Cochlear implantation in 3 patients with osteogenesis imperfecta: imaging, surgery and programming issues

Osteogenesis imperfecta (OI) is a heterogeneous disease of the connective tissue caused by a defective gene that is responsible for the production of collagen type I, leading to defective bone matrix and connective tissue. Hearing loss affects 35-60% of the patients and will progress to deafness in 2-11% of OI patients for whom cochlear implantation may become the only remaining treatment option. Three patients with OI were retrieved from the Nijmegen Cochlear Implant Centre's database. Most of the specific observations in ear surgery on patients with OI, such as brittle scutum, sclerotic thickening of the cochlea, hyperplastic mucosa in the middle ear and persistent bleeding, were encountered in these 3 patients. In case 3, with severe deformities on the CT scan, misplacement of the electrode array into the horizontal semicircular canal occurred. In all 3 cases, programming was hindered by nonauditory stimulation. Even after reimplantation, nonauditory sensations lead to case 3 becoming a nonuser. Averaged electrode voltages in case 3 were deviant in accordance with an abnormally conductive otic capsule. Spatial spread of neural excitation responses in cases 1 and 2 suggested intracochlear channel interaction for several electrodes, often in combination with facial nerve stimulation (FNS). In case 1, the estimated pitch of the electrodes that caused FNS varied consistently. Despite the electrophysiological changes, after 1-year follow-up, open set phoneme scores of 81% and 78% were reached in cases 1 and 2, respectively. When aware and prepared for the specific changes of the temporal bone in OI, cochlear implantation can be a safe and feasible procedure. Preoperative imaging is recommended to be fully informed on the morphology of the petrosal bone. In case of severe deformities on the CT scan, during counseling the possibility of misplacement should be mentioned. Rehabilitation is often hindered by FNS requiring frequent refitting.