Arachnoidalzysten im inneren Gehörgang und Canalis facialis (Fallopius)

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.

Arachnoid cysts confined to the internal auditory canal or facial nerve canal

OBJECTIVE

To illustrate the morphological characteristics and pathological significance of arachnoid cysts confined to the internal auditory canal or facial nerve canal.

DESIGN

Retrospective case series.

SUBJECTS

Three patients' cases were reviewed, and temporal bone sections examined histologically.

RESULTS

In this series, three intracanalicular arachnoid cysts were found in the internal auditory canal and one in the facial nerve canal. All lesions consisted of distinct, space-occupying cysts with a sharp boundary with surrounding tissues. They were thin-walled and compressed the surrounding nerve trunks to a variable degree. However, there was no indication that patients suffered meatal nerve dysfunction.

CONCLUSION

Arachnoid cysts can develop within the internal auditory canal or facial nerve canal. In our series, they were asymptomatic, which is quite different from most intracanalicular arachnoid cysts encountered in clinical practice.