Prognostication is a central part of paediatric cochlear implantation (PCI). Accuracy is essential to counsel the family with respect to the likely outcome; such counselling is the key to a truly successful outcome, where the results equal or exceed expectations. The overarching aim of this research was to evaluate, identify and refine the elements of the PCI prognostication process. For this purpose, several objectives were pursued: an exacting evaluation of prior literature; definition and evaluation of the concept of “success” in PCI with suggested improved methodology to achieve this end; analysis of PCI professionals’ concepts of success in PCI; examination of local experiences in PCI to confirm validated prognostic threats and emerging threats in PCI; examination of the role of the auditory cortex as the main influence on prognostication, with an analysis of the influences that determine its function; and, development of more structured and effective PCI prognostication, utilising an index of possible factors that might be used to guide future PCI processes. Therefore, the aim of this research was to advance the process of prognostication in PCI.
To pursue this end a series of five studies was conducted. Study 1 examined the research in the literature that dealt with PCI via a systematic literature review. This review found that from a considerable body of evidence relevant to prognostication there is a relative paucity of well-constructed (case control) studies extant in the literature. Only four factors seemed satisfactorily examined in depth: late age at implantation, inner ear malformations, and meningitis were associated with poorer outcomes and Connexin 26 (GJB2 mutations) did not influence outcomes.
Accurate prognostication has the ability to enhance the success of the PCI process but as yet, a valid method of measuring this “success” remains to be formulated. Study 2, therefore sought to investigate and develop a method for defining and evaluating success in PCI using a pilot caseload of 25 children. It is argued that success in PCI is achieved when the outcome matches or exceeds the preoperative expectations of the well-counselled family. Accurate prognostication was seen in 14 cases, 5 had better outcomes than expected and 6 obtained poorer results. Poor general medical condition and adverse family situations were commonly associated with poorer outcomes. The assessment process used in this study appeared to be practical and accurate, however, further research is required to develop this approach further.
To expand upon the concept of “success” in PCI, a survey was conducted in Study 3 to identify professionals’ perceptions of factors that underlie successful outcomes in PCI, and to elicit potential areas requiring further scrutiny. It was considered that PCI professionals are in a unique position to provide insight in this area because of their long-term role in the care of children with cochlear implants (CIs). A multidimensional survey based on factors in the clinical pathway to success in PCI was developed and used to examine aspects perceived to contribute to a successful outcome. A total of 55 PCI professionals (10 surgeons, 22 audiologists, 1 psychologist, 15 speech pathologists, 3 social workers, 4 teachers of the deaf) responded. The perspectives provided by those surveyed suggest that they view success as maximising the potential of the child in the areas of age-appropriate listening and spoken language, addressing realistic preoperative goals and expectations, and achieving device wearing and attendance compliance. The important role parents play in successful outcomes was also highlighted, as was the need for future collaborative work to develop and validate robust and reliable outcome measures for monitoring and evaluating children with CIs, particularly those with additional disabilities.
To further explore the spectrum of prognostic factors that may influence successful outcomes in PCI, a retrospective chart review of 174 children, implanted between 1995 and 2008 with a unilateral multichannel CI, was undertaken in Study 4. The primary aim of this study was to investigate factors that significantly influence PCI outcomes including any emerging phenomena. Factors that were significantly associated with poorer speech and language outcomes were inner ear malformations and problematic family environments. Later age at implantation was marginally related to poorer outcomes; however the inclusion of those with congenital, acquired and progressive losses in the study sample may have influenced the result. The significance of family functioning for successful outcomes in PCI is an under-researched area and this study identified the importance of an intact family to maximise the overall success for an individual child.
During the retrospective chart review in Study 4 it became evident that prior studies lacked focus on the critical pathological processes that affected PCI and its prognostication. Therefore, Study 5 expanded upon the findings of Study 4 and examined the role of the auditory cortex in PCI prognostication. The 174 children from the previous study were further examined and cases were divided into common aetiological groups, according to the main cause of deafness. Threats to cortical function were examined and classified as primary (direct action on the structure or function of the cortex), secondary (interruption of auditory flow from the CI to the cortex) or, tertiary (denial of stimulation from the CI). To illustrate the relevance of these threats, this work explored the relationship of the aetiology of deafness to the preoperative auditory pathway pathology, and then the site and action of the phenomena that caused poorer PCI outcomes. Frequently, case aetiology did not indicate the true case pathology and it was evident that the site, nature, severity and action of adverse influences were critical. Particularly, prior common research descriptors (e.g., “meningitis") poorly described cortical function. PCI prognostication therefore, requires a detailed evaluation of the auditory cortex status and also any potential risks to its function or auditory input.
Chapter 7 addressed the ultimate aim of this study which was to develop an evidence-based prototype cochlear implant paediatric prognostic index (CIPPI) as an aid for future PCI team guidance. This biopsychosocial index combines the most common variables and current knowledge of prognostic factors in PCI. It requires validation, adjustment and further research and development, however, it has the potential to enhance the prognostication process in PCI. The underlying assumption is that if the probabilities of the impact of prognostic factors can be estimated as accurately as possible, then this will enhance clinical decision-making and consequently child outcomes.
In summary, prognostication in PCI is a complex area that requires ongoing scrutiny and is a work in progress. The research findings in this thesis have implications for the PCI team’s ability to provide evidence-based decisions and recommendations for surgical intervention and, ultimately, improve the success of the procedure.