Cochlear implant outcomes and genetic mutations in children with ear and brain anomalies

Introduction. Cochlear implantation (CI) was a significant surgical innovation in the 20th century and represented the first artificial sensory organ that was applied in clinical medicine. Currently, CI is still one of the most effective medical procedures. Nonetheless, cochlear implantation in adults and children represents a controversial issue from an economic, clinical and ethical point of view, especially in specific clinical conditions that could compromise the CI outcome and drastically reduce the chance of an acceptable development of perceptual and linguistic capabilities. These conditions should certainly include the presence of inner ear malformations or brain abnormalities. Objectives. The aims of this work were to study the diagnostic value of high resolution computed tomography (HRCT) and magnetic resonance imaging (MRI) in children with sensorineural hearing loss who were candidates for cochlear implants and to analyse the anatomic abnormalities of the ear and brain in patients who underwent cochlear implantation. We analysed the effects of ear malformations and brain anomalies on the CI outcomes. Finally, we described the genetic mutations that we found in the study group. A control study group of implanted patients without ear and brain anomalies was obtained (virtually) from clinical and literature data for statistical purposes. Materials and methods. The present study is a retrospective observational review of cochlear implant outcomes among hearing-impaired children who presented ear and/or brain anomalies at neuroimaging investigations with MRI and HRCT. Furthermore, genetic results from molecular genetic investigations (GJB2/GJB6 and, additionally, in selected cases, SLC26A4 or mitochondrial-DNA mutations) on this study group were herein described. Longitudinal and cross-sectional analysis was conducted using statistical tests. Results. Between 1 January 1996 and 1 April 2012 at the ENT-Audiology Department of the University Hospital of Ferrara, 620 cochlear implantations were performed. There were 426 implanted children at the time of the present study (who were <18 years). Among these, 143 patients (64 females and 79 males) presented ear and/or brain anomalies/lesions/malformations at neuroimaging investigations with MRI and HRCT. The age of the main study group (143 implanted children) ranged from 9 months and 16 years (average = 4.4; median = 3.0). The most common inner ear malformation is represented by an enlarged vestibular aqueduct; brain lesions are usually represented by white matter disorders. The 35delG in the GJB2 gene remain the most common mutation. Discussion and Conclusions. Good outcomes with cochlear implants are possible in patients who present with inner ear or brain abnormalities, even if central nervous system anomalies represent a negative prognostic factor that is made worse by the concomitant presence of cochlear malformations. Common cavity and stenosis of the internal auditory canal (less than 2 mm) are negative prognostic factors even if brain lesions are absent. Because the cochlear implantation is an invasive and expensive surgical procedure, the identification of predictive factors, even in hearing-impaired patients with cochlear and brain anomalies, is one of the most important goals, because it can help to guide rehabilitation programs that are tailored to meet the expectations of clinicians, teachers and parents. Our findings suggest that cochlear implantation (CI) is a safe and effective procedure even for patients with brain and inner ear abnormalities. Nonetheless, specific conditions, such as a common cavity, or in general, the absence of modiolus and the stenosis of the internal auditory canal, can increase the risk of post-operative complications and prevent the achievement of acceptable perceptual categories. For the aforementioned conditions, it is strictly recommended that cochlear implant indications, neuroimaging and surgery are performed in experienced hospitals.