Cochlear implant tailored imaging protocol: What clinicians need to know

Abstract

Purpose: In pediatric population with SNHL, a radiological presurgical mapping exam is usually performed, purpose of this study is to improve the inter-rater agreement giving different imaging modalities using MDCT and MRI to facilitate identifying patients in need for surgical modification before cochlear implant. Methods and material: 120 pediatric patients ranging between 1 and 12 years with an average age of 5 years diagnosed with congenital or acquired SNHL and requiring cochlear implant (CI) after proper surgical selection were included in the study. All patients underwent combined 64 detector MDCT using pediatric low dose protocol with sagittal, Stenvers views in addition to standard axial and coronal plane reconstruction from single acquisition volume. In the same session, 3D DRIVE MRI axial plane reformatted into sagittal plane for the IAC and inner ear as well as axial T2WI/FLAIR for the whole brain. Two different head and neck radiologists blindedly reported the inner ear, cochlear nerve development, temporal bone anatomy, operative window, as well as normal variants that could hinder implantation as well as causes of central hearing loss. Findings were compared with operative findings. Results: Patients were categorized into four groups; according to the capability of electrode implant, modification of surgical techniques and expected response with high intra-observer was noted with a PABAK value of 0.96 for observer A and of 0.93 for observer B. Lower inter observer agreement was observed on an individual usage of radiological techniques for reaching diagnosis (conventional CT, MRI, or Stenvers/sagittal oblique techniques alone) with a PABAK value of 0.93, 0.78 and 0.73, respectively. A higher inter observer agreement was met on combining all these radiological modalities together (PABAK value of 0.96). Conclusion: Stenvers view efficiently makes pre-surgical mapping for the intra-cochlear electrode pathway by identifying the cochlear turns, round and oval window, vestibule and SCC as well as facial nerve canal in one view helping the surgeon in optimizing the technique. MRI identifies the fibrous labyrinthitis ossificans not detected by CT and evaluates the cochlear nerve development and integrity of central auditory pathway. Combined MDCT/MRI imaging protocol helps the clinician in proper patient categorization, optimize their surgical approach and the type of electrode. Clinical relevance/application: SNHL is a malfunction of the inner ear, vestibulocochlear nerve or central auditory pathway. Imaging helps to establish treatment regimens that improve auditory function.

Keywords

• Cochlear implant
• Sensory neural hearing loss
• Post-meningitic
• Labyrinthitis ossificans