Morphometric Analysis of the Internal Auditory Canal by Computed Tomography Imaging

Abstract

BackgroundMany clinical and experimental studies have been done to analyze the anatomical and functional aspects of the internal auditory canal (IAC) in human beings since there are great inter-individual variability and structural variations that may occur regarding the other adjacent structures.ObjectivesThe purpose of this study was to characterize the morphology of the internal auditory canal (IAC) during development using high resolution computed tomography (CT) and to analyze its dimensions, which will be determined by measuring the nearby areas and structures using a system of digital image processing.Patients and MethodsCT images of the IAC of 110 normal subjects aged 1 to 92 years (mean age, 46.5 years) of both genders were reviewed to determine the shape, area, opening width (OW), longitudinal length (LL), vertical diameter (VD) and distance from the vestibular aqueduct.ResultsThe shapes observed in children and adults were funnel-shaped (74% and 58.3%, respectively), cylindrical (22% and 30.9%, respectively) and bud-shaped (4% and 10.8%, respectively). The measurements by CT in children were: area= 50.30 mm2, OW = 7.53 mm, length = 11.17 mm, VD = 4.82 mm and the distance between the IAC and the vestibular aqueduct (VA) = 12.63 mm. In adults, the measurements were: area = 44.64 mm2, OW = 7.10 mm, length = 9.84 mm, VD = 4.47 mm and the distance between IAC and VA = 11.17 mm.ConclusionsCT images showed that the IAC has different shapes and when the measurements obtained for children were compared with those of adults, the parameters that presented statistically significant differences in either gender were length and diameter.

The relationship between the dimensions of the internal auditory canal and the anomalies of the vestibulocochlear nerve

“…However, the authors investigated the IAC in individuals aged from 13 to 83 years. Other studies performed on children, like that of Huang et al [10], Lang [12], Li et al [13], and Marques et al [15] classified the normal anteroposterior diameter of the IAC ranging from 3 to 7 mm, from 4.64 to 5 mm, from 2 to 8 mm and stenotic if less than 2 mm, respectively. These variations in considering the normal dimensions could be resulted from the variability in the techniques used in measurements or due to the difference in age groups.…”

“…Several studies examined the dimensions of the internal auditory canal using bony skulls [7], dissected cadavers [20] and radiographs [15]. In the present study, the IAC was considered patulous if its diameter was more than 8 mm and stenotic if less than 3 mm.…”

“…Previous studies classified the normal dimensions of the IAC and its malformations without evaluating the VCN [6,15,21]. Other studies classified the VCN development in only stenotic IAC with the exclusion of normal or enlarged canals [4].…”

“…High resolution computerised tomography (CT) is considered a very sensitive method to investigate the precise dimensions of the IAC and the detection of its anomalies [14][15][16]. Recent technologies in magnetic resonance imaging (MRI) were proved to be more sensitive and specific for diagnosing soft tissue abnormalities in the IAC than the high resolution CT [10,18,25].…”

Anatomy of the fundus of the internal acoustic meatus — micro-computed tomography study

“…Thereby, previous results were limited rather to analysis of the appearance of the entire IAM and not exactly its fundus. For instance, Marques et al [10] has examined the shape of the IAM and established that it could be funnel-shaped (the most common in children and adults), cylindrical or bud-shaped which is the least represented.…”