Medical Management of the Near-Narrowed Internal Auditory Canal Pathology in the Adult Population: A Preliminary Study

Abstract

Background/Objectives: Objective: To discuss therapeutic outcomes in patients with symptomatic near-narrow internal auditory canal (NNIAC). Methods: We retrospectively analyzed the records of 26 symptomatic patients diagnosed with NNIAC, who had been treated with anti-epileptic drugs. In addition to clinical and radiological data, we recorded I-III latencies of auditory brainstem responses prior to and after medical therapy. Results: Among a total of 48 patients with NNIAC, 26 patients were included. Oxcarbazepine, Gabapentin, and Lamotrigine were prescribed among 19 (73%) patients, 6 (23%) patients, and 1 patient (4%), respectively. After treatment, 24 (92.3%) patients described improvement of vestibular symptoms, and 16 (76.2%) reported improvement of auditory symptoms. After treatment with antiepileptic drugs, ipsilateral IPL I-III latencies decreased (less than 2.3 ms) in 16 (84.2%) patients (23 ears out of 42). Conclusions: A low dose of anti-epileptic monotherapy for NNIAC could be effective over the long term and is generally well-tolerated. Further studies are needed to provide more solid evidence of the efficacy and safety of anti-epileptic drugs on a larger number of patients with NNIAC.

Keywords: antiepileptic therapy; narrowed internal auditory canal; neuro vascular cross compression; vestibular paroxysmia.

Figure 1

3D T2 high-resolution MRI (DRIVen Equilibrium pulse) of the IAC; measurement of IAC diameter in axial (A) and coronal plane (B) evoking a right severely narrowed IAC. IAC: internal auditory canal. Echo time 157, Repetition time 1000, slices thickness 0.4, Turbo factor 40, Matrice 500 × 500, voxel size: 0.4 × 0.4 isotropic).

Figure 2

Tomodensitometry (ultrahigh resolution at 140 kV and 200 mAs/section) of temporal bone (same patient, not included). Slices were acquired helically in the axial plane at a nominal 0.625 mm slice thickness with a 50% overlap of 0.312 mm. The primary images were retargeted to the axial and coronal planes of the lateral semicircular canal to a 60 mm field of view with a 512 matrix for an isometric voxel. Narrowing is confirmed in axial (A) and coronal plane (B).