Planning to incorporate cognitive measures in clinical care? - Some theoretical and practical learnings, evaluating 54 studies in a systematic scoping review.

Cochlear implants (CIs) are considered an effective treatment for severe-to-profound sensorineural hearing loss. However, speech perception outcomes are highly variable among adult CI recipients. Top-down neurocognitive factors have been hypothesised to contribute to this variation that is currently only partly explained by biological and audiological factors. Studies investigating this, use varying methods and observe varying outcomes, whose relevance has not been evaluated in a review before. Gathering and structuring this evidence in this scoping review, provides a clear overview of where this research line currently stands, with the aim of guiding future clinical studies and practice.
Objective: To understand to which extent different neurocognitive factors influence speech perception in adult CI users with a postlingual onset of hearing loss, by systematically reviewing the literature.
Methods: A systematic scoping review was performed according to the PRISMA guidelines. Studies investigating the influence of one or more neurocognitive factors on speech perception post-implantation were included. Word and sentence perception in quiet and noise were included as speech perception outcome metrics and six key neurocognitive domains as defined by the DSM-5, were covered during the literature search. (Registered: 10.17605/OSF.IO/Z3G7W, last search April 2022).
Results: From 5668 retrieved articles 54 articles were included and grouped into three categories: 1) Nineteen studies investigating brain activation, 2) Thirty-one investigating performance on cognitive tests, and 3) Eighteen investigating linguistic skills.
Conclusion: The use of cognitive functions, recruiting the frontal cortex, the use of visual cues, recruiting the occipital cortex, and the temporal cortex still available for language processing, are beneficial for adult CI users. Cognitive assessments indicate that performance on nonverbal intelligence tasks positively correlated with speech perception outcomes. Performance on auditory or visual working memory, learning, memory and vocabulary tasks were unrelated to speech perception outcomes and performance on the Stroop task not to word perception in quiet. However, there are still many uncertainties regarding the explanation of inconsistent results between papers and more comprehensive studies are needed. The evaluation of the included studies has led to several recommendations for future clinical studies (applicable to both the adult and pediatric population), which will be the focus of the presentation.