What is a head MRI?
Magnetic resonance imaging (MRI) of the head is a painless, noninvasive test that produces detailed images of your brain and brain stem. An MRI machine creates the images using a magnetic field and radio waves. This test is also known as a brain MRI or a cranial MRI.
An MRI scan combines images to create a 3-D picture of your internal structures, so it’s more effective than other scans at detecting abnormalities in small structures of the brain such as the pituitary gland and brain stem. Sometimes a contrast agent, or dye, can be given through an intravenous (IV) line to better visualize certain structures or abnormalities.
Why do I need a head MRI?
A head MRI is a useful tool for detecting a number of brain conditions, including:
- aneurysms, or bulging in the blood vessels of the brain
- multiple sclerosis
- spinal cord injuries
- hydrocephalus, a buildup of spinal fluid in the brain cavities
- hemorrhage, or bleeding
- problems with development or structure (such as a Chiari malformation)
- blood vessel issues
A head MRI can help determine whether you sustained any damage from a stroke or head injury. Your doctor may also order a head MRI to investigate symptoms such as:
- changes in thinking or behavior
- blurry vision
- chronic headaches
These symptoms may be due to a brain issue, which an MRI scan can help detect.
Additionally, there is a type of MRI called magnetic resonance angiography (MRA), which better examines the blood vessels in the brain.
How do I prepare for a head MRI?
The medical staff will need to know if you have any metal in your body, including:
- inner ear implants
- artificial joints
- a defibrillator or pacemaker
- particular types of heart valves
- vascular stents
- brain aneurysm clips
- metal shrapnel
- pain pumps
- diabetic pumps
If you’re wearing anything that contains metal, including jewelry or sunglasses, you will need to remove those items. Metal interferes with the MRI machine’s ability to produce a clear image. Braces and dental fillings typically won’t pose a problem, but pocketknives, pens, pins, and certain dental appliances can interfere. The staff may ask you to wear a hospital gown or clothing that doesn’t contain metal fasteners. You can’t have electronic devices in the MRI room.
Tell the medical staff if you’re pregnant. An MRI’s magnetic field affects unborn children in a way that isn’t yet fully understood.
Additionally, it’s important to let the staff know if you are claustrophobic. If so, you might need to take sedatives during the exam or have an “open” MRI. Open MRI machines have wider tunnels, which tend to be more tolerable for claustrophobic patients.
How is an MRI performed?
During the exam, it’s important to stay still to obtain the clearest images.
You will lie down on a table that slides into the MRI machine. The table slides through a large magnet shaped like a tube. You may have a plastic coil placed around your head. After the table slides into the machine, a technologist will take several pictures of your brain, each of which will take a few minutes. There will be a microphone in the machine that allows you to communicate with staff.
The test normally takes 30 to 60 minutes. You may receive a contrast solution, usually gadolinium, through an IV to allow the MRI machine to see certain parts of your brain more easily, particularly your blood vessels. The MRI scanner will make loud banging noises during the procedure. You may be offered earplugs or headphones to block the MRI machine’s noises.
There are no risks associated with an MRI itself. There is a very slight chance that you will have an allergic reaction to a contrast solution. Tell the medical staff if you have decreased kidney function. It may not be safe to use contrast solution if this is the case.
Women shouldn’t breastfeed 24 to 48 hours after they’ve been given contrast dye. They need to wait for the dye to leave their bodies.
What happens after a head MRI?
After the test, you can get dressed and leave the testing facility. If you were sedated for the exam you will need to have someone with you, usually a friend or relative, to drive you afterwards.
A radiologist will analyze your MRI images and provide your doctor with the results. Next steps will depend on whether the results revealed anything unusual or discovered the cause of any abnormalities.