The compatibility of MRIs and cochlear implants

By Mandy Ennis

There is very interesting research being done currently and in recent years on the subject of MRIs, a commonly used imaging tool that provides exceptional spatial resolution, and their use on individuals with cochlear implants. Given that MRI stands for Magnetic Resonance Imaging, it comes as no surprise that MRIs relate directly to the study of physics through the use of magnetism. Although magnetism is not a subject we have discussed thoroughly in this class, it is still relevant given the emphasis of this class on force and related physical variables. 

Sonnenberg et al. (2002) conducted research on the compatibility of MRIs and cochlear implants, devices that use a magnetic field between the two main components of the implant, the external transmitter on the scalp and the internal stimulator-receiver, which is surgically implanted into the skull and cochlea, to keep the device in place and functioning properly. Given that MRIs use magnetism to visualize internal structures within the body, it is important to understand the interaction between cochlear implants and MRIs and their respective magnetic forces to determine their safety when used in combination. This research by Sonnenberg et al. (2002) examined the magnitude of the magnetic force that is able to be exerted on the cochlear implant by the MRI without causing injury to the patient; such potential injury could include skull fracturing and pressure on the brain, as well as dysfunction of the cochlear implant. For example, Bawazeer et al. (2019) reported an occurrence of demagnetization of the cochlear implant, which necessitated removal and reimplantation, and another occurrence of  “considerable pain” in two different patients with cochlear implants that underwent MRIs. Using various materials to attach the stimulator-receiver, as well as varying skull thicknesses, Sonnenburg et al. (2002) measured the magnitude of magnetic force exerted by the MRI on the implant and the displacement of the internal stimulator that would fracture the skull. Compared to the acceptable “safe” magnetic force that is typically experienced by the wearer of a cochlear implant without causing injury, they found that in general, MRIs should be safe for use in individuals with cochlear implants; however, there is still precaution regarding compatibility of cochlear implants and the use of MRIs (“Johns Hopkins Cochlear Implants MRI Protocol”). Many factors influence the safety of undergoing an MRI with a cochlear implant, such as the length of time since the implantation (since the skull should ideally heal fully before undergoing any magnetic imaging) and the thickness of the patient’s skull.  

A Google search of the name of the author (Robert E. Sonnenberg, MD) revealed that Dr. Sonnenburg is an ENT-otolaryngologist in Wisconsin. I wasn’t able to determine his undergraduate education, but he received his MD from the Medical College of Wisconsin in 2000 and completed his internship and residency at the University of North Carolina, Chapel Hill (​U.S. News & World Report​ ). Although it is not known whether Dr. Sonnenburg has a background in the field of physics, this research directly relates to some of the topics that we have addressed in our class, as we have discussed the force that can be applied to the head without causing injury. In general, our class has also focused on forces and displacement, which is directly related to this research. 

Sources: 

1. Bawazeer, Naif, et al. “Magnetic Resonance Imaging after Cochlear Implants.” ​Journal of Otology​ , Chinese PLA General Hospital, Mar. 2019, www.ncbi.nlm.nih.gov/pmc/articles/PMC6424707/.

2. “Dr. Robert E. Sonnenburg Jr.” ​U.S. News & World Report​ , U.S. News & World Report, health.usnews.com/doctors/robert-sonnenburg-jr-228323.

3. “Johns Hopkins Cochlear Implant MRI Protocol.” ​Johns Hopkins Medicine​ , Johns Hopkins Hospital, 10 Dec. 2018, www.hopkinsmedicine.org/otolaryngology/specialty_areas/listencenter/resources/mris-at-hopkins .html.