Cochlear Implants

Cochlear Implants
Cochlear implants are electronically-activated devices. Consequently, an MR procedure may be contraindicated for a patient with this type of implant because of the possibility of injuring the patient and/or altering or damaging the function of the device. In general, individuals with cochlear implants should be prevented from entering the MR environment unless specific guidelines exist to ensure safety for these devices.

Investigations have been conducted to determine if there are situations and specific conditions for a patient with a cochlear implant to safely undergo an MR procedure. These studies have resulted in highly specific guidelines that must be followed in order to safely perform MR examinations in patients with certain cochlear implants. Notably, some cochlear implants require the use of a 0.2-Tesla or 0.3-Tesla MR system, only, as part of the guidelines.

In other cases, the magnet associated with the cochlear implant may require removal prior to the MRI examination and the replacement following the scan. Additional MRI concerns include possible demagnetization of the internal magnet associated with the cochlear implant be exposure to the powerful static magnetic field of the MR system, as well as the substantial artifacts that exist if this magnet remains in place during an MRI examination. See specific information below.

HiRes 90K Implant and MRI (Advanced Bionics, Sylmar, CA)*

INFORMATION FOR MRI HEALTHCARE WORKERS
The HiRes 90K implant, with the internal magnet removed, has been tested with 1.5-Tesla/64-MHz and 0.3-Tesla/12-MHz MRI systems. MRI is contraindicated except under the circumstances described below.

Do not allow patients with a HiRes 90K cochlear implant to be in the area of an MRI system unless the following conditions have been met:
-The internal magnet must be surgically removed and replaced with the Magnet Insert Dummy before the patient undergoes an MRI procedure.
-The external sound processor and headpiece are removed before entering a room where an MRI scanner is located.
-MRI parameters should be selected to ensure a Specific Absorption Rate (SAR) of less than 1.0 W/kg in the head region.
-Continuous verbal and visual monitoring of the patient should be performed throughout the MRI procedure.

Image shadowing may extend as far as 7-cm squared area from the implant, resulting in loss of diagnostic information in the implant vicinity. The extent of the shadowing may be minimized by adjusting the signal parameters.

For additional information regarding the use of MRI with the HiRes 90K implant, please contact Advanced Bionics Technical Support.

Information for Patients
What is Magnetic Resonance Imaging? Magnetic resonance imaging (MRI) is a technique for taking remarkably clear and detailed pictures of internal organs and tissues using radio waves and a strong magnetic field.

When might a person be referred for an MRI? MRI is a sensitive exam for brain tumors, strokes, and certain chronic disorders of the nervous system such as multiple sclerosis. In addition, MRI might be recommended as a means of documenting disease of the cardiovascular system, pituitary gland, eye or inner ear.

Is the cochlear implant safe with MRI? Only after the magnet has been removed. As referrals for MRI are increasing, it is comforting to know that your implant is safe with this imaging technique. But you must be sure to have the magnet removed first.

The United States Food and Drug Administration (FDA) cleared the HiResolution Bionic Ear System’s HiRes 90K implant for Magnetic Resonance Imaging (MRI) at 0.3-Tesla and 1.5-Tesla with the internal magnet removed.

The magnetic and electrical properties of an MRI machine can potentially cause harm to a patient with a cochlear implant and damage the device. Therefore a patient with a cochlear implant should not be near an MRI machine, whether or not in use, unless the following conditions have been met:
-Internal magnet has been removed
-External processor and headpiece have been removed

A cochlear implant recipient should always consult with their implant surgeon before any imaging is performed, regardless of the imaging technique.

If an MRI is needed, what are the steps required to remove the magnet of the cochlear implant? Removing the magnet is a quick and easy procedure typically performed under local anesthesia. Your surgeon will shave a small area of hair directly over the implant. A small incision will be made exposing the implant. The magnet is gently removed and replaced with a sterilized insert. The incision is then closed. You may experience some swelling and slight discomfort following the procedure.

Will I be able to wear my processor after the magnet is removed? Once the incision has healed, you will be able to wear your processor. You should check with your implant center before resuming device use. Your audiologist will assist you in coupling the headpiece to the implant. Typically, a small hair clip is attached to hold the headpiece in place over the implant.

Can the magnet be replaced after an MRI? Yes, your surgeon can replace the magnet after an MRI is completed, provided that further MRI evaluations are not anticipated. Under local anesthesia, your surgeon will shave the hair over the implant and make a small incision. The sterilized insert is removed and replaced with a new sterilized magnet ordered from Advanced Bionics.

If necessary, can the HiResolution Bionic Ear System’s HiRes 90K be implanted without the magnet? Yes, your surgeon can elect to remove the magnet from the HiRes 90K before the device is implanted. In this case, the surgeon will order the sterilized insert with the device and replace the magnet with the sterilized insert at the time of surgery.

What recommendations should be provided to the radiologist/technologist when an MRI is ordered for a cochlear implant recipient? Your implant center can provide the MRI technologist or radiologist with the HiResolution Bionic Ear System’s HiRes 90K package insert. Further instructions are provided when the implant center orders the sterilized insert or replacement magnet from Advanced Bionics that can be forwarded to the MRI technologist as well.

