MRI, Medical Considerations
Warnings and Precautions
With a cochlear implant, you need to be aware about the impact of some medical situations and treatments, including those described below. Discuss all warnings and precautions with your physician before undergoing any major medical procedure.
Medical Treatments Generating Induced Currents
Some medical treatments generate induced currents that may cause tissue damage or permanent damage to the cochlear implant. Warnings for specific treatments are provided below.
- Electrosurgery: Electrosurgical instruments are capable of inducing radio frequency currents that could flow through the cochlear implant electrode array. Monopolar electrosurgical instruments must not be used on the head or neck of a cochlear implant recipient as induced currents could cause damage to cochlear tissues or permanent damage to the implant. Bipolar electrosurgical instruments may be used on the head and neck of recipients. However, the cautery electrodes must not contact the implant and should be kept more than ~ 1/2 in. (1 cm) from the extracochlear electrodes.
- Diathermy: Do not use therapeutic or medical diathermy (thermopenetration) using electromagnetic radiation (magnetic induction coils or microwave). High currents induced into the electrode lead can cause tissue damage to the cochlea or permanent damage to the implant. Medical diathermy using ultrasound may be used below the head and neck.
- Neurostimulation: Do not use neurostimulation directly over the cochlear implant. High currents induced into the electrode lead can cause tissue damage to the cochlea or permanent damage to the implant.
- Electroconvulsive Therapy: Do not use electroconvulsive therapy on a cochlear implant recipient under any circumstances. Electroconvulsive therapy may cause tissue damage to the cochlea or damage to the cochlear implant.
- Ionizing Radiation Therapy: Do not use this therapy directly over the cochlear implant because it may cause damage to the implant.
Magnetic Resonance Imaging (MRI):
MRI magnetic fields can generate potentially harmful forces that may cause tissue damage or demagnetize a cochlear implant magnet. The implanted magnets can also create image artifacts in head scans which can reduce an MRI’s diagnostic value. Removal and replacement of the magnet - without the need for explantation and subsequent re-implantation - is possible with most Nucleus Cochlear Implants.
Magnetic Resonance Imaging (MRI) is contraindicated except under the circumstances described below. Recipients with a cochlear implant should not be in the room where an MRI scanner is located except under the following special circumstances.
The Cochlear Nucleus 5 (CI500 series) cochlear implant, Cochlear Nucleus Freedom cochlear implant, Nucleus 24 cochlear implant, and some Nucleus 22 cochlear implants have a removable magnet and specific design characteristics to enable them to withstand MRI up to 1.5 tesla, but not higher. Those with a magnet in place must not enter a room with an MRI operating.
If the cochlear implant’s magnet is in place, it must be removed surgically before the recipient undergoes an MRI procedure. The recipient must take off the sound processor and headset before entering a room where an MRI scanner is located.
If the implant’s magnet is still in place, tissue damage may occur if the recipient is exposed to MRI. Once the magnet is surgically removed, the quality of the MRI will be affected by the metal in the cochlear implant. Image shadowing may extend as far as ~2.5 in. (6 cm) from the implant, thereby resulting in loss of diagnostic information in the vicinity of the implant.
If your physician is unsure whether your cochlear implant has a removable magnet, the physician should use an X-ray to check the radiopaque lettering on each implant magnet. If the middle character is a ‘C’, ‘G’, ‘H’, ‘J’, ‘L’, ‘P’, ‘T’, ‘2’, ‘5’, or ‘7’, the implant has a removable magnet. Once the magnet has been removed, MRI can be performed. If you require additional information about removal of the magnet, please contact Cochlear Americas.
Prior to implantation, candidates should consult their primary care physician and implanting surgeon regarding vaccination status against organisms that cause meningitis. Meningitis is a known risk of inner ear surgery and candidates should be appropriately counseled of this risk. In addition, certain preoperative conditions may increase the risk of meningitis with or without a cochlear implant. These conditions include:
- Mondini’s syndrome and other congenital cochlear malformations
- Concurrent Cerebrospinal Fluid (CSF) shunts or drains
- Recurrent episodes of bacterial meningitis prior to implantation
- Perilymph fistulas and skull fracture/defect with CSF communication.
Loss of residual hearing
Insertion of the electrode into the cochlea will result in complete loss of residual hearing in the implanted ear.
Long-term effects of electrical stimulation by the cochlear implant
Most recipients can benefit from electrical stimulation levels that are considered safe, based on animal experimental data. For some recipients, the levels needed to produce the loudest sounds exceed these levels. The long-term effects of such stimulation in humans are unknown.
Small parts hazard
Parents and caregivers should be counseled that the external implant system contains small parts that may be hazardous if swallowed or may cause choking if inhaled.
Batteries can be harmful if swallowed. Ensure that batteries are kept out of reach of young children. If swallowed, seek prompt medical attention at the nearest emergency facility.
A blow to the head in the area of the cochlear implant may damage the implant and result in its failure. Young children who are developing their motor skills are at greater risk to receive an impact to the head from a hard object (e.g. a table or chair).
Recipients should remove the sound processor immediately if it becomes unusually warm or hot, and seek advice from their clinician. Parents and caregivers should touch their child’s (or the recipient’s) processor to check for heat if the recipient is showing signs of discomfort.
The manufacturer only recommends the use of zinc air batteries as they have been determined to be safe in recommended use conditions and provide an appropriate power source for Nucleus Sound Processors.
The Nucleus 5 (CI500 series) Implant and Nucleus Freedom (CI24RE) Implant are safe at depths less than 40 m. (131 ft.), and Nucleus 22 and 24 Series are safe to 25 m. (81 ft.). Recipients should seek medical advice before participating in a dive for conditions that might make diving contraindicated (e.g., middle ear infection, etc.) When wearing a mask, avoid pressure over the implant site.
Recipients should not wear the sound processors while sleeping, as they may not have awareness of the processor becoming unusually warm or hot. Do not allow children or recipients with disabilities to wear their processor while sleeping.
When using retention aids such as the Snugfit™ or LiteWear, be aware that it may take longer to remove the processor if the processor becomes unusually warm or hot. Do not attach the LiteWear beneath layers of clothing.