Computed Tomography and/or Magnetic Resonance Imaging Before Pediatric Cochlear Implantation? Developing an Investigative Strategy

Abstract

Dual-modality imaging with HRCT and MR of petrous bone and MR brain in the precochlear implant pediatric population detects abnormalities related to deafness, which would not otherwise be found using either modality alone. There is overlap between the imaging modalities in the type of abnormalities detected, and we present a case for selective use of HRCT within a diagnostic algorithm, using the patient risk factors we have identified.

Enlarged Vestibular Aqueduct in Pediatric SNHL

“…18 In contrast, Trimble et al compared the utility of HRCT and MRI prior to cochlear implantation in children. 19 Their study indicated that the best protocol was both MRI and HRCT to image the temporal bone because neither modality was sufficient to detect all abnormalities related to deafness independently. A greater percentage of radiologic abnormalities were identified using HRCT scan as compared to MRI, 59% vs. 32% respectively.…”

Pediatric Sensorineural Hearing Loss, Part 1: Practical Aspects for Neuroradiologists

“…Historically, CT has been the study of choice, but MR imaging has become increasingly popular as concerns mount over the risks associated with ionizing radiation exposure, particularly in children. 5 Trimble et al 6 have suggested that dual-technique imaging with high-resolution temporal bone CT and MR imaging identifies a substantially larger number of abnormalities in children being evaluated for cochlear implantation than either technique alone; however, whether the additional diagnostic yield of this strategy justifies the added cost of routinely performing both studies or even alters outcomes remains an area of debate.…”

“…[7][8][9][10] High-resolution temporal bone CT is better for assessing bone detail and can be performed at lower cost and in less time, resulting in less frequent need for sedation or anesthesia compared with MR imaging. 6,10 At our institution, MR imaging is the preferred initial imaging test performed in children with newly diagnosed SNHL. Our pediatric temporal bone MR imaging protocol, which is performed in approximately 20 minutes, includes either highresolution FSE T2-weighted images (TR/TE/NEX, 1000/136 ms/1; echo-train length, 21; flip angle, 180°; FOV, 140 mm; matrix size, 192) or CISS images (TR/TE/NEX, 5.42-12.25/ 2.42-5.9 ms/1-2; flip angle, 50°-80°; FOV, 120 -180 mm; matrix size, 256) through the temporal bones, as well as standard spin-echo T1-weighted images, FSE T2-weighted images, fluid-attenuated inversion recovery, and diffusion-weighted images through the entire brain.…”

Pre-, Intra- and Post-Operative Imaging of Cochlear Implants

“…In addition, the width of the cochlear aperture and of the internal auditory canal can serve as an indirect indicator of possible hypoplasia of the cochlear nerve through assessment via CT. Its cost is lower and the scanning time is much shorter compared to MRI, with less need for anesthesia in children. CT also allows the simultaneous delineation of the skull base and middle and inner ear anomalies [15,16]. MRI, on the other hand, provides better soft tissue contrast and is the modality of choice for imaging of the cochlear nerve.…”

“…CT as well as MRI provide specific information and may be considered as complementary to one another. The combined use of both modalities for preoperative imaging before cochlear implantation may identify more relevant abnormalities, which would not be detected using only a single modality [15]. Technique of CT Imaging !…”