Accidental Explantation of a Cochlear Implant in a Child Who
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A 9 Y/F female as first seen at the age of 2 years for delayed speech and language development. There was an antenatal history of maternal rubella infection in the first trimester. Clinical examination of the external ear canals and tympanic membranes, then, was unremarkable. She was diagnosed with bilateral sensorineural hearing loss at a profound level for which cochlear implantation was recommended. She had right cochlear implant surgery (Advanced Bionics HiRes 90K HiFocus 1J) performed at another centre when she was 2.5 years of age. After surgery, she returned for regular audiological and auditory-verbal therapy follow-ups.

Audiologically, she was doing fine until at 3 years after implantation when she started to experience nonauditory stimulation during mapping. Whenever electrode 16 (the most proximal electrode) was stimulated, she would experience throat irritation and coughing episodes. She lost her auditory perception at electrode 16 (even at elevated M-levels of more than 400CU). Six months later, she reported pain and discomfort upon stimulation of electrodes 15 and 16. At 5 years after implantation, her score on a speech test was 80% without lip reading.

At 6 years after implantation, she returned for an urgent medical consult & gave the history of suddenly experiencing severe pain and complete loss of hearing during an aural toilet procedure in the clinic the day before. On examination, the tip of the electrode array could be seen in the external ear canal (EAC). The eardrum appeared to be perforated with the presence of cholesteatoma debris in the middle ear and EAC. The electrode array was probably exposed in the EAC secondary to the development of cholesteatoma as a complication of cochlear implantation.

Indeed, X-ray and CT scan performed on the same day confirmed that explantation had taken place with the electrode array lying in the EAC. The family was counseled accordingly. It was recommended that the cholesteatoma be eradicated and that a new device be reimplanted. Although these could be performed in 1 stage, the possibility of a 2-stage procedure was discussed.

Reimplantation surgery was carried out 2 days later. Intraoperatively, cholesteatoma was seen in the middle ear. Embedding the electrode array, diseased tissue extended into the mastoid cavity through posterior tympanotomy. With a canal wall down mastoidectomy, complete clearance of gross disease could be achieved. Soft tissue had formed around the cochleostomy site resulting in obstruction of the cochleostomy opening.

The second side cochlear implantation (Advanced Bionics HiRes 90K HiFocus Midscala) was carried out in the left ear without any problems. The blind sac was initially intact but started to breakdown about 3 weeks postsurgery. As it did not heal with medical treatment, she underwent reparative surgery with abdominal fat grafting 1 month later. The blind sac was healthy since and had remained so at least 2 years after surgery.

The right implant was activated 2 weeks after reimplantation and the left implant 3 months after that. All the electrodes could be activated with mapping parameters on both sides falling within normal limits. The adaptation to progressive maps of increasing loudness was well tolerated with no further nonauditory stimulation. At 1 year after surgery, she achieved a 100% speech test score on her reimplanted side and 63% on the opposite side. Aided hearing thresholds of 20 dB from 250 Hz to 8000 Hz were attained on both sides. With her new implants, she experienced increased awareness of very soft sounds and was doing well in mainstream school.