NEW YORK (Reuters Health) – Magnetic resonance imaging (MRI) machines may displace the magnets of cochlear implants or cause extreme discomfort for some wearers, according to a new study.
More than 300,000 people worldwide now have a cochlear implant, a small electronic device with an external transmitter held in place behind the ear with a magnet and an internal electrode array. The devices can help restore a sense of hearing to the profoundly deaf, according to the National Institute on Deafness and Other Communication Disorders.
“There have been several reports of adverse events, such as magnet displacement and polarity changes, following MRI in patients with cochlear implants,” said senior author Dr. Jae Young Choi of the Department of Otorhinolaryngology at Yonsei University College of Medicine in Seoul, South Korea. “The exposure of the internal magnet to a strong electromagnetic field can induce significant magnetic forces and cause displacement of the implant.”
It would make sense that the electromagnetic field in an MRI may interact with the magnet in a cochlear implant to either cause pain or to distort the results of the scan, but as the authors note, the U.S. Food and Drug Administration has approved certain MRIs for patients with cochlear implants in specific cases.
Some implants have removable magnets, in which case it should be removed. Other patients should use head dressings while in the magnetic machine.
For the new study, Choi’s team reviewed the medical records of 18 patients with cochlear implants who had MRIs between 2003 and 2014, including 12 brain scans and 18 body scans. Some patients had multiple scans.
Thirteen of the 18 patients made it through their MRIs without complications. Five people could not complete their scans due to pain, one experiencing magnet displacement and another requiring surgery for magnet removal and reinsertion.
Pain generally stopped when the MRI was over, except for the patient with magnet displacement.
“If the magnet is displaced, it can be easily replaced by surgery under local anesthesia,” Choi told Reuters Health by email.
Even with protective bandages, some patients felt significant pain.
The three patients with the most serious side effects of the scan did not appear to have damaged hearing performance later, according to results in JAMA Otolaryngology-Head & Neck Surgery.
“Appropriate sedation and head positioning can alleviate patient discomfort or pain during MRI scans,” Choi said. “Therefore, patients with cochlear implants who undergo MRI scans should be carefully monitored and measures should be taken to minimize the likelihood of adverse events.”
Many doctors think that as long as the patient is not injured, the MRI can be performed safely and is acceptable, according to Dr. Emanuel Kanal of the department of radiology at the University of Pittsburgh Medical Center, who wrote an editorial accompanying the study.
“The problem is that it sometimes may be painful and the physician may not recognize or be aware of that,” Kanal told Reuters Health by phone.
This study indicates that doctors ordering an MRI for patients with cochlear implants should discuss the possibility of pain with their patient beforehand, he said.
“There’s almost never any sort of sensation, let alone pain, during an MRI,” Kanal said. “No one warns them because 99.9 percent have no pain, so their patients may not report it.”
Sometimes, even if it is painful, it is still appropriate for the patient to be scanned, but doctors and patients should still be aware of the possibility, he said.
SOURCE: bit.ly/1vjBhHC, bit.ly/1vJUq6U JAMA Otolaryngology, Head & Neck Surgery, online November 20, 2014.