The MRI-CT Faceoff in Pre-Operative Coclear Implant Staging

What of the “old guard” of surgeons cited by Dr. Papsin, who tend to prefer CT scans as a sole imaging modality? “I don’t quarrel with that approach,” Dr. Hajioff said. “There are many surgeons who feel they need the roadmap of bony structures afforded by the CT scan in front of them before they operate. Personally, I am getting more comfortable not having that in place. Sure, you may not be able to see exactly where the facial nerve is, or see the sigmoid sinus in relation to other inner-ear structures, when you only order an MRI. But for me, the MRI tells you what you need to know; the rest of it you can work out while you are operating.”

Bottom line? “I think the CT scan, in some cases, is more of a psychological prop than an essential diagnostic tool,” he said.

MRI Gets Another Nod

Peter Roland, MD, professor and chairman of otolaryngology/head and neck surgery and professor of neurologic surgery at the University of Texas Southwestern Medical Center in Dallas, is also in the camp that favors MRI for certain patients and clinical settings. That stance, like those of Drs. Papsin and Hajioff, is based in part on a head-to-head trial of CT and MRI that Dr. Roland and his colleagues conducted in 56 children (Otol Neurotol. 2005;26:976-982).

“We found that MRI was more consistently able to identify types of abnormalities—for example, asymmetric nerve aplasia and cochlear obstruction—that were most likely to influence the implantation process,” Dr. Roland told ENT Today. Coupled with the fact that MRI is much more effective in identifying soft-tissue abnormalities in the inner ear, we felt that the study supported what we had known empirically for some time: that MRI is the superior scan,” Dr. Roland said.

He added that it’s not just the surgeons who prefer MRIs. “Most, if not all, of our pediatric neuroradiologists believe that they are better able to diagnose abnormalities of the cochlea itself using MRI than CT, and we use MRI preferentially for the evaluations of bilateral sensorineural hearing loss. That’s because the fluid signal is more revealing than the bone signal in terms of highlighting significant defects,” he said.

Are there some findings that CT can better elucidate? “Sure,” Dr. Roland said. “CT scans are great at letting you know whether a child has a normal oval or round window, which can complicate surgery.” Additionally, he noted, CT scans can better track the middle and mastoid course of the facial nerve. Thus, the scan is more useful in identifying and characterizing facial nerve anomalies, “but we have found that anomalous nerves are almost always associated with a malformed semicircular canal or vestibule, which are easily seen on MRI. If we identify either of these abnormalities on MRI, we get a CT, but that is very infrequent.”