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.