1
Introduction
Cochlear implant is a viable rehabilitation option for sensorineural hearing loss in post-irradiated patients . The retro-cochlear auditory pathways appear to remain functionally intact in the long term in patients who have had irradiation for nasopharyngeal carcinoma, and the overall hearing outcomes post-cochlear implant were similar in post-irradiated patients and patients who had no prior irradiation .
Complications post-cochlear implantations are rare. In a retrospective study conducted by Wang, J. T. et al., covering a 30-year experience in a single cochlear implant centre, revision surgery was needed in 8.3% of cases. The most common indication for revision surgery was device failure (57.8%). Migration/extrusion (23.4%) and infection/wound complication (17.0%) were the next most common indications .
To date there have been no studies comparing the incidence of complications post-cochlear implantation in irradiated versus non-irradiated temporal bones.
2
Case report
The patient was a 56-year-old Chinese male with a background history of nasopharyngeal carcinoma, who completed irradiation therapy in 1991. Post-treatment he had progressive hearing loss. In the right ear, there was chronic suppurative otitis media with a central perforation of the tympanic membrane. He underwent right cochlear implantation with right radical mastoidectomy, blind sac closure of the external auditory canal and fat graft obliteration of the middle ear and mastoid cavity in January 2010. He underwent a sequential left cochlear implantation via a posterior tympanotomy approach without radical mastoidectomy or closure of the external auditory canal because the left tympanic membrane was intact. In both operations, a cochleostomy was made for the insertion of the electrode arrays and the HiRes 90K cochlear implant was used.
6 years later, he presented with complaints of a left ear itch and was noted to have an exposed electrode in the left external auditory canal. The posterior canal wall was deficient and the antrum was visible. However, the mastoid cavity was not exposed and was sealed by a layer of squamous epithelium. The appearance was similar to that after an atticoantrostomy. The electrode ran through the external ear canal in a posterior superior to an anterior inferior direction, passing directly through the pars tensa, with a good seal around it ( Picture 1 ).
There was no obvious sign of infection and soundfield testing revealed no deterioration of sound perception in this ear.
A CT temporal bone was done. This showed that the electrode arrays were present in the basal, middle and apical turns of the left cochlea. Compared to the right side, the posterior wall of the external auditory canal appeared to have broken down, exposing a short segment of the extra cochlear course of the electrode (see Pictures 2 and 3 ). The electrode arrays of the right cochlear implant were within the basal and middle turn and the extra cochlear course of the electrode was completely embedded within the soft tissue on the right.
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