Magnetic source imaging as a tool for presurgical functional brain mapping.

This article describes magnetic source imaging, a newly-developing technology which can be used to noninvasively map eloquent cortex prior to surgical procedures. It is based on large-array detection of extracranial magnetic fields arising from neuronal currents evoked by peripheral stimulation. A range of evoked and spontaneous neuromagnetic activities are discussed along with clinical examples of the utility of the technique and comparison to other brain mapping techniques, such as positron emission tomography, functional magnetic resonance imaging, EEG, and ECoG.