The presence of a cochlear implant (CI) used to be an absolute contraindication for MRI unless the internal magnet was surgically removed prior to scanning. More recently implant manufacturers produced devices labelled as MR conditional.
The main complications in MRI arise from the magnetic force and torque on the internal magnet from B0. To address this, implant manufacturers advised bandaging around the head to keep the magnet in place, often supplying a kit to achieve this. For fields above 1.5 T surgical removal of the internal magnet was generally required. For head scans ferromagnetic artefacts can be severe, potentially degrading the diagnostic value of the examination.
Despite the use of bandages there are numerous reports of magnet dislodgement, polarity reversal (by flipping), and unbearable patient pain with an adverse incident rate of around 30% [1-4]. Case reports of CI dislodgement also abound [5-11]. The definition of MR conditional that the “device poses no additional risk to the patient when introduced to the MR environment under specified conditions” is hard to reconcile with cochlear implants. Now it appears that one implant manufacturer has agreed, advising the removal of the internal magnet prior to MRI:
The external components are generally MR unsafe and must not be brought into the MR environment.
Thanks to Trader @IRGShellharbour
Useful information from the British Cochlear Implant Group can be found at https://www.bcig.org.uk/safety/
1. Tam, Y. C., Graves, M. J., Black, R.T. et al. (2010). Magnetic resonance imaging in patients with cochlear implants and auditory brain stem implants. Cochlear Implants International 11 sup.2:48–51.
2. Kim, B., Park, J., and Kim, J. (2015). Adverse events and discomfort during magnetic resonance imaging in cochlear implant recipients. JAMA Otolaryngology Head & Neck Surgery 141: 45–53.
3. Carlson, M.L, Neff, B.A., Link, M.J. et al. (2015). Magnetic Resonance Imaging with Cochlear Implant Magnet in Place: Safety and Imaging Quality. Otology & Neurotology 36:965–971.
4. Young, N.M., Rojas, C., Deng, J. et al. (2016). Magnetic resonance imaging of cochlear implant recipients. Otology & Neurotology 37:665–671.
5. Yun, J.M., Colburn, M.W., and Antonelli, P.J. (2005). Cochlear implant magnet displacement with minor head trauma. Otolaryngology Head Neck Surgery 133:275–277.
6. Deneuve, S., Loundon, N., and Leboulanger, N. (2008). Cochlear implant magnet displacement during magnetic resonance imaging. Otology & Neurotology 29:789–790.
7. Jeon, J.H., Bae, M.R., Chang, J.W. et al. (2012). Reversing the polarity of a cochlear implant magnet after magnetic resonance imaging. Auris Nasus Larynx 39:415–417.
8. Cuda, D., Murri, A. and Suggo, G. (2013). Focused tight dressing does not prevent cochlear implant magnet migration under 1.5T MRI. Acta Otorhinolaryngologia Italica 33: 122–136.
9. Keereweer, S., Van der Schroeff, M.P., and Pullens, B. (2014). Case report: Traumatic displacement of a cochlear implant magnet. Annals of Otology, Rhinology & Laryngology 123:229–231.
10. Hassepass, F., Stabenau, V., Maier, W. et al. (2014). Revision surgery due to magnet dislocation in cochlear implant patients: an emerging complication. Otology & Neurotology 35:29–34.
11. Leong, W. and Yuen, H. (2018). Dislocation of cochlear implant magnet during 1.5 tesla magnetic resonance imaging despite head bandaging, and its repositioning using an endoscopic approach. Journal of Laryngology and Otology 132:943–945
Modified excerpt from Essentials of MRI Safety, publication date June 2020.