الفهرس 
ANATOMY OF THE INNER EAROnly 14 pages are availabe for public view
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Abstract
Radiologic abnormalities of the inner ear are relatively common in children with SNHL, and their identification directly impacts prognosis and management. Therefore, many authors suggest that all children with SNHL undergo radiologic imaging as part of their evaluation.
High-resolution temporal bone computed tomography (CT) has been the first-line imaging study of choice obtained by pediatric otolaryngologists in the workup of children with all types of SNHL.
Nowadays, an increasing proportion of the children scheduled for cochlear implantation have congenital sensorineural hearing loss (SNHL), where 5 to 15% of these cases have malformations of the inner ear (IE)
Clinicians need to classify inner ear malformations in order to correlate certain types with surgical aspects of cochlear implantation and rehabilitation outcomes.
Cochlear implantation is a treatment for patients with severe sensorineural hearing loss/ deafness, who get no help from ordinary hearing aids.
The cochlear implant is surgically placed under the skin near the ear and a very thin electrode array is introduced into the cochlea of the inner ear, where it stimulates the remaining nerve fibers. The operation is complicated; it is performed with the aid of a microscope, and involves drilling very close to vital vessels and important nerves.
High resolution computed tomography (CT) of the temporal bone is a part of the preoperative evaluation preceding cochlear implantation. It is a method for visualizing the bony structures of the middle and inner ear – to diagnose pathology and to describe the anatomy.
The main indication for cochlear implantation is severe-to-profound sensorineural hearing loss that cannot be treated adequately with conventional hearing aids. Many factors are considered when selecting cochlear implant candidates.
First of all, age, emotional and cognitive abilities, cause and duration of deafness, capacity and ability to be retrained and social status should be considered. Secondly, certain anatomical and physiological conditions for proper processing of auditory signals must be met. Decisions on cochlear implant candidacy can be very difficult, particularly regarding children and prelingually deaf adolescents. Over the past few years, pressure has been mounting to lower the minimum age for cochlear implantation in profoundly deaf children in order to improve the outcome. There is evidence that children implanted before 2yrs of age achieve better open-set speech recognition than children implanted later. In recent years, implantation has been performed in children aged between 5 and 11 months. The neural plasticity of the auditory cortex is now widely recognized as an issue. Since hearing in two ears allows people to localize sounds and to hear better in noisy environments, bilateral implants are currently being investigated.
Preoperative imaging will help the clinician identify patients with anatomic contraindications to implantation, but it will also reveal certain anatomical features that have consequences for selecting the specific device and determining which ear to implant. Furthermore, preoperative imaging may also allow the surgical team to anticipate aberrant anatomy and thus reduce the risk of surgical complications. Preoperative imaging ideally addresses several basic anatomical issues. With improvements in high resolution computed tomography (HRCT) and a better understanding of cochlear malformations, the number of reports on the results of cochlear implantation in malformed cochleae has risen steadily in the past decade. Previous criteria for cochlear implantation had excluded children with IE malformations on the assumption that these children would not perform adequately after implantation. Recently published studies, however, report satisfactory hearing results in this group of patients. Their hearing outcomes are similar to those of other profoundly deaf children, with the exception of children with a common cavity type malformation. The variability in performance is considerable, however, especially in patients with severe cochlear malformations.