MEG plays a crucial role in advanced epilepsy treatments. By measuring the magnetic fields produced by neuronal activity, MEG provides precise localization of epileptiform discharges, which identify regions of the brain where seizures originate. This high-resolution mapping enables physicians to develop targeted treatment plans that enhance the effectiveness of interventions. Beyond epileptiform discharge localization, MEG is used for functional mapping of the brain by identifying critical areas responsible for functions such as movement, speech, and sensory processing. By preserving these essential areas during surgical procedures, MEG ensures optimal patient outcomes.
Spike localization: Brain activity in patients with epilepsy often undergoes sporadic bumps or ‘spikes’. Spikes are a clue to where seizures originate, and by recording the minute magnetic fields associated with these spikes, MEG locates the seizure-producing areas in the brain. The pictures below show spikes in two different patients with epilepsy and the MEG localization of their spikes on the brain.
(Top) MEG/EEG tracings depicting a representative spike (gray bar). (Middle) Spike picked up by MEG sensors. (Bottom) Location of the spike (yellow triangle) over the patient’s brain MRI, identifying a seizure-producing area in the posterior portion of the middle of the left hemisphere.
MEG localization of spikes in three different clusters in a patient with epilepsy arising from a large portion of one hemisphere
Functional mapping: Brain activity in patients (as well as in healthy individuals) undergoes alteration during activities such as movement, sensation, vision, spoken speech or listening to sounds or words. MEG detects these alterations and localizes them in the brain, thus providing a ‘map’ of important brain areas for these functions. The pictures below show the location of brain activity over left and right hemispheres in a patient listening to spoken words.
Mapping of receptive language in a patient with epilepsy. Red circles indicate active brain areas while the patient listens to single spoken words.
MRI of a patient with epilepsy from the left hemisphere showing superimposition of spike and speech localization. The gap between the spikes (yellow triangles) and speech areas (red dots) confirmed that speech function was located at a significant distance away from seizure-producing areas. This allowed brain surgery to be planned that targeted the seizure areas and kept a safe distance from the patient’s speech brain areas.