title: Scalp, basal epidural and intravascular far-field recordings after median nerve stimulation: evidence for a separate N18a potential.
abstract: Far-field somatosensory evoked potentials (SSEPs) after median nerve stimulation were recorded from scalp- (Fz), epidural- (ED) and intravascular electrodes (basilar artery [Bas]) to study the nature of the controversial N18a component of the widespread N18 potential. In healthy volunteers frequently an N18a potential was recorded at Fz. Simultaneous Fz and ED recordings at the pontomesencephalic junction as well as Bas-recordings at the caudal basilar artery showed N18a components identical in latency and shape. With intravascular recordings the shapes differed between the top of the basilar artery and the caudal artery recordings. These findings support the existence of a separate N18a potential. The generator of the N18a is likely to be localized within the upper brainstem.
authors.affiliation: Department of Neurology, University of Mainz, Germany. koehler@neurologie.klinik.uni-mainz.de
authors.forename: J
authors.initials: J
authors.lastname: Koehler
authors.forename: R
authors.initials: R
authors.lastname: Besser
authors.forename: P
authors.initials: P
authors.lastname: Stoeter
authors.forename: P P
authors.initials: PP
authors.lastname: Urban
authors.forename: H C
authors.initials: HC
authors.lastname: Hopf
mesh_terms: D001165:Arteriovenous Malformations / Q000503:physiopathology; D001488:Basilar Artery; D001933:Brain Stem / Q000098:blood supply / Q000502:physiology*; D004558:Electric Stimulation; D004567:Electrodes, Implanted; D004824:Epidural Space; D004827:Epilepsy / Q000503:physiopathology; D005073:Evoked Potentials, Somatosensory / Q000502:physiology*; D006801:Humans; D008475:Median Nerve / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology; D012535:Scalp / Q000294:innervation