Somatosensory, auditory, and visual evoked magnetic fields in patients with brain diseases

The features of somatosensory (SEFs), auditory (AEFs), and visual evoked fi elds (VEFs) in healthy subjects and patients with brain diseases provide th e basis for clinical investigations using magnetoencephalography (MEG). The SEFs provide clinically useful information to identify the central sulcus and somatotopic organization of the primary somatosensory cortex. Localizat ion accuracy of the SEFs can be tested by cortical stimulation during surge ry. Functional reorganization suggested by SEF studies must be verified by other modalities. The AEFs can localize the auditory cortex in the bilatera l temporal lobes. Separation of bilateral activities is much clearer in AEF s than in auditory evoked potentials. Modulation of the interhemispheric di fferences of latency, amplitude, and source localization of AEFs can be use d to evaluate auditory function in patients with intracranial lesions. Patt ern reversal VEFs provide stable localization of the primary visual functio n. Separation of bihemispherical activities is the advantage of VEFs over v isual evoked potentials. Investigation of VEFs provides objective evaluatio n of visual field deficits such as homonymous or bitemporal hemianopsia in patients with intracranial lesions. Evoked magnetic fields can provide usef ul diagnostic information. Such clinical findings, in turn, provides the op portunity to test the source estimation accuracy of MEG.