Article ID Journal Published Year Pages File Type
3048712 Clinical Neurophysiology 2005 11 Pages PDF
Abstract

ObjectiveTo analyse waveforms, latencies and amplitudes of Median Nerve (MN) SEPs recorded by stereotactically electrodes implanted in the SMA of 14 epileptic patients (9 in pre-SMA,3 in SMA-proper, 2 in both) in order to evaluate which short and middle-latency SEPs are generated in this area and which could be the physiological relevance of these responses.MethodsShort and middle-latency MN SEPs were recorded by chronically implanted electrodes in the fronto-temporal cortex and in particular in the mesial frontal region of 14 drug-resistant epileptic patients. MN stimulations of 100 μs were delivered by skin electrodes at the wrist; stimulus intensity was adjusted slightly above the motor threshold.ResultsThe main result of this study is that middle-latency SEPs were originated in pre-SMA but not in SMA-proper as demonstrated by both referential and bipolar recordings. In particular off-line computed bipolar traces between neighbouring contacts implanted in the pre-SMA and in the frontal external regions showed a phase reversal at the deepest contacts located in pre-SMA. Conversely, bipolar recordings between neighbouring contacts implanted in the SMA-proper and in the frontal external regions showed inversion recovery at more superficial contacts, implanted in area 6. Finally, we confirmed that no short-latency MN SEP (and in particular the N30) is originated in the whole SMA.ConclusionsAmong premotor areas, somatosensory inputs seem to reach pre-SMA and area 6 but not SMA-proper.SignificanceThis study assessed that no scalp SEP in the first 100 ms after MN stimulus could be generated in SMA-proper.

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