Head and Brain MRI: What It Shows and How the Examination Is Performed

A hum, rhythmic clicking, a narrow tunnel, and a request not to move — that is what a head MRI feels like from the inside. For a person with a headache, it is primarily a way to find out what is happening inside, not a test of endurance. Let us sort out, without myths, what the examination shows and how to prepare for it.

Head MRI: what kind of examination this is

Magnetic resonance imaging is a method of obtaining images of internal organs and tissues using the phenomenon of nuclear magnetic resonance: the electromagnetic response of hydrogen nuclei in a strong magnetic field is measured. X-rays and ionizing radiation are not used — this is how MRI differs from computed tomography and positron emission tomography. The machine is a large device with a short tunnel and a flat table that slides inside; the examination is performed by a radiologic technologist, while the scanner is operated by a staff member from the adjacent room who maintains contact with you.

What a brain MRI shows

The method provides detailed images of the brain and nerve tissues. It is used to diagnose and monitor congenital defects, hemorrhages (subarachnoid, subdural, epidural, and within brain tissue), aneurysms, infections such as brain abscess, tumors — malignant and benign, hormonal disorders, multiple sclerosis, and stroke. A head MRI helps determine the cause of muscle weakness, numbness and tingling, changes in thinking or behavior, hearing loss, headaches when other symptoms are present, difficulty speaking, vision problems, and dementia. A separate type is magnetic resonance angiography, which shows the blood vessels of the brain. Abnormalities may reflect vascular anomalies, acoustic neuroma, bleeding, infection, edema, damage after trauma, hydrocephalus, loss of brain tissue, multiple sclerosis, stroke, or transient ischemic attack.

How a head and neck MRI is performed

You will be asked to lie down on the table and will be given earplugs or headphones — the scanner knocks and hums loudly. You need to lie still; sometimes you are asked to hold your breath. The procedure usually takes from 15 minutes to an hour, according to other data 30–60 minutes, sometimes longer. Before the scan, a contrast agent may be injected intravenously to better visualize certain areas. Preparation is simple:

• remove jewelry, watches, hearing aids, hairpins, and clothing with metal zippers;
• remove coins and keys from pockets and remove makeup;
• report pregnancy or breastfeeding, surgeries, kidney disease, metal implants, and allergy to contrast;
• check with your doctor whether you need to fast for 4–6 hours before the scan.

After a scan with contrast, you will be asked to wait about 30 minutes to rule out a reaction. Ask the clinic when the result will be ready: the images are interpreted by a radiologist and passed on to the referring doctor. If there is no response, contact the doctor who ordered the examination.

For which symptoms a brain MRI is ordered

A referral is given by a doctor when it is necessary to find the cause of complaints or to check how treatment is working. MRI is ordered for headaches when other symptoms are present. Discussion with a doctor is appropriate for numbness, weakness, changes in speech, hearing, or vision, and changes in thinking and behavior.

Head MRI and CT: what is the difference

CT is faster and is usually available directly in the emergency department, so it is preferred for acute head and facial trauma, hemorrhage in the first 24–48 hours, early symptoms of stroke, and diseases of the skull and ear bones. MRI is in many cases more sensitive to brain problems such as small lesions, but it is noisier and longer and requires staying still in the tunnel.

Limitations and contraindications for MRI

MRI is safe during pregnancy; side effects from magnetic fields and radio waves have not been registered to date. Strong magnets can disrupt the operation of a pacemaker and other implants, and metal inside the body may shift, so such details must be reported in advance. Gadolinium-based contrast is usually well tolerated but may be harmful to people with kidney disease on dialysis. Serious complications are rare; after the injection, bruising, nausea, rash, headache, a metallic taste, and dizziness are possible. If you fear confined spaces, tell the staff in advance.

An MRI referral in itself is not a reason to call an ambulance. Call 103 or 112 for signs of stroke or another life-threatening condition, and also if after contrast administration you develop difficulty breathing or swallowing, or fainting.

MRI is an informative but only a diagnostic tool; discuss the interpretation of the images and the decision on further steps with a doctor, not with forums.

This content is for reference and does not replace a doctor's consultation. Medical disclaimer