İç Kulak Malformasyonlu Hastalarda Anteroposterior Grafi ile Açısal İnsersiyon Derinliği Ölçümü, Koklea Boyutları ve Elektrod Uzunluğu ile İlişkisinin İncelenmesi

Abstract

In 1983 cochlear implantation surgery was performed for the first time in a patient with inner ear anomaly, since then inner ear malformations are no longer contraindication to cochlear implantation. The audiological results of cochlear implantation surgery are affected by several biographical, audiological, cognitive and electrode-related parameters. Angular insertion depth (AID), one of the electrode-dependent parameters, and its relationship with audiological results are popular topics in recent years. Anteroposterior skull X-ray has important advantages such as low radiation exposure, short exposure time, ease of application and interpretation in angular insertion depth measurement. When we look at the literature, there are many studies examining the relationship between angular insertion depth, cochleal dimensions and electrode length in cochleas with normal anatomy. However, studies on parameters affecting angular insertion depth in inner ear malformations are very limited. In our study, it was aimed to determine the reliability of AP X-ray in AID measurement, to give descriptive information about the insertion angles of different electrodes used in inner ear malformations, and to examine the parameters affecting the insertion angle. It is thought that it will guide clinicians in the selection of cochlear implant electrodes. Our study included 198 IEM’s (26 incomplete partition type I (IP-I), 79 IP-II, 9 IP-III, 17 cochlear hypoplasia type II (CH-II), 28 CH-III, 6 CH-IV, 15 cochlear aperture stenosis (CAS), 13 enlarged vestibular aqueduct (LVA), and 5 isolated vestibular dilatation (VD) and 60 healthy cochleas. Basal turn length of the cochlea was measured in axial and coronal oblique reformat sections on high-resolution CT imaging. In post-operative anteroposterior head radiographs, angular insertion depth was measured separately by 3 different clinicians and the results were compared. A very high level of consistency was found in the inter-rater reliability (ICC) test in the measurement of angular insertion depth in the AP head x-ray (R=0.906). AP X-ray seems to be a reliable and easy-to-learn method for measuring angular insertion depth. In the control and study groups, there was a negative correlation between the angular insertion depth and the basal turn length of the cochlea, and a positive correlation between the electrode length and angular insertion depth. (R=0.947 and R=0.606). In incomplete partition type I and II malformations, Med-El Form24 electrode rotated more than 1 turn, Form19 electrode turned less than 1 turn. Choosing a Form24 electrode in IP-I and IP-II cases with gusher will not only provide adequate cochlear stimulation, but will also be beneficial in controlling CSF leakage. In IP-I and IP-II cases where gusher does not develop, long electrodes that better stimulate the cochlea should be selected. In IP-III malformation, both Med-El Form19 and Form24 electrodes rotated more than 1 turn. In IP-III cases where gusher is almost always expected, Form 19 should be chosen for small cochleas and Form 24 for cochleas close to normal in size. Med-El Form19 and Form24 electrodes rotated more than 1 full turn in cochlear hypoplasia. It is appropriate to choose Med-El Form19 and Form24 electrodes according to the cochlea size in cases where gusher develops in cochlear hypoplasias. In cases where gusher does not develop, electrodes with different lengths that will not cause intracochlear damage and provide sufficient cochlear stimulation can be selected. For example, the desired insertion angle can be obtained by completing the insertion at a point between the two indicators (pointing 20 and 25 mm) of the Cochlear Slim Straight electrode, which has an average length between the lateral wall electrodes. Since gusher is not expected in LVA, CAS and isolated VD malformations with normal cochlear sizes, it seems reasonable to use electrodes long enough to provide adequate cochlear stimulation. If the ideal angular insertion depth can be determined to obtain optimal audiological results in inner ear malformations in future studies, the data of this study will help clinicians in electrode selection.