Quick answer: a brain MRI (also called a head MRI) uses a strong magnet and radio waves, not radiation, to take detailed pictures of the brain. It is the best imaging test for many brain conditions, including stroke, tumors, multiple sclerosis and the causes of seizures. It usually takes 30 to 60 minutes (30 to 45 without contrast). You lie on your back with your head inside a cage-like head coil, and you can usually eat, drink and take your medications as normal beforehand.
Brain scans are some of the most common MRIs I do, and they are also the ones that make patients most nervous, both about the tube and about what the scan might find. Here is what the test can show, how to prepare and what it feels like.
What does a brain MRI show?
MRI shows the brain in much more detail than other imaging methods, and it can see areas that bone hides on other tests. Doctors use it to investigate both sudden and long-standing symptoms. A brain MRI can help diagnose or monitor:
- stroke and damage from a previous stroke
- brain tumors
- multiple sclerosis and other chronic conditions
- causes of seizures (epilepsy)
- bleeding or damage from a head injury
- infections
- hydrocephalus, an enlargement of the fluid spaces inside the brain
- changes related to aging, such as loss of brain volume
- pituitary gland problems
- some eye and inner ear disorders
- developmental abnormalities
- problems with balance and movement control (ataxia)
A related scan, MR angiography (MRA), shows the blood vessels of the brain, often without contrast. It is sometimes added to a brain MRI.
An MRI shows structure, not a diagnosis by itself. Your doctor puts the images together with your symptoms and other tests.
Brain MRI with or without contrast?
Many brain MRIs are done without contrast. Contrast (gadolinium, given through an IV) is commonly added when the doctor is looking for or following tumors, infection, inflammation or multiple sclerosis activity. If contrast is used, the technologist takes a first set of images, injects it, and repeats some sequences. See [link: MRI With vs Without Contrast] for the risks and costs.
How to prepare for a brain MRI
- Food, drink and medications: for most brain MRIs, eat, drink and take your medications as usual unless your center tells you otherwise.
- Implants and metal: tell the team about any implant, device or metal in your body, especially aneurysm clips, cochlear implants, neurostimulators and pacemakers, and any metal near the eyes. See [link: Can You Have an MRI With Metal Implants, Tattoos or a Pacemaker?].
- Makeup, hair and jewelry: come without makeup, especially eye makeup, since some cosmetics contain metal particles that distort images of the face and brain. Avoid hair products and remove hairpins, clips, earrings and piercings.
- Dental work: fillings and braces are not a safety problem but can distort images near the face; mention them.
- Claustrophobia: your head will be fully inside the scanner, so if enclosed spaces worry you, plan ahead. See [link: Claustrophobic in an MRI? 12 Tips That Actually Help].
- Pregnancy and breastfeeding: tell the team. Non-contrast MRI is not known to harm a fetus, but non-urgent scans may be delayed until after delivery, and contrast is generally avoided in pregnancy. If you are breastfeeding, the American College of Radiology considers it safe to continue after contrast.
The full checklist is in [link: How to Prepare for an MRI].
What the scan feels like
- Positioning. You lie on your back and go into the scanner head first. Your head rests in a head coil, a plastic frame that fits around your head like a cage or helmet. It does not touch your face, and it is open in front of your eyes. Foam pads keep your head still and comfortable.
- Hearing protection. You get earplugs, headphones or both. Brain scans include some of the loudest sequences. See [link: Why Is an MRI So Loud?].
- The scan. Each sequence lasts from under a minute to several minutes. The most important thing is to keep your head completely still, including not swallowing hard or moving your jaw during a sequence if you can avoid it.
- Contrast, if needed. It is injected partway through, while you stay in place.
From the scanner room: [TU EXPERIENCIA: cómo es de verdad la colocación en la antena de cabeza, qué dices al paciente al cerrarla, si hay espejo para ver fuera, qué movimientos estropean más las imágenes cerebrales.]
How long does a brain MRI take?
Usually 30 to 60 minutes, or about 30 to 45 minutes without contrast. A limited «quick» brain MRI with only a few sequences can take less than 15 minutes. Plan extra time for check-in and changing. More detail in [link: How Long Does an MRI Take?].
Brain MRI vs CT scan
CT is faster and is often the first test in an emergency, such as a suspected stroke or head injury, mainly to look for bleeding. MRI shows the brain tissue in much more detail and does not use radiation, but it takes longer. Your doctor chooses based on the question and how urgent it is. See [link: CT Scan vs MRI].
Risks and limitations
- Very low risk for most people when safety screening is followed.
- Implants: the magnet can affect some devices or distort images near them.
- Contrast: allergic reactions are rare and usually mild. Tiny amounts of gadolinium can remain in the body after multiple contrast scans, with no known health effects, mostly relevant for people who need many scans over their lifetime.
- Movement: if you cannot stay still because of anxiety, confusion or pain, image quality suffers.
- Size: very large patients may not fit in some scanners, which have weight limits.
Getting your results
A radiologist, a doctor who specializes in reading imaging exams, reviews the images and sends a signed report to the doctor who ordered the scan, who will share the results with you. Brain MRI reports use technical language, and some findings sound alarming but are common and harmless, especially with age. Go over the report with your doctor before drawing conclusions. You may sometimes need a follow-up scan to check a finding over time.
Tips from the technologist
[TU EXPERIENCIA: 3-4 consejos propios para la RM cerebral. Ideas: ir sin maquillaje ni gomina, cerrar los ojos al entrar, tragar en las pausas entre secuencias, avisar de dolores de espalda o cuello para acolchar bien.]
Frequently asked questions
Does a brain MRI show everything?
No test shows everything. A brain MRI is very detailed for brain tissue, but some conditions are better seen with other tests, and many symptoms (such as most headaches) have no visible cause on an MRI.
Can a brain MRI detect dementia?
It can show changes such as loss of brain volume and rule out other causes of memory problems, like tumors or strokes. The diagnosis of dementia also depends on clinical evaluation and other tests.
Can I keep my eyes open during a brain MRI?
Yes, unless the technologist asks otherwise. Many people find it easier to keep them closed.
Do I need to remove my dentures or hearing aids?
Yes. Removable dental work and external hearing aids must be taken out before entering the scanner room.
Is a brain MRI safe?
Yes, for almost everyone. It uses no radiation, and the main precautions are about implants, metal and, if used, contrast.
This article is for general information and does not replace advice from your doctor or imaging team.