual cues which were progressively delayed and suppressed. This study tested the efficacy and the specificity of this therapy on the addressed tasks (phoneme discrimination and recognition), related tasks (oral comprehension and repetition), independent tasks (recognition of environmental sounds) and daily life (questionnaire).
Results: The phoneme discrimination and recognition impairment was stable over 4 months before therapy. After therapy, phoneme discrimination (p < 0.001) and phoneme recognition (p < 0.0001) were improved. The improvement was specific to verbal sounds recognition, while non-verbal sounds recognition was unchanged. An improvement occurred for repetition (p < 0.05) and oral comprehension (p < 0.01). The communication disability decreased (p < 0.05).
Conclusion: In a case of word deafness, this study demonstrates not only the efficacy of a specific phoneme processing therapy but also its efficacy in the improvement of higher level of cognitive treatment such as oral comprehension and its transfer in daily life. The role of errorless therapy using systematic visual cues and difficulty hierarchy must be underlined.