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

“We had already been doing dual imaging in most of our pediatric patients,” he said. “But it really wasn’t working for us: It was expensive to order both tests, and we just weren’t sure the cost was justified by the added diagnostic information we were getting.” Moreover, “because our CT and MRI equipment were at opposite ends of our hospital for several years, trying to get both scans done in children while they were under the same general anesthetic was really proving to be difficult.”

So Dr. Hajioff and his colleagues compared CT and MRI, hoping to determine whether one imaging modality was superior enough to become the imaging test of choice for most patients (Cochlear Implants Int. [published online ahead of print June 29, 2011). The study, which included 158 adults and children, found that both scans detected 44 significant abnormalities pre-operatively. Of those, 20 were considered critical to the selection of side for implantation, surgical procedure or decision to operate. MRI was able to detect all of those abnormalities (95 percent confidence interval [CI]: 0-2.3 percent). In contrast, CT alone missed 10 critical abnormalities (95 percent CI: 3.1-11.3). These findings were consistent in adults and children, the investigators reported.

“The simplistic conclusion from these findings would be that all comers should get MRI and that to save health care resources and minimize radiation exposure, we should forego CT scans,” Dr. Hajioff said. But, as convincing as the data are, real-world clinical situations often require a more nuanced approach, he added.

For example, although most of his adult patients only get an MRI, if there is a history of any prior surgery that might have altered the mastoid or if the patient has had meningitis, which can cause ossification, “we order a CT scan as well. It really is superior in imaging bone,” Dr. Hajioff said. “So we haven’t completely abandoned CT.”

Similarly, although MRI is slowly becoming the preferred option in children, adjunctive CT scans are still sometimes ordered. “But I am only [using CT] in cases where there is an increased likelihood that it might pick up something of interest, for example, kids with a history of severe infections, meningitis or craniofacial dysmorphic syndromes,” Dr. Hajioff said. “Those children get both scans in the same sitting.”

He added another reason why the study results favoring MRI shouldn’t be applied too aggressively, at least in children; like any clinical research, the study had some limitations. “Probably the biggest is the study size. Even though the number of patients [158] is larger than most previous studies, it’s still a relatively small sample. In our practice alone, we’ve probably done more than 500 implants. So larger numbers might have led to more robust—and perhaps different, although I doubt it—conclusions.”