Duplicate internal auditory canals with facial and vestibulocochlear nerve dysfunction T Y KEW 1 , A ABDULLAH 2 Departments of 1 Radiology and 2 Otorhinolaryngology, Medical Faculty, Universiti Kebangsaan Malaysia, Kuala Lumpur, Malaysia Abstract Objective: We report an extremely rare case of duplication of the internal auditory canal associated with dysfunction of both the facial and vestibulocochlear nerves. We also review the literature regarding the integrity of the facial and vestibulocochlear nerves in such cases. Case report : A 34-year-old man presented with unilateral, right-sided, sensorineural hearing loss and facial nerve palsy since childhood. Facial nerve function was observed to be House–Brackmann grade III. Computed tomography and magnetic resonance imaging demonstrated ipsilateral duplicate, vacant internal auditory canals. Based on the clinical presentation, we interpreted these radiological findings as aplasia of the vestibulocochlear nerve and severe hypoplasia of the facial nerve. Conclusion: To our best knowledge, this isthe first report of vestibulocochlear nerve aplasia and severe facial nerve hypoplasia in a case of ipsilateral duplication of the internal auditory canal. High resolution gradient echo magnetic resonance imaging sequences are advocated for assessment of neural integrity in patients with an abnormal internal auditory canal and facial and/or vestibulocochlear nerve dysfunction. Key words: Facial Paralysis; Hearing Loss, Sensorineural; Tinnitus; Abnormalities, Temporal Bone Introduction Duplication of the internal auditory canal is a rare condition. To date, only 11 cases have been reported in the literature, including one case of triplication of the internal auditory canal. 1– 9 The presence of sensorineural hearing loss on the affected side is universally detected, with absence of the ves- tibulocochlear nerve on magnetic resonance imaging (MRI) in nearly all cases (Table I). However, facial nerve function and calibre (on MRI) were normal in all reported cases in which these features were mentioned. This report describes an unusual case of unilateral dupli- cation of the internal auditory canal, with sensorineural hearing loss and facial nerve dysfunction, and also presents a review of the literature. Case report A 34-year-old man presented to our institution with a three- month history of left-sided, low frequency tinnitus. On further questioning, he claimed to have had right-sided hearing loss since childhood. He denied otorrhoea and otalgia. Occasional episodes of imbalance were reported. There was no family history of sensorineural hearing loss. His perinatal history was unremarkable, with no history of childhood meningitis or chronic otitis media. Examination of the head and neck revealed a right House –Brackmann grade III facial nerve palsy, which the patient claimed had been present since childhood. Normal tympanic membranes were noted bilaterally. The Weber test lateralised to the left, while the Rinne test showed air conduction to be greater than bone conduction. Pure tone audiometry revealed a profound sensorineural hearing loss on the right. High resolution computed tomography (CT) of the tem- poral bones demonstrated duplication of the right internal auditory canal. Both canals were narrow: the maximal cal- ibres of the superior and inferior canals measured 1.3 and 1.2 mm, respectively. The superiorly located canal showed continuity with the labyrinthine segment of the facial canal (Figure 1), while the inferiorly located canal had continuity with the cochlear aperture and singular canal (Figure 2). At the most lateral aspect of the canals, a fused portion was seen in which the bony septum which divided the canals more medially was absent (Figure 3). This fused portion occupied approximately one-third of the length of the canals. The rest of the right facial canal, from the labyrinthine segment to the mastoid segment, and including both the first and second genu, was normal in position and course. There was no focal osseous tumour of the internal auditory canal, nor any evidence of a diffuse sclerotic temporal osseous process. The left internal auditory canal was of normal calibre. The cochleae, vestibules and semicircular canals were of normal configuration bilaterally. No enlargement of the vestibular aqueducts was noted. Magnetic resonance imaging, using three-dimensional constructive interference in steady state sequencing, showed no discernible normal cisternal portion of the right Accepted for publication 17 March 2011 First published online 26 August 2011 The Journal of Laryngology & Otology (2012), 126, 66–71. CLINICAL RECORD © JLO (1984) Limited, 2011 doi:10.1017/S0022215111002258