Nadine Schart-Morén1, Karin Hallin1, Sumit K Agrawal2, Hanif M Ladak3, Per-Olof Eriksson1, Hao Li1, Helge Rask-Andersen1. 1. a Department of Surgical Sciences, Section of Otolaryngology, Head and Neck Surgery , Uppsala University Hospital , Uppsala SE-75185 , Sweden. 2. b Department of Otolaryngology - Head and Neck Surgery , Western University, 1151 Richmond Street , London , ON , Canada, N6A3K7. 3. c Department of Otolaryngology - Head and Neck Surgery, Department of Medical Biophysics, Department of Electrical and Computer Engineering , Western University, 1151 Richmond Street , London , ON , Canada, N6A3K7.
Abstract
OBJECTIVES: Dehiscence between the cochlear otic capsule and the facial nerve canal is a rare and relatively newly described pathology. In cochlear implantation (CI), this dehiscence may lead to adverse electric facial nerve stimulation (FNS) already at low levels, rendering its use impossible. Here, we describe an assessment technique to foresee this complication. METHODS: Pre- and postoperative computed tomography (CT) scans and intraoperative electrically evoked auditory brainstem response (e-ABR) measurements were analyzed in two patients with cochlear-facial dehiscence (CFD). RESULTS: Because of the relatively low resolution, the confirmation of CFD with a clinical CT was difficult. The e-ABR displayed a large potential with 6 and 7.5 ms latency, respectively, which did not occur otherwise. DISCUSSION: Potential strategies to resolve and manage FNS are described. CONCLUSION: Prediction of FNS by assessing the distance between the labyrinthine portion of the facial nerve and the cochlea is difficult using conventional CT scans. A large evoked late myogenic potential at low stimulation levels during intraoperative e-ABR measurement may foresee FNS at CI activation.
OBJECTIVES: Dehiscence between the cochlear otic capsule and the facial nerve canal is a rare and relatively newly described pathology. In cochlear implantation (CI), this dehiscence may lead to adverse electric facial nerve stimulation (FNS) already at low levels, rendering its use impossible. Here, we describe an assessment technique to foresee this complication. METHODS: Pre- and postoperative computed tomography (CT) scans and intraoperative electrically evoked auditory brainstem response (e-ABR) measurements were analyzed in two patients with cochlear-facial dehiscence (CFD). RESULTS: Because of the relatively low resolution, the confirmation of CFD with a clinical CT was difficult. The e-ABR displayed a large potential with 6 and 7.5 ms latency, respectively, which did not occur otherwise. DISCUSSION: Potential strategies to resolve and manage FNS are described. CONCLUSION: Prediction of FNS by assessing the distance between the labyrinthine portion of the facial nerve and the cochlea is difficult using conventional CT scans. A large evoked late myogenic potential at low stimulation levels during intraoperative e-ABR measurement may foresee FNS at CI activation.
Authors: Iris Burck; Rania A Helal; Nagy N N Naguib; Nour-Eldin A Nour-Eldin; Jan-Erik Scholtz; Simon Martin; Martin Leinung; Silke Helbig; Timo Stöver; Annette Lehn; Thomas J Vogl Journal: Eur Radiol Date: 2021-07-05 Impact factor: 5.315