What is an MRI of the brain?
MRI stands for magnetic resonance imaging (MRI). MRI is a technique that is used to take extremely detailed pictures of the brain. An MRI machine works by using incredibly strong magnets to temporarily alter the movements of water molecules in the brain tissue. This leads these molecules to release radio waves; these waves are almost identical to those used by cell phones, car radios, and older televisions. The radio waves are emitted in a special pattern that allows incredibly sensitive detectors in the machine to create a picture of every single thing within the brain.
Why would a neurologist order an MRI of the brain?
A brain MRI is incredibly useful for diagnosing many neurological diseases. Almost every significant neurological condition leads to changes within the brain tissue. Since removing a piece of this tissue to study is incredibly risky, an MRI allows for similar information to be gathered without the risk of damaging the brain.
Since MRIs are expensive and take a long time to perform, they are often ordered after other tests fail to help make a diagnosis or if a diagnosis is made but needs to be confirmed. Some of the symptoms that may lead a neurologist to consider an MRI are:
- Stroke symptoms such as sudden weakness of one part of the body or drooping of the face
- A new diagnosis of seizures
- A brain tumor seen on other brain scans such as a CT scan
- Chronic symptoms of weakness or fatigue that have no other clear cause
- Sudden changes in memory or behavior in the elderly
How long does an MRI of the brain take?
While there are several types of brain MRI. The most common type takes 3-4 hours. During this time, you will need to lie completely still and will have a detector close to your face. Some patients are able to complete this process without difficulty, others may need medications to help with discomfort or claustrophobia. Young children often require sedation, where medications are given that make them extremely sleepy while still being able to breathe normally.
There are some forms of MRI that take longer and some that only take a few minutes. These specialized types are not a replacement for a traditional MRI and are only appropriate in very specific circumstances.
What is the difference between a head MRI and a brain MRI?
A full head MRI is rarer than a brain MRI. An MRI of the head looks at the nerves and tissues that surround the skull as well as the brain itself. This may be done if a neurologist suspects that there are issues with the inner ears, nerves that run to the face, or blood vessels that sit just outside of the skull.
Which is better - an MRI or a CT scan for the brain?
An MRI and a CT scan have unique uses; while a brain MRI provides more detail, it may not always be appropriate.
- A CT scan is very effective at diagnosing bleeding inside the brain and damage to the bones of the skull. Waiting for an MRI in these situations is dangerous as treatments need to be started quickly.
- A CT scan can also look for blockages of the blood vessels in patients that may be having a stroke. This allows rapid treatment that would be impossible if neurologists waited for an MRI.
In some cases the greater detail provided by an MRI is essential.
- Looking for a cause of seizures requires detail that a CT scan cannot provide.
- Planning for surgical procedures on the brain, such as those required to remove a brain tumor, also require the detail provided by MRI.
- Diagnosing diseases such as multiple sclerosis, Alzheimer’s, Parkinson’s, and other neurological diseases that commonly occur in the elderly requires a high amount of detail only found in specialized MRI scans.
What are the side effects of brain MRI?
The side effects of MRI are almost nonexistent. The strong magnetic field that is used to create the MRI images does not lead to any changes in the brain. The human body is extremely resistant to magnetic fields; they do not cause harm in the way that radiation does.
Sometimes an injection known as gadolinium contrast is used during an MRI. This allows for greater detail in the images that the MRI produces. In rare cases, allergic reactions to this contrast may occur. This is very uncommon and can be easily treated by the doctors that are performing the MRI.
Is an MRI harmful?
MRI has no harmful effects on the brain or body with the exception of some rare reactions to contrast that are easily treated. The greatest risk of MRI is the strong magnet attracting certain types of metal in the body. Your neurologist will complete a detailed checklist to rule out this risk. Some types of metal and medical implants are MRI safe, as well as many pacemakers, cardiac stents, artificial joints, and other medical devices. Your physician will ensure that any devices you have are MRI safe prior to ordering an MRI.
