About an IAM MRI scan
The internal auditory meatus (IAM) is a small canal in the bone at the side of the skull. It carries the nerves for hearing and balance (the vestibulocochlear nerve) and the facial nerve from the brain to the inner ear. An IAM MRI looks closely at both canals, the inner ears and the nearby part of the brain, using a strong magnetic field and radio waves rather than X-rays.
The scan is most often requested to look for an acoustic neuroma (also called a vestibular schwannoma), a slow-growing, non-cancerous growth on the hearing and balance nerve. It usually affects adults aged 30 to 60 and typically causes gradual hearing loss in one ear, tinnitus (ringing or other sounds in the ear) and sometimes dizziness or vertigo. An IAM MRI is usually considered when hearing loss or tinnitus affects one ear more than the other and no other cause is found on examination.
Most IAM scans are normal: acoustic neuromas are found in only a small proportion of people scanned, and the scan can also help rule out other causes. If a small acoustic neuroma is found, it is often monitored with repeat MRI scans rather than treated straight away.
What happens during the scan
You lie on your back on the scanner bed with your head in a head coil, a cage-like frame that sits around your head. You will be asked to remove hearing aids before going into the scanner room. The scanner is loud, so you will wear ear plugs or headphones, and the radiographer can talk to you throughout. You need to keep your head still. Very detailed pictures of the nerves can usually be taken without contrast dye; sometimes an injection of contrast (gadolinium) is used, which is charged separately.
What the scan can show
An IAM MRI can help to look at:
- acoustic neuroma (vestibular schwannoma)
- other growths near the inner ear, such as meningiomas
- the hearing, balance and facial nerves
- the inner ear structures (cochlea and semicircular canals)
- blood vessels pressing on the nerves
- inflammation and other changes near the inner ear and brainstem
An MRI shows structure, not how well you hear. It is usually done alongside hearing tests with an ENT specialist or audiologist.
Preparing for your scan
No special preparation is needed, and you can eat and drink normally. Bring the results of any hearing tests (audiograms) you have had, or upload them when you book, so the radiologist knows which ear is affected. You will need to remove hearing aids before the scan.
You can usually eat, drink and take your normal medicines unless the scanning centre tells you otherwise. Wear loose, comfortable clothing without metal zips or buttons, and leave jewellery at home. You will be asked to remove metal items such as hair clips, hearing aids, coins and keys, and you may be asked to change into a gown.
Before the scan you will complete a safety questionnaire. Tell the team if you have a pacemaker, any metal implant, surgical clips or other device, if you have kidney problems or allergies, or if you are, or might be, pregnant or breastfeeding. If you feel anxious in enclosed spaces, let us know when you book. Some centres can offer a relaxant, and if you take one you will need someone to take you home and must not drive for 24 hours.
Frequently asked questions
Why have I been sent for an IAM scan?
It is usually requested when hearing loss or tinnitus affects one ear more than the other, to rule out an acoustic neuroma. Most IAM scans are normal.
What is an acoustic neuroma?
An acoustic neuroma is a slow-growing, non-cancerous growth on the nerve used for hearing and balance. Small ones are often monitored with regular MRI scans; larger or growing ones may be treated with surgery or targeted radiotherapy.
Can I wear my hearing aids during the scan?
No. Hearing aids must be removed before you go into the scanner room. The radiographer will explain what will happen before you remove them and can communicate with you during the scan.
Do I need a referral?
You can tell us if you have a referral from your GP, physiotherapist or consultant and upload it when you book. If you do not have one, select “no referral” when you book and the scanning centre will confirm the next steps with you.
Sources
- NHS – Acoustic neuroma (vestibular schwannoma)
- Journal of Laryngology & Otology – Findings on 7,000 MRI scans of the internal auditory meatus
- MRI Master – MRI internal auditory meatus (IAMs) planning
- NHS – MRI scan
The information on this page has been gathered from various sources and is provided for general information only. It is not medical advice. TOP MRI is not liable for the accuracy or completeness of this information. Please speak to your doctor or the scanning centre about your own situation.