Are other imaging techniques available? How is MRI different? There are many imaging techniques used today including x-rays, computed tomography (CT) scans, positron emission tomography (PET) scans, and ultrasound. MRI requires specialized equipment and expertise and allows evaluation of some body structures that may not be as visible with other imaging methods. Your medical team will discuss these options with you and determine which technique is optimal for your healthcare needs.

What do we need to do if we want to replace the magnet after the MRI? Provided additional MRIs are not anticipated, the center can order a sterilized “replacement magnet” CI-1412 from Advanced Bionics’ Customer Service. The replacement magnet will come with a surgical insert title “MRI for HiRes 90k implant” which provides detailed surgical instructions.

The Insert Dummy and Replacement Magnets are ordered SEPARATELY.

Can we implant the HiRes 90K without the magnet to begin with? Yes, order the Insert Dummy with the device. The surgical insert titled “MRI for HiRes 90K implant” that accompanies the insert dummy includes detailed surgical instructions for removing the magnet prior to implantation.

What specific recommendations can we provide the MRI technologist? The HiRes 90K implant is FDA approved for PRI testing at 0.3-Tesla and 1.5-Tesla with the magnet removed. The external hardware must also be removed before the patient enters the MRI testing room/suite. The center can provide the technologist with the “MRI for HiRes 90K implant” surgical insert that accompanies the insert dummy or replacement magnet.

[*Information provided with permission from Advanced Bionics, Sylmar, CA]

[MR healthcare professionals are advised to contact the manufacturer to ensure that the latest safety information is obtained and carefully followed in order to ensure patient safety relative to the use of an MR procedure.]

PULSAR COCHLEAR IMPLANT, PULSARCI100 COCHLEAR IMPLANT, MED-EL CORPORATION
The Pulsar Cochlear Implant, PULSARCI100 Cochlear Implant, MED-EL Corporation, Durham, NC) has the following information stated with regard to using MR imaging in patients with this device:

MRI Safe - Without Magnet Removal

Many cochlear implant users will require an MRI (Magnetic Resonance Imaging) scan at some point in their lifetime, so MRI compatibility is an important consideration when selecting a cochlear implant. MED-EL is the only cochlear implant manufacturer to offer MRI safety without surgical removal of the internal magnet. At MED-EL, we recognize the importance of providing access to critical medical treatment, including MRI, without disruption to your life or your hearing.

PULSARCI100 is MRI safe at 0.2-Tesla
• No need for surgery to remove and replace the internal magnet
• No incision or swelling to heal after an MRI scan
• No recovery time to affect implant use or performance
• No additional risk to the patient
• No significant impact on MRI image quality
• No limitations on daily activities following an MRI scan
• No risk of magnet displacement

[MR healthcare professionals are advised to contact the manufacturer to ensure that the latest safety information is obtained and carefully followed in order to ensure patient safety relative to the use of an MR procedure.]

MED-EL, CONCERT Cochlear Implant, MED-EL Corporation
Magnetic Resonance Imaging. MED-EL must be consulted prior to conducting a 0.2 Tesla (T) MRI examination on any patient having a MED‑EL CONCERT Device (www.medel.com)
-Do not, under any circumstance, scan a MED‑EL CONCERT patient with field strength greater than 0.2 T
-Scanning at 0.2-T, confirm that the patient is positioned with the magnetic field of the internal magnet in the same orientation as the magnetic field of the scanner. This is necessary to minimize torque on the internal magnet and induced voltage in the receiver.
-Note that there exist many types of 0.2 T MRI scanners. In some, the coil used for head imaging is attached to the MRI bed (i.e., the scanner table). Further counseling and recommendations will be provided to the cochlear implant professional and radiologist in the event of head imaging.
-Bilaterally implanted MED‑EL CONCERT patients, straight orientation of the head is acceptable

[MR healthcare professionals are advised to contact the manufacturer to ensure that the latest safety information is obtained and carefully followed in order to ensure patient safety relative to the use of an MR procedure.]

Nucleus 24 Series, Cochlear Implant (Cochlear Corporation)
Magnetic Resonance Imaging (MRI)

The Nucleus 24 cochlear implant and some Nucleus 22 cochlear implants have a removable magnet and specific design characteristics to enable it to withstand MRI up to 1.5 tesla, but not higher.

For patients with a Nucleus 22 cochlear implant without a removable magnet, MRI is contraindicated.

The Nucleus 24 cochlear implant has a removable magnet and specific design characteristics to enable it to withstand MRI up to 1.5 Tesla static field, a 64 MHz RF pulsed field, and pulsed gradient fields up to 20 Tesla/ sec. If the cochlear implant’s magnet is in place, it must be removed surgically before the patient undergoes a MRI procedure.

Magnetic Resonance Imaging (MRI) is contraindicated except under the circumstances described below. Patients with a cochlear implant should not enter a room where a MRI scanner is located except under the following special circumstances. The patient must remove the speech processor and headset before entering a room where a MRI scanner is located.

