Language outcomes following long-term auditory processing training in individuals with neurodevelopmental disorders: a retrospective case series.

Background: In this retrospective case series, the longitudinal trajectories of receptive language, expressive language, and vocabulary acquisition during auditory processing training (APT) were described for seven individuals with different neurodevelopmental characteristics. The study aims to highlight intra-case developmental patterns rather than to assess the intervention's effectiveness. Methods: Archived clinical records of seven participants with follow-up periods ranging from 24 to 48 months were reviewed. For all cases, the Preschool Language Scale-4 (PLS-4) scores at the baseline, 6-month, 12-month, 18-month, and 24-month observation windows were retained as unique age ranges corresponding to the highest item group in which all items were correctly completed at each assessment. Where a participant correctly completed all items in one age group but was unable to complete all items in the subsequent age group, their level was classified as the age group in which they had completed all items. Word counts reflect newly recorded words within each interval. The analyses were conducted on a case-by-case and descriptive basis; no inferential statistical tests were used. Results: By the twenty-fourth month, all seven cases had progressed to a higher PLS-4 item group age range compared with baseline, in terms of both receptive and expressive language. The number of newly recorded words in the shared observation window also increased at each stage. Whilst the median number of words recorded at baseline was 4 (range: 0-34), this figure was determined to be 678 (range: 133-1,150) for the 18-24-month period. Excluding initial words, the median total number of new words recorded between 0 and 24 months was 1,126 (range: 288-2,238). Individual developmental trajectories varied considerably. Conclusion: The data indicate that, over the follow-up period, there was progress and an increase in vocabulary acquisition in the age groups corresponding to the PLS-4 item groups at the case level. However, due to the small, clinically heterogeneous sample, the absence of a control group, and concurrent developmental and educational support, the observed changes cannot be causally attributed to APT. The findings are considered to be hypothesis-generating clinical observations for future controlled studies.