Congenital duplication of mastoid segment of facial nerve: A rare case report
A 15-year-old female presented to the ENT department at our hospital with history of progressive hearing loss detected at school age. There was no history of either pus discharge or ear pain. Also, there was no history of any congenital infection, trauma, or any surgery. Clinical examination showed well-formed pinna with atresia of external auditory canal. There was conductive type of hearing loss. No facial nerve abnormalities were detected. Audiometry study showed low-frequency hearing loss in the right ear up to 60 dB. Patient underwent high-resolution computed tomography (HRCT) of temporal bone in our department.\nHRCT temporal bone showed atresia of the right external auditory canal. Middle ear ossicles were dysplastic with hypoplastic malleus which was fused with deformed incus []. Stapes was absent. The inner structures, cochlea, vestibule, and semicircular canals, were unremarkable. We traced the course of facial nerve and found duplication of mastoid segment of facial nerve with two stylomastoid foramina on the right side []. Mastoid segment of the facial nerve divides into lateral and medial segments with larger lateral segment branch which carries enlarged chorda tympani branch and medial segment branch continues as tympanic branch of the facial nerve []. There was no duplication of tympanic and labyrinthine segments of the facial nerve [].