Microsurgical Decompression of the Cochlear Nerve to Treat Disabling Tinnitus via an Endoscope-Assisted Retrosigmoid Approach: The Padua Experience

Arachnoid Cysts of the Internal Auditory Canal: Multiplanar Magnetic Resonance Imaging With Audio-Vestibular Correlates

OBJECTIVES/HYPOTHESIS

To investigate prevalence, radiological characteristics, and functional correlates of arachnoid cysts (AC) of the internal auditory canal (IAC) region, including associations of nerve compression with auditory/vestibular symptoms and asymmetrical audiogram or vestibular testing.

STUDY DESIGN

Retrospective study.

METHODS

T2-weighted magnetic resonance imaging (MRI) studies of IACs were retrospectively analyzed from 1247 patients with asymmetric auditory or vestibular symptoms. Patients with radiological findings of AC of the IAC were identified. Multiplanar analysis was used to analyze cyst position in the IAC and assess nerve displacement or compression. Size, position, and presence of nerve compression were correlated with symptoms.

RESULTS

Twenty-four patients had a cyst in the middle or fundus in the IAC. Diameter (P = .04) and position (P = .002) of AC were associated with symptoms. Sagittal analyses identified displacement versus compression (P = .003) more reliably than axial imaging. Symptom laterality was associated with the site of radiological abnormality. Vestibular nerve compression was associated with vertigo (P = .0001), and cochlear nerve compression was associated with auditory symptoms (P < .0001).

CONCLUSIONS

In a retrospective series of patients undergoing MRI of IACs for asymmetric auditory or vestibular impairment, clinical symptom profile correlated with blinded assessment of IAC lesions.

LEVEL OF EVIDENCE

4 Laryngoscope, 131:2323-2331, 2021.

A minimally invasive endoscope assisted retrosigmoid approach for removal of arachnoid cysts in the internal auditory canal: a step by step description

Introduction

Arachnoid cyst in the internal auditory canal is a quite rare pathology but due to its compressive action on the nerves in this district should be surgically removed. Several surgical techniques have been proposed but no surgeons have used the minimally assisted endoscope retrosigmoid approach for its removal.

Objective

To investigate the feasibility of using a minimally invasive endoscope assisted retro-sigmoid approach for surgical removal of arachnoid cysts in the internal auditory canal.

Methods

Minimally invasive endoscope assisted retrosigmoid approach allows to access to the internal auditory canal through a minimally invasive retrosigmoid approach that combines the use of a microscope and an endoscope. It is performed in six steps: soft tissue step, bone step, dura step, cerebellopontine angle step (performed using an endoscope and a microscope), microscope-endoscope assisted arachnoid cysts removal and closure. We tested minimally invasive endoscope assisted retrosigmoid approach for removal of arachnoid cysts in the internal auditory canal on two human cadaveric heads (specimens) of subjects affected from audio-vestibular disorders and with arachnoid cysts in the internal auditory canal confirmed by magnetic resonance imaging.

Results

The mass was completely and successfully removed from the two specimens with no damage to the nerves and/or vessels in the surgical area.

Conclusion

The results of our study are encouraging and support the feasibility of using minimally invasive endoscope assisted retrosigmoid approach for removal of arachnoid cysts in the internal auditory canal. While further clinical in-vivo studies are needed to confirm the accuracy and safety of using the minimally invasive endoscope assisted retrosigmoid approach for this specific surgery, our group has successfully used the minimally invasive endoscope assisted retrosigmoid approach in the treatment of microvascular compressive syndrome, schwannoma removal and vestibular nerve resection.