Arachnoid cyst in the internal auditory canal causing fluctuating facial paresis in a child

A lesion restricted to the internal auditory canal (IAC) proves to be a vestibular schwannoma in its early natural history more than 90% of the time. While meningiomas and facial nerve schwannomas constitute most of the remaining pathologies in this region, there are few reports of rare lesions like cavernomas, haemangiomas, lipomas, epidermoids and arachnoid cysts (ACs) [9]. Literature reveals that the incidence of lesions limited to the IAC is lesser in the paediatric age group than in adults. In this first-of-its-kind report in indexed paediatric literature, we describe an arachnoid cyst in the IAC rendered singular by the fluctuant clinical course of the facial paresis that its biological behaviour had effected. In the previous two reports in children [16, 17], the ACs had presented with progressive cranial nerve dysfunction.