Magnetic Source Imaging (MSI)
What is MSI?
Magnetic source imaging (MSI) is a noninvasive imaging tool used to locate abnormal brain activity, which can help determine the source of seizures. MSI also maps where important functions are controlled in the brain, like listening and talking.
How does MSI Work?
MSI uses two important technologies:
- Magnetoencephalography (MEG)
- Magnetic resonance imaging (MRI)
MEG measures subtle magnetic fields associated with the brain’s electrical currents. This can help to identify areas of seizure onset and to locate various brain functions. MRI completes the picture by showing brain structure. MSI refers to the combination of MEG and MRI.
Why get MSI?
MSI is often used as a pre-surgical evaluation tool for epilepsy and brain tumor patients. The service helps providers create successful surgery care plans for patients.
Tell your doctor if you have any of the following:
- Neurostimulators (RNS, DBS or VNS)
- Hearing aids
- Any other metal in your body (including some dental fillings)
Avoid wearing clothes that have metal, such as zippers, metal hooks, snaps or underwire bras.
Arrive without makeup or hair products.
Do not wear jewelry during the study.
Eat, drink, and take your medications as you normally would (unless told otherwise by your provider).
A technician will place removable markers on your head. Sensors may be placed on other areas of the body, including your arms or legs.
An MSI recording helmet will be placed on your head in order to record your brain’s electrical activity.
During the imaging, you will either lie down on your back, or you will be seated. You could be asked to perform tasks, such as looking at photos, listening to words, or doing hand motions.
How Long will the Sstudy Take?
The MSI study typically lasts 1 to 2.5 hours, but it may take up to 4. You are expected to remain as still as possible (unless instructed otherwise) – do not move your head or neck.
What if I have a Seizure during the Study?
If you have a seizure during the MSI study, providers will take proper safety precautions. They will ask you to remain as calm and still as possible. Additionally, EEG wires will be put on your head to record the seizure.
Will MSI Hurt?
MSI imaging is noninvasive and painless.