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Magnetic Resonance Imaging (MRIs) Scans and Cochlear Implants

Magnetic Resonance Imaging (MRIs) Scans and Cochlear Implants

One of the eligibility tests I had before my Cochlear Implant surgery 18 years ago was to have an MRI scan. A scan takes place in a large futuristic-looking tube, an MRI suite, that contains powerful magnets and uses radio waves to produce detailed images of the inside of the body. I had to lie inside for 45 minutes (1). It was all rather dull, and upon completion, I thought nothing more of it.

MRI scans are of two types, notably:-

  • 1.5 Tesla MRI scans which have a lesser magnetic field with smaller image detail results.

  • 3.0 Tesla MRI scans which have a higher magnetic field with higher definition images. Surgeons consider this to be the gold standard.

The benefits of MRI scans can be tenfold. They are used to examine almost any part of the body. The results are used to help diagnose conditions, plan treatments and assess how effective previous treatment has been.

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It’s confusing…

Today, as I read the Cochlear Implant Facebook forums, the subject of MRI scans is a constant source of discussion. As I delve further into this information, I feel unsettled and slightly disturbed. There's indecisiveness and sometimes confusion in these forums around the topic of MRIs. I realise that having an MRI scan with a Cochlear Implant is complicated and not entirely risk-free.

I cast my mind back to the discussions I had with my Cochlear Implant Surgeon so long ago. Indeed, my conversations with him at the time were limited. I struggled to hear him, and my friend would try to write things down for me in translation. Would it have made a difference if he had explained to me how future MRI scans might be affected by having a Cochlear Implant? When it came to signing a document agreeing to Cochlear Implant surgery, I barely looked at it. I was desperate and wanted this so badly that I signed on the dotted line instantly.

Three main points…

In writing this article, I've tried to simplify what having an MRI scan means to a Cochlear Implant user. I've noticed that there are three main points which dominate the forum discussions, notably:-

(1) Head and neck scans

The presence of the Cochlear Implant magnet can compromise head and neck scans. It is because the magnet affects the scan causing the MRI to have a shadow (artefact). It can hinder the interpretation of the results.

You'd think that the ideal scenario is for a Surgeon to recommend the surgical procedure of magnet removal and consequent reinsertion. But, there can be a risk of local infection at the implant site. Also, not all Cochlear Implant models allow magnet removal, and with some models, magnet removal is a complicated surgical procedure due to poor design.

The above issues can place some Cochlear Implant recipients at a significant disadvantage.

I've seen some pictures of magnet removal, and it looks quite gruesome. But, in its defence, the procedure itself is not undertaken unless it's achievable and the risk is minimal. A Surgeon makes a small incision over the receiver/stimulator behind the ear and removes the magnet. A sterile bandage covers the incision. Once the MRI is complete, then the magnet is replaced and the incision closed.

It's reassuring to know that this kind of procedure dates back to the year 2000. In 2013, a report on Magnet Removal and Reinsertion in a Cochlear Implant Recipient Undergoing Brain MRI (2) looked at a 33-year-old female who had received a Freedom Contour Nucleus device in the year 2000. Eight years after her Cochlear Implant, she needed an MRI scan in the head. The magnet was removed and then replaced. The function of the device was not altered by the MRI nor by the surgical procedure.

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(2) General MRI scans at 1.5 Tesla MRI level

These scans do not usually require magnet removal. They can sometimes be problematic for older Cochlear Implant recipients (those recipients who don't have the most recent Cochlear Implant devices, namely the Advanced Bionics HiRes Ultra 3D, the MED-EL Synchrony and the Nucleus Profile Plus).

Should a general MRI scan be recommended for older Cochlear Implant recipients, then it will be at 1.5 Tesla MRI level using the bandage and splint method. Use a flat-plastic splint against the skin over the implant magnet site, and an elasticised compression bandage to secure it. Apply surgical tape for securing the bandage and splint in place.

This method is used to minimise the risk of MRI magnetic fields, generating potentially harmful forces. However, there have been incidents whereby recipients have experienced factors such as pain, dislodgement/migration of the magnet and demagnetisation of the magnet (3). This evidence highlights that not all Cochlear Implants are MRI friendly.

(3) General MRI scans at 3.0 Tesla MRI level (magnet removal recommendation)

A 1.5 Tesla MRI scan may not provide hospital professionals with enough detail. A 3.0 Tesla MRI scan recommendation may then require magnet removal in older Cochlear Implant Recipients.

Conclusion

To their credit, all three Cochlear Implant manufacturers now have Cochlear Implants on the market, mentioned previously, which allows general 3.0 MRI scans without problems.

Reassuringly, there are alternatives to MRI scans. The company 'Cochlear' in their promotional material refer to a study in which 85% of radiology professionals agree that they have an alternative diagnostic tool for patients who cannot undergo an MRI scan due to having a device or implant with a magnet (4).

It's clear, from the evidence, that not all Cochlear Implants are MRI friendly. If a recipient has the recommendation to have their magnet removed or to have an MRI scan, then there are risks. It's therefore essential that hospital professionals collate as much information as possible about a recipient's Cochlear Implant such as the model type, the year of the design and whether magnet removal is achievable. This data will aid preparation extensively. Also, should an MRI scan take place, then it's essential that this is real-time monitored by an MRI Specialist for safety purposes. By minimising risk, Cochlear Implant recipients will feel reassured.

Recommendations

  • Older Cochlear Implant recipients should avoid having an MRI scan unless it's critical to a diagnosis that cannot be made using other imaging means.

  • Safety precautions to minimise risk are essential for older Cochlear Implant recipients requiring an MRI scan. Documentation should be available to the MRI Specialist so that they can assess the Cochlear Implant model and make critical decisions. The Specialist also can do simple X-rays to have a clearer picture overall. For example, an X-ray of the skull (lateral view) can show the Cochlear Implant magnet location in more detail.

  • Prior to any MRI scan, Cochlear Implant users should remove their processor before entering an MRI suite. Medication is prescribed sometimes. Also, a safety button should be available to press should the procedure become unbearable. Throughout the scan, an MRI Specialist should monitor for any signs of unusual activity or magnet movement.

And finally…

  • If you are in the process of a magnet removal or an MRI scan, please do share this information with the appropriate professional/s.

  • Have your Patient Validation Card ready before any discussions with medical professionals. You can download this from Cochlear’s website. I also signed as a family member with Cochlear, and they sent me a plastic card which fits in my wallet. Advanced Bionics ensure that you receive a Patient Identification Card after your operation. A replacement card is also available by contacting them. MED-EL provides a Patient Identification Card. Please click here to download.

Footnotes

  1. An MRI scan lasts 15 to 90 minutes, depending on the size of the area scanned and the number of images/scans taken. Source: UK NHS website, https://www.nhs.uk/conditions/mri-scan/)

  2. Magnet Removal and Reinsertion in a Cochlear Implant Recipient Undergoing Brain MRI. Source: https://www.karger.com/Article/FullText/346239
    Authors: Migirov L. · Wolf M.

  3. PMC US National Library of Medicine. National Institutes of Health. MRI after Cochlear Implants. Source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6424707/

  4. Radiology Poll conducted by Penn, Schoen, Berland, August 2015. https://www.cochlear.com/a72c23e2-aa43-42b7-ad8c-cb73efd9c589/FUN2494-ISS1-SEP15-MRI-Infographic-Sheet.pdf?MOD=AJPERES&CONVERT_TO=url&CACHEID=a72c23e2-aa43-42b7-ad8c-cb73efd9c589

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