Editing Magnetoencephalography (section)

=== Focal epilepsy ===
The clinical uses of MEG are in detecting and localizing pathological activity in patients with [[epilepsy]], and in localizing [[eloquent cortex]] for surgical planning in patients with [[brain tumor]]s or intractable epilepsy. The goal of epilepsy surgery is to remove the epileptogenic tissue while sparing healthy brain areas.<ref>{{cite book | vauthors = Luders HO| title = Epilepsy Surgery|publisher=New York Raven Press|year=1992}}</ref> Knowing the exact position of essential brain regions (such as the [[primary motor cortex]] and [[primary sensory cortex]], [[visual cortex]], and areas involved in speech production and comprehension) helps to avoid surgically induced neurological deficits. Direct cortical stimulation and somatosensory evoked potentials recorded on [[electrocorticography]] (ECoG) are considered the gold standard for localizing essential brain regions. These procedures can be performed either intraoperatively or from chronically indwelling subdural grid electrodes. Both are invasive.

Noninvasive MEG localizations of the central sulcus obtained from somatosensory evoked magnetic fields show strong agreement with these invasive recordings.<ref>{{cite journal | vauthors = Sutherling WW, Crandall PH, Darcey TM, Becker DP, Levesque MF, Barth DS | title = The magnetic and electric fields agree with intracranial localizations of somatosensory cortex | journal = Neurology | volume = 38 | issue = 11 | pages = 1705–14 | date = November 1988 | pmid = 3185905 | doi = 10.1212/WNL.38.11.1705 | s2cid = 8828767 }}</ref><ref>{{cite journal | vauthors = Rowley HA, Roberts TP | title = Functional localization by magnetoencephalography | journal = Neuroimaging Clinics of North America | volume = 5 | issue = 4 | pages = 695–710 | date = November 1995 | pmid = 8564291 }}</ref><ref>{{cite journal | vauthors = Gallen CC, Hirschkoff EC, Buchanan DS | title = Magnetoencephalography and magnetic source imaging. Capabilities and limitations | journal = Neuroimaging Clinics of North America | volume = 5 | issue = 2 | pages = 227–49 | date = May 1995 | pmid = 7640886 }}</ref> MEG studies assist in clarification of the functional organization of primary somatosensory cortex and to delineate the spatial extent of hand somatosensory cortex by stimulation of the individual digits. This agreement between invasive localization of cortical tissue and MEG recordings shows the effectiveness of MEG analysis and indicates that MEG may substitute invasive procedures in the future.