For those reasons, “we start all of our adult patients on CT scans,” Dr. Fishman said. “Is it a solution for all patients? Of course not.” In fact, Dr. Fishman authored a recent review article that outlines the wide variety of possible cochlear-vestibular anomalies that can require adjunctive MRI scans (Otolaryngol Clin North Am. 2012;45:1-24). The more severe the malformation, he noted, the more helpful it can be to have MRI images guiding pre-operative evaluations. In one such condition, known as a common cavity, the cochlea and vestibule come together into a common rudimentary cavity. In one study cited by Dr. Fishman, common cavities accounted for 26 percent of the congenital inner-ear malformations detected (Laryngoscope. 1987;97:2-14). In such patients, he noted, “the canal that houses the auditory nerve is extremely narrow, and you really need an MRI to adequately visualize the nerve.” In such cases, he explained, MRI helps the surgeon determine which ear is the best option for receiving the cochlear implant. “The side that looks bigger—the one that will have the optimal nerve conduction—that’s the side you want to go after,” Dr. Fishman said. “You really can’t get that type of information from a CT scan alone.”
Explore This IssueMay 2012
As for pediatric patients, “that’s a bit more complicated, but overall, factors such as a history of infection should definitely steer you towards MRI: It’s best at visualizing what’s going on inside the cochlea, whether it’s scarring or fluid build-up or other processes that can influence implantation,” he said.
As far as any ultimate answer to the question of which scan is best for pre-operative CI evaluation, “there really is no clear overall winner: It depends on the patient, any history that points to a potential cause for the hearing loss and also the surgeons’ comfort level with a particular scan,” he said.
Disclosures: Dr. Papsin disclosed that he is on the Speaker’s Bureau for the Cochlear Americas Corporation. Drs. Fishman, Hajioff and Roland had no relevant financial relationships to disclose.