ABSTRACT
This chapter describes the use of magnetoencephalography (MEG) in the clinical assessment of brain activity in patients referred for presurgical mapping of eloquent cortex and the identification of zone(s) of interictal discharge in seizure disorders. Like electroencephalography (EEG), MEG measures electromagnetic activity. MEG sensors detect the neuromagnetic fields produced by current flow within neurons. Specifically, the neuromagnetic signals induce an electric current within the wire loops of a detection coil. The neuromagnetic field associated with a single postsynaptic event is too weak to produce a magnetic field that MEG sensors can detect. In most clinical cases, spontaneous electromagnetic activity is recorded to examine endogenous rhythmic activity as well as abnormal epileptiform discharges in patients with seizure disorders. One of the principal clinical applications of MEG is the detection and localization of interictal epileptiform activity in patients with seizure disorders, accomplished by simply recording spontaneous activity.
