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

Eugen C Ionescu; Pierre Reynard; Samar A Idriss; Aicha Ltaief-Boudriga; Charles-Alexandre Joly; Hung Thai-Van

doi:10.3390/jcm12247580

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

J Clin Med. 2023 Dec 8;12(24):7580. doi: 10.3390/jcm12247580.

Authors

Eugen C Ionescu^{1

2}, Pierre Reynard^{1

2

3}, Samar A Idriss^{1

4

5}, Aicha Ltaief-Boudriga⁶, Charles-Alexandre Joly^{1

2}, Hung Thai-Van^{1

2

3}

Affiliations

¹ Department of Audiology and Neurotology, Civil Hospitals of Lyon, 69003 Lyon, France.
² Team Clinical and Translational Exploration of Sensorineural Hearing Loss, Hearing Institute, Research Center of Pasteur Institute, Inserm U1120, 75015 Paris, France.
³ Department of Physiology, Claude Bernard University, 69003 Lyon, France.
⁴ Department of Otolaryngology, Dar Al Shifa Hospital, Hawally 13034, Kuwait.
⁵ Department of Otolaryngology and Head and Neck Surgery, Eye and Ear Hospital, Holy Spirit University of Kaslik, Beirut 1201, Lebanon.
⁶ Department of Radiology, Civil Hospitals of Lyon, 69003 Lyon, France.

Abstract

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.

Keywords: cross compression syndrome; narrowed internal auditory canal syndrome; sodium channel blockers; vestibular paroxysmia.

Grants and funding

This research received no external funding.