Abstract
The present study aims to restudy the correlation between the internal auditory meatus (IAM), the cochlear nerve canal (CNC), the cochlear nerve (CN) and inner ear malformations. In this retrospective study design, the abnormal diameter of the IAM, CNC and CN in patients with any kind of inner ear malformations was evaluated using multi-slice spiral computed tomography (MSCT) (37 patients) and magnetic resonance imaging (MRI) (18 patients). Of 37 MSCT-diagnosed patients, 2 had IAM atresia, 11 IAM stenosis, 22 enlarged IAM, and 2 normal IAM with an abnormal CN. MRI diagnoses of 18 patients revealed 8 cases of aplastic CN, 6 hypoplastic CN, and 4 normal CN. CNC stenosis was associated with CN hypoplasia (P < 0.001). Patients with absent or stenotic IAM had less CN development than those with normal or enlarged IAM (P = 0.001). We propose a modification of the existing classification systems with a view to distinguishing malformations of the IAM, CNC and CN.
Highlights
The prevalence of congenital sensor neural hearing loss (SNHL) is approximately 1 in every 650 newborns [1]. 50 % of the congenital SNHL cases are caused by environmental exposures during pregnancy, while the other half by genetic mutations [2]
Jackler et al [4] was the first to put forward the classification system, which was later revised by Sennaroglu et al [5] who classified the internal auditory meatus (IAM) malformations as absent, narrow, or enlarged, yet without taking into consideration the presence or absence of the cochlear nerve (CN)
IAM stenosis was observed in 18 ears of 11 patients, and the IAM was absent in 3 ears of 2 patients
Summary
The prevalence of congenital sensor neural hearing loss (SNHL) is approximately 1 in every 650 newborns [1]. 50 % of the congenital SNHL cases are caused by environmental exposures during pregnancy, while the other half by genetic mutations [2]. Jackler et al [4] was the first to put forward the classification system, which was later revised by Sennaroglu et al [5] who classified the internal auditory meatus (IAM) malformations as absent, narrow, or enlarged, yet without taking into consideration the presence or absence of the cochlear nerve (CN). Casselman’s classification system [6] identified two types of IAM stenosis using HRCT and MRI: the absence of the vestibulocochlear nerve and the undeveloped or underdeveloped cochlear branch. His classification system is based solely on IAM stenosis to the exclusion of the cases where the CN is malformed but the IAM is normal or enlarged
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