OTOLOGY Reliability of cone beam computed tomography in scalar localization of the electrode array: a radio histological study Mathieu Marx • Frank Risi • Bernard Escude ´ • Irfan Durmo • Christopher James • Fre ´de ´ric Lauwers • Olivier Deguine • Bernard Fraysse Received: 19 November 2012 / Accepted: 13 March 2013 / Published online: 28 March 2013 Ó Springer-Verlag Berlin Heidelberg 2013 Abstract Postoperative imaging plays a growing role in clinical studies concerning prognostic factors in cochlear implantation. Indeed, intracochlear position of the cochlear implant has recently been identified as a contributor in functional outcomes and radiological tools must be accu- rate enough to determine the final placement of the elec- trode array. The aim of our study was to validate cone beam computed tomography as a reliable technique for scalar localization of the electrode array. We performed therefore a temporal bone study on ten specimens that were implanted with a perimodiolar implant prototype. Cone beam reconstructions were performed and images were analyzed by two physicians both experienced in cochlear implant imaging, who determined the scalar localization of the implant. Temporal bones then underwent histological control to document this scalar localization and hypothet- ical intracochlear lesions. In four cases, a dislocation from scala tympani to scala vestibuli was suspected on cone beam reconstructions of the ascending part of the basal turn. In three of these four specimens, dislocation in pars ascendens was confirmed histologically. In the remaining temporal bone, histological analysis revealed an elevation with rupture of the basilar membrane. Histological assessment revealed spiral ligament tearing in another bone. We conclude that cone beam is a reliable tool to assess scalar localization of the selectrode array and may be used in future clinical studies. Keywords Cochlear implant Á Cone beam computed tomography Á Dislocation Á Temporal bone histology Introduction Cochlear implants can restore excellent speech recognition, but variability in outcomes remains a constant feature especially in post-lingually deafened adults [1–4]. Among factors accounting for this variability, duration of deafness is probably the most critical one [1, 3, 4]. Experience with CI is also reported as an important contributor in patients’ outcomes, with a potential improvement of performance up to 3.5 years after implantation [3]. Other variables, such as age for post-lingually deafened implanted adults or cause of deafness (meningitis) also contribute to the variability in CI users’ outcomes [3]. More recently, scalar localization of the electrode array and its consequences on hearing performance has also been investigated [5, 6]. Indeed, as soft surgery has been more and more promoted through the past 10 years, intracochl- ear placement of the electrode array has been the focus of increasing interest. Scala tympani is the optimal place for electrode array insertion, as terminal sensorineural M. Marx (&) Á B. Escude ´ Á C. James Á O. Deguine Á B. Fraysse Department of Otology-Neurotology and Skull Base Surgery, Purpan University Hospital, Place du Docteur Baylac, 31059 Toulouse, France e-mail: marx.m@chu-toulouse.fr M. Marx Á O. Deguine CerCo, UMR 5549, CNRS-Universite ´ Paul Sabatier, Toulouse, France F. Risi Á I. Durmo Á C. James Cochlear Limited, Sydney, Australia B. Escude ´ Department of Neuroradiology, Clinique Pasteur, Toulouse, France F. Lauwers Department of Maxillo Facial Surgery, Purpan University Hospital, Toulouse, France 123 Eur Arch Otorhinolaryngol (2014) 271:673–679 DOI 10.1007/s00405-013-2448-6