In his role as president of the American Clinical MEG Society (ACMEGS), Jeff Tenney, MD, PhD, wants to help referring physicians see magnetoencephalography for what it is: an indispensable technology to directly measure and localize brain activity.

MEG has a unique ability to localize seizures, and extensive evidence supports its utility in presurgical epilepsy evaluations. However, unfamiliarity with the technology’s benefits and indications persists, even in the epilepsy community.

“Only MEG can measure fast, millisecond phenomena and also perform localization accurate to the millimeter level,” says Tenney, a pediatric epileptologist who is clinical director of the MEG Center at Cincinnati Children’s. “Based on the evaluation of several thousands of patients over the past several decades, MEG improves the surgical outcome of epilepsy patients. EEG and MEG go hand-in-hand in a comprehensive epilepsy surgery evaluation. Any patient who will undergo invasive EEG evaluation should have MEG completed prior to help guide the electrode placement.”

The non-invasive test measures the magnetic fields that naturally emanate whenever electric current flows within the neurons of the brain. The fields being measured are extremely weak, about a billion times smaller than the Earth's magnetic field. MEG’s sophisticated instrumentation is sensitive enough to detect these weak signals.

Cincinnati Children’s has been using MEG in the presurgical evaluation of epilepsy patients since 2005, with 135 evaluations last year alone.

A new MEG system, installed in 2020, provides a comfortable environment for a patient, whose head is fit inside a specialized helmet while lying on a bed for the duration of the test. Inside the helmet, 275 sensors detect abnormal brain activity and identify areas of the brain that are prone to seizures (in comparison, conventional EEG uses only about 20 sensors placed on the scalp).

Tenney and several of his ACMEGS colleagues published the 10 most common evidence-supported indications for MEG in epilepsy surgery (Journal of Clinical Neurophysiology, Nov. 2020). This resource for potential MEG users, current MEG referrers and newcomers to MEG provides guidance for routine clinical situations in which MEG can add unique, clinically valuable data to select surgical candidates. Examples include patients with “spikeless” EEGs and multiple lesions on MRI.

Only seven other pediatric institutions and 14 adult centers in the United States offer MEG, and Tenney hopes that number grows in the years to come. “At Cincinnati Children’s, we almost always use MEG in our presurgical evaluations for children with drug-resistant epilepsy, and about one-third of those patients are external referrals who come for the sole purpose of having the MEG study. The more physicians learn about what MEG can do, the more they realize its potential to localize seizure foci, which can lead to better surgical outcomes and help children with epilepsy experience an improved quality of life.”

The MEG Center is available to investigators throughout Cincinnati Children’s and the University of Cincinnati College of Medicine. Tenney has a current National Institutes of Health award to develop new MEG analysis methods for patients with epilepsy. The objective of this research is to use visual analysis and brain connectivity to pre-surgically distinguish between patients with epilepsy confined to the temporal lobe and those with a more extended seizure network. Tenney and his team hope these methods will improve presurgical planning of epilepsy and better identify patients at risk for worsened outcomes.