Specialist diagnostic testing
Magnetoencephalography (MEG)
MEG records the very small magnetic fields produced by electrical activity in the brain. It can add useful information during a detailed epilepsy assessment.
About this information
This webpage is subject to continuous review by Epilepsy Ontario to help keep the information current. This material is for informational purposes only and should not be used for self-diagnosis or as a substitute for professional medical advice, diagnosis, or treatment. Consult your healthcare provider about your own health and care.
Why might MEG be recommended?
MEG may help the specialist team identify where epileptic activity is occurring. It can also help map important functions when planning treatment, including possible surgery.
It is a specialized test, not something every person with epilepsy needs.
Recording brain activity
Sensitive equipment detects tiny magnetic signals generated by the brain. MEG does not use ionizing radiation.
Combining information
MEG findings can be combined with MRI images to relate activity to the brain’s structure. This is often called magnetic source imaging, or MSI.
MEG contributes to a bigger picture. Its findings are considered alongside EEG, MRI, seizure descriptions, and other assessments. A MEG result alone does not determine whether surgery is appropriate.
Before your appointment
- Follow the testing centre’s instructions about sleep, food, drink, and medication.
- Ask whether you need clean hair without styling products.
- Tell the team about implants, dental work, metal fragments, and removable metal items.
- Discuss difficulty keeping still, anxiety, or sensory needs.
- Ask about the full appointment length and transportation arrangements.
Do not stop medication or change your sleep schedule unless instructed. Some MEG protocols involve sleep changes or sedation; others do not.
During the test
You sit or lie with your head positioned near the sensors. Testing takes place in a specially shielded room to reduce interference from outside magnetic signals.
The team may record resting or sleeping activity. For some assessments, you may perform tasks involving movement, sensation, or language. EEG may be recorded at the same time.
Remaining still helps the team obtain useful recordings. Tell staff if you need a break or feel uncomfortable.
After the test
If no sedation was used, you can usually leave after the appointment according to the centre’s instructions. If sedation or sleep deprivation was involved, follow the specific recovery and travel guidance.
The recordings require specialist processing and interpretation. Ask when the report will be available and who will discuss it with you.
Questions to ask
- What question is MEG intended to answer in my assessment?
- Will EEG or MRI also be performed?
- Will I need sleep changes or sedation?
- How could the findings affect the next step in my care?