If the implant’s magnet is still in place, the implant may move, causing pain and/or tissue damage if the recipient is exposed to MRI. Once the magnet is surgically removed, the metal in the cochlear implant will affect the quality of the MRI, but no damage to the implant will occur. Image shadowing may extend as far as 6-cm from the implant, thereby resulting in loss of diagnostic information in the vicinity of the implant.

The MRI static field exerts a small force on the implant, even without the magnet. Without the magnet, the maximum force is less than the normal weight of the implant. This may be perceptible during the MRI procedure but is not harmful.

If there is doubt that the patient has a cochlear implant with a removable magnet, the physician should use an x-ray to check the radiopaque lettering on the implant. There are three platinum letters printed on each implant. If the middle letter is a “C”, “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.

Removing the Magnet
(when the patient needs a single MRI)
If an implant user develops a condition likely to require a single MRI examination, the magnet must be surgically removed. Surgery is usually performed under local anesthetic in a minor procedure room. A local injection of lidoocaine with 1:100,000 or 1:200,000 Epinephrine is used. The area over the magnet is shaved and the area is prepared for the incision. A curved incision is made posterior to the implant. The surgeon cuts through any fibrous growth around the implant to expose the magnet.

If a retaining suture runs across the magnet, the surgeon may bend the suture to expose the magnet. A dry sterile dressing is applied over the wound and the patient is taken for MRI examination. The recess may remain empty, with sterility maintained for a period of up to four hours. After the examination, a sterile magnet is replaced and the wound closed. A sterile dressing is applied overnight.

Magnet Removal
(when it is anticipated that the patient will need repeated MRIs in the future)
If it is anticipated that a patient will need repeated MRIs in the future, the surgeon may elect to remove the magnet on a more long-term basis. If it is known prior to implantation that the patient will need repeated MRIs in the future, the surgeon may elect to remove the magnet from the implant prior to implantation.

In these cases, the magnet may be removed and replaced with a non-magnetic titanium plug. The plug prevents the growth of fibrous tissue into the recess, which could make the future placement of a magnet difficult.

If the device has not yet been implanted, the magnet should be removed under sterile conditions. The cochlear implant is removed from its sterile packaging and placed on a flat stable surface with the magnet’s star symbol facing upward. The protective tubing should not be removed from the electrode array until implantation. Using an elevator, the lip of the silicone recess may be gently lifted in order to shell the magnet out of the recess. When removing the magnet, the pressure applied to the antenna of the implant should be minimized. If the device is already implanted, a similar method should be used to shell out the magnet while leaving the device in-situ. The sterile non-magnetic plug may then be inserted into the recess.

Replacing the Magnet
The magnet is replaced when there is no further need for MRI examinations. After exposure of the magnet recess, an elevator may be used to lift the lip of the recess and position the magnet. A sterile magnet should be inserted with the star symbol (denoting polarity) facing up. The wound is closed and a sterile dressing is applied.

Note to MR Healthcare Professionals: Different MRI guidelines exist for different countries. As such, use the appropriate information for your country. Visit www.Cochlear.com to obtain the proper information.

[MR healthcare professionals are advised to contact the respective manufacturer in order to obtain the latest safety information to ensure patient safety relative to the use of an MR procedure.]

REFERENCES
Chou H-K, McDougall JA, Can KW. Absence of radiofrequency heating from auditory implants during magnetic resonance imaging. Bioelectromagnetics 1995;16:307-316.

Deneuve S, Loundon N, et al. Cochlear implant magnet displacement during magnetic resonance imaging. Otol Neurotol. 2008;29:789-190.

Gubbels SP, McMenomey SO. Safety study of the Cochlear Nucleus 24 device with internal magnet in the 1.5 Tesla magnetic resonance imaging scanner. Laryngoscope. 2006;116:865-71.

Heller JW, et al. Evaluation of MRI compatibility of the modified nucleus multi-channel auditory brainstem and cochlear implants. Am J Otol 1996;17:724-729.

http://www.advancedbionics.comhttp://www.Cochlear.com

http://www.MEDEL.com

Majdani O, Rau TS, Gotz F, et al. Artifacts caused by cochlear implants with non-removable magnets in 3T MRI: phantom and cadaveric studies. Eur Arch Otorhinolaryngol. 2009;266:1885-90.

Majdani O, Leinung M, Rau T, et al. Demagnetization of cochlear implants and temperature changes in 3.0T MRI environment. Otolaryngol Head Neck Surg. 2008;139:833-9.

Ouayoun M, et al. Nuclear magnetic resonance and cochlear implant. Ann Otolaryngol Chir Cervicofac 1997;114:65-70.

Shellock FG. Magnetic Resonance Procedures: Health Effects and Safety. CRC Press, LLC, Boca Raton, FL, 2001.

Teissl C, Kremser C, Hochmair ES, Hochmair-Desoyer IJ. Cochlear implants: in vitro investigation of electromagnetic interference at MR imaging-compatibility and safety aspects. Radiology 1998;208:700-708.

Teissl C, Kremser C, Hochmair ES, Hochmair-Desoyer IJ. Magnetic resonance imaging and cochlear implants: compatibility and safety aspects. J Magn Reson Imaging 1999;9: