Nontumorous Enlargement of the Internal Auditory Canal: A Risk Factor for Sensorineural Hearing Loss? A High Resolution CT-Study

Abstract

Purpose: First aim of the study was to define normal shape and diameter of the internal auditory canal (IAC). In the second part the clinical relevance of IAC-enlargement was analyzed, considering also lesions of the subtle structures at the fundus of the internal auditory canal. Materials and Methods: 440 high resolution CT-scans of the temporal bone were used for retrospective analysis of the internal auditory canal and its fundus region. Results: The mean value of the IAC diameter in axial and coronal plane was determined. In 20 of 440 patients IAC enlargement was found. In the group with pronounced enlargement (3fold SD) nearly all patients suffered from hearing impairment. In some of them we found structural abnormalities near the IAC fundus in the CSF/perilymph border zone. Conclusion: A new CT-based definition of normal shape and diameter of the internal auditory canal is presented. There is some evidence that a pathologic transmission of CSF-pressure in case of IAC-enlargement and/or abnormal fistulous communications could play an important role in the pathophysilogy of hearing loss. Key points: ??New CT-based definition of normal internal auditory canal. ??Nearly all patients showing pronounced IAC-enlargement suffer from hearing impairment. ??Possible pathomechanism: Transmission of CSF-pressure on the inner ear. Citation Format: ??Stimmer H, Niedermeyer HP, Kehl V et?al. Nontumorous Enlargement of the Internal Auditory Canal: A Risk Factor for Sensorineural Hearing Loss? A High Resolution CT-Study. Fortschr R?ntgenstr 2015; 187: 450???458

Enlarged vestibular aqueducts and other inner-ear abnormalities in patients with Down syndrome

“…In particular, prior studies have demonstrated decreases in internal auditory canal and vestibule size in individuals with Down syndrome, as compared to normal subjects 16 , 23 and normative data 22 . However, we report increases in internal auditory canal and vestibule size among our study group, as determined by comparisons to previously established normative data 27 28 Previous studies have demonstrated relationships between both narrow 23 and dilated 29 , 30 internal auditory canal widths and sensorineural hearing loss.…”

“…Normative data from Stimmer et al . were used as a reference for determinations in internal auditory canal width, with measurements greater than 7.8 mm on the right and 7.7 mm on the left in the axial plane signifying dilation 27 . Vestibule widths were assessed based on normative data established by Purcell et al 28 …”

Deep phenotyping of the neuroimaging and skeletal features in KBG syndrome: a study of 53 patients and review of the literature

“…Nevertheless, IAC evaluation may be considered during the follow-up of individuals with KBG syndrome and hearing defects, since patulous IAC was proposed as a risk of complications during ear surgery. 34 …”

“…Nevertheless, IAC evaluation may be considered during the follow-up of individuals with KBG syndrome and hearing defects, since patulous IAC was proposed as a risk of complications during ear surgery. 34 Additional novel findings included partial agenesis of septum pellucidum (figure 1K), dilation of Meckel's cave, persistent hyperplastic primary vitreous (figure 1L), and hypoplasia of olfactory bulb and olfactory nerve. Interestingly, it has been suggested that Ankrd11-deficient mice may show defects in olfactory bulb development (A. Voronova, personal communication at KBG Scientific Meeting, 7 June 2022).…”

A Pilot Study to Investigate the Relationship Between Interaural Differences in Temporal Bone Anatomy and Normal Variations in Caloric Asymmetry

“…DICOM images for each head CT scan were imported into image analysis software Avizo 8.1 standard (FEI Visualization Sciences Group, Burlington, MA) and deidentified. Moreover, 3D reconstructions of the temporal bone anatomy were created in Avizo, and the following parameters were computed: mastoid airspace and bone volume (V), mastoid airspace and bone surface area (SA), and mastoid airspace and bone surface-area-to-volume ratio (SA:V); lateral semicircular canal (LSCC) V, LSCC SA, LSCC SA:V, and LSCC-to-TM distance; and internal auditory canal (IAC) diameter and circumference using two separate protocols for IAC measurement (Proctor, 1982;Stimmer, Niedermeyer, Kehl, & Rummeny, 2015). This process is visually depicted in Figure 2.…”