Dec. 18, 2024
For some children with epilepsy, surgical intervention becomes a crucial treatment pathway when medications fail to adequately control seizures. The approach to brain surgery for patients with focal epilepsy has been significantly enhanced by advancements in techniques like magnetoencephalography (MEG).
MEG is a noninvasive tool that precisely maps seizure-origin locations, facilitating targeted interventions for those with focal epilepsy. When integrated with other state-of-the-art, minimally invasive techniques such as MRI, fMRI, PET, SISCOM and EEG, MEG offers a powerful approach to optimize surgical planning, providing pediatric patients with intractable epilepsy the most sophisticated and personalized care available.
Clinical applications of MEG
MEG is a noninvasive technique that measures the magnetic fields generated by neuronal electrical activity. Using highly sensitive magnetic sensors cooled by liquid helium, MEG can provide precise localization of seizure onset zones with millisecond-level temporal resolution. Clinically, MEG is valuable for epilepsy localization and presurgical mapping of critical brain areas, complementing MRI and EEG.
"MEG is quite helpful for epilepsy surgical planning," says Keith Starnes, M.D., a pediatric neurologist at Mayo Clinic in Rochester, Minnesota. "It allows us to measure very small magnetic fields generated by the brain's electrical activity that can point toward the area of seizure onset."
Mayo Clinic Children's Center is one of a few places in the United States to routinely offer MEG. The technology records, analyzes and localizes minute magnetic fields produced by the brain's electrical currents. With the help of mathematical modeling, abnormal magnetic fields are then superimposed onto an MRI scan of the patient's brain to pinpoint the source of abnormal activity.
"MEG gives us an added function on top of the other things we do," says Kai J. Miller, M.D., Ph.D., a pediatric neurosurgeon at Mayo Clinic in Rochester, Minnesota. "Combining additional diagnostic information with MEG allows us to refine our approach and provide a clearer direction for our therapies."
Who is a candidate, and how does it work?
MEG is suitable for patients of all ages, and the procedure takes about two hours. The patient's head is placed in a helmet lined with hundreds of magnetic sensors. The patient lies still or completes a series of tasks, such as listening to words or looking at pictures. An EEG is recorded at the same time to help correlate the findings.
MEG is primarily used for patients with epilepsy who are considering surgery, but it can be beneficial for a number of situations. MEG is not unsafe for anyone, but because it is very sensitive to electromagnetic interference, good recordings aren't currently possible in patients with cochlear or certain types of programmable shunts. However, patients with metallic implants like neurostimulators or pacemakers are still good candidates for MEG.
MEG signals can be modeled onto a patient's own MRI in a 3D fashion, which can be helpful when planning further investigations. It also allows for a better characterization of patients with epilepsy, allowing for the most comprehensive battery of diagnostic tests and work-up than previously available.
Advantages of MEG
- Safe and noninvasive: MEG is noninvasive and safe for patients of all ages.
- High precision: By accurately locating seizure foci, MEG can help identify areas of the brain that might benefit from surgical resection or other interventions.
- No anatomical limitations: Unlike other imaging techniques, MEG is not impacted by anatomical differences.
- Added layer of information: Combining MEG with EEG helps create a clearer picture of the seizure dynamics.
Future applications and research
In looking toward the future, prioritizing improvements for patients keeps research at the forefront.
"There is plenty of MEG research ongoing, both within and outside of epilepsy," says Dr. Starnes. "We are currently planning research on expanding the types of functional mapping that we can do, which might prove beneficial for a wide range of patients. We are also looking at ways to use MEG data to better understand and tailor some of our therapies outside epilepsy surgery, like neuromodulation."
"We're always trying to push the envelope of helping patients move towards a higher percentage of seizure freedom," says Dr. Miller. "MEG is the kind of tool that allows us to advance our ability to deliver therapy at improved margins."
For more information
Refer a patient to Mayo Clinic.