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

The "Near"-Narrowed Internal Auditory Canal Syndrome in Adults: Clinical Aspects, Audio-Vestibular Findings, and Radiological Criteria for Diagnosis

INTRODUCTION

Vestibular Paroxysmia (VP) refers to short attacks of vertigo, spontaneous or triggered by head movements, and implies the presence of a compressive vascular loop in contact with the cochleovestibular nerve (CVN). Classically, a narrowed internal auditory canal (IAC) corresponds to a diameter of less than 2 mm on CT, usually associated with a hypoplastic CVN on MRI. The aim of this study was to discuss a distinct clinical entity mimicking VP in relation to a "near"-narrowed IAC (NNIAC) and to propose radiological criteria for its diagnosis.

METHODS

Radiological measurements of the IAC were compared between three groups: the study group (SG, subjects with a clinical presentation suggestive of VP, but whose MRI of the inner ear and pontocerebellar angle excluded a compressive vascular loop) and two control groups (adult and children) with normal vestibular evaluations and no history of vertigo.

RESULTS

59 subjects (18 M and 41 F) were included in the SG. The main symptoms of NNIAC were positional vertigo, exercise- or rapid head movements-induced vertigo, and dizziness. The statistical analysis in the study group showed that the threshold values for diagnosis were 3.3 mm (in tomodensitometry) and 2.9 mm (in MRI) in coronal sections of IAC. Although a significantly lower mean value for axial IAC diameter was found in SG compared with controls, the statistics did not reveal a threshold due to the large inter-individual variations in IAC measurements in normal subjects. There was no significant difference in IAC diameter between the adult and pediatric controls.

CONCLUSIONS

In the present study, we report a new anatomopathological condition that appears to be responsible for a clinical picture very similar-but not identical-to VP in association with the presence of an NNIAC. The diagnosis requires a careful analysis of the IAC's shape and diameters in both axial and coronal planes.

Facts of Vertigo in Adolescents: Controversies and Challenges – A Narrative Review

Vertigo is a common complaint in the general population affecting 5% of adults in one year. At least 29.5% of adults have referred vertigo during life. Even though the prevalence of vertigo is well known in adults the epidemiologic data in adolescents is sparse. To date, it is known that adolescent females are usually affected by vertigo and some conditions such as depression and anxiety are found in this population. However, the lack of information about the prevalence of most common types of vertigo in adolescents, predisposing factors, challenges, and controversies in clinics in the literature, present a challenge for clinicians regarding the approach and follow-up of this population. Herein, we performed a literature review including data about the prevalence, most common types of vertigo and controversial events in the approach of vertigo in adolescents over the last two decades.

Morphology of the internal auditory canal: Deriving parameters from computer tomography scans. An observational STROBE-MR study

OBJECTIVES

The objective of this study is to identify and define landmarks to adequately describe the internal auditory canal for inclusion in three-dimensional computational models of the cochlea and its surrounding structures.

PARTICIPANTS

Computer tomography scans of live human cochleae were collected in the retrospective period. Descriptive and comparative statistics were used to describe the data obtained from the scans.

RESULTS

The mean anterior-posterior (AP) diameter at the base of the basal turn, the diameter of the AP at the midpoint of the IAC, and the anterior and posterior length of the internal acoustic canal were measured. 57.14% of the internal acoustic canals observed presented with a cylindrical, 40.48% was funnel-shaped and 2.38 % were bud-shaped. A statistically significant differences were found between the diameters of male and female internal acoustic meatus.

CONCLUSIONS

This paper serves as a reference that provides a set of references for the description of the internal acoustic canal for inclusion in three-dimensional computational reconstruction of the cochlea and surrounding structures.

The Narrowed Internal Auditory Canal: A Distinct Etiology of Pediatric Vestibular Paroxysmia

Vestibular paroxysmia (VP) is a disorder encountered in the pediatric population that etiology has been attributed to neurovascular cross-compression syndrome (NVCC). The purpose of this study was to report a new probable pathological condition, the narrowed internal auditory canal (IAC), which appears to be involved in the development of a clinical picture of VP in the pediatric population. A retrospective descriptive comparative study was conducted to compare clinical, electrophysiological, radiological, and therapeutic outcomes in both etiologies. Overall, 16 pediatric patients suffering from VP were included and divided into two groups: patients with narrowed internal auditory (Group 1) were compared to those with NVCC syndrome (Group 2). Patients in both groups were similar in terms of auditory complaints, as well as hearing, vestibular, and electrophysiological status. A narrowed IAC was encountered in the adolescent age category and females, especially those with rapid growth. The diagnosis requires a careful analysis of the shape and diameters of the IAC. Radiologic measurements in the axial plane do not seem to be sufficient to confirm the diagnosis, and, therefore, an analysis of diameters in the coronal plane is required. Treatment with sodium-channel blockers drugs showed promising results not only by relieving vertigo but also by normalizing the electrophysiological findings. In conclusion, a narrowed IAC can be considered in patients suffering from VP.

The influences of porus acusticus internus on ethnicity and importance in preoperative and intraoperative approaches

PURPOSE

The influences of porus acusticus internus (PAI) on ethnicity and differences between populations have not been investigated so far. Therefore, we performed this study to elucidate further the relationship between the different morphologies of PAI and ethnicity and to discuss their effects on surgery.

METHODS

One hundred twenty dry adult human temporal bones (61 male, 59 female) were investigated in the study. Their horizontal diameter (HD), vertical diameter (VD), shape, prevalence of the shapes of PAI, and the distance from the sulcus for the sigmoid sinus (SSS), sulcus for superior petrosal sinus (SSPS), and jugular foramen (JF) of dry Turkish temporal bones were recorded.

RESULTS

Forty-three (35.8%) elliptical (or transverse) and 77 (64.1%) oval (or round) PAI were detected in the Turkish dry temporal bones. On both sides, round PAI were identified more frequently than elliptical ones (32; 26.6% (left); 39; 32.5% (right)) (p < 0.05). There was a similarity between the Indian and Turkish dry temporal bones in terms of distance from the PAI to the SSPS (7-8 mm) and SSS (19-20 mm) (p = 0.01) and prevalence of morphology of PAI (oval and elliptical) (p = 0.04, p < 0.05).

CONCLUSION

The findings of the present study provided a detailed understanding of the preoperative and intraoperative identification of different morphologies of PAI and ethnicity. The ethnicity might contribute to morphology of the PAI and it can be explain the similar forms and distances between the various ethnic populations.