A CT IAM (Internal Auditory Meatus) scan uses X-rays and advanced computer processing to generate detailed, cross-sectional images of the temporal bones and the inner ear structures.
Doctors request this scan to investigate the bony causes of hearing loss, ringing in the ears, or severe dizziness.
While an MRI is often the go-to test for looking directly at the nerves in this area, a CT scan is the absolute best test for examining the intricate bones housing those nerves.
Common Indications for CT IAM
Your doctor may request a CT IAM for:
- Evaluating conductive or sensorineural hearing loss.
- Investigating persistent ringing in the ears (tinnitus).
- Diagnosing the cause of severe dizziness or vertigo.
- Assessing temporal bone fractures after a head injury.
- Surgical planning, such as mapping out the anatomy before a cochlear implant procedure.
What does the CT scanner look like?
It is a large, wide ring-shaped machine. You will lie on a narrow bed that glides your head into the center of the ring.
What happens during a CT IAM scan?
- You will lie flat on your back with your head resting in a special cradle to keep it perfectly still.
- Soft cushions may be placed next to your ears, and a light strap might be placed across your forehead to prevent any accidental movement.
- You will be asked to hold your breath for just a few seconds while the machine quickly captures the images.
Do I need to prepare for a CT IAM scan?
Usually, no special preparation is required.
Can I eat or drink before my CT IAM scan?
Yes. You can eat and drink normally prior to this exam, as contrast dye is rarely used for the CT version of this test.
How long does a CT IAM scan take?
Because the area being scanned is so small, the images are captured very quickly. The actual scanning time is often less than 5 minutes.
Why might contrast be needed?
Most CT IAM scans are done without contrast because doctors are primarily looking at the bone. If they need to see the soft nerves or blood vessels, they will typically order an MRI instead.
Is a CT IAM safe?
The scan uses ionising radiation focused on the temporal bones. Dose depends on the scanner and protocol, so the field and exposure should be limited to what is needed for the clinical question.
Pregnancy Precaution
Tell the clinician and CT team if you are pregnant or could be pregnant. Because the pelvis is outside the beam, fetal exposure from a correctly performed IAM CT is expected to be very low. The examination should still be justified and optimised, and MRI may be better for some nerve or soft-tissue questions.
Will the scan hurt?
The scan itself does not usually hurt, although keeping the head still or lying with an existing injury may be uncomfortable.
Will I need to remove anything before the scan?
You must remove all metal near your head and neck. This includes earrings, necklaces, hairpins, hearing aids, and metal dentures, as they will cause bright flares on the images.
What happens after the scan?
You can get up and continue with your normal daily activities right away.
Questions to ask your team
- Is CT assessing the temporal bone, trauma, infection, or another bony-ear problem?
- Would MRI be better for the hearing and balance nerves or other soft tissues?
- Will IV contrast be needed, and are pregnancy or previous scans relevant?
Sources and further reading
Conclusion
A CT IAM is a remarkably fast, painless way to evaluate the complex bones surrounding your inner ear. It helps doctors pinpoint the structural causes of hearing and balance issues, ensuring you get the right care.