Short and middle-latency Median Nerve (MN) SEPs recorded by depth electrodes in human pre-SMA and SMA-proper

C. Barba, M. Valeriani, G. Colicchio, F. Mauguière

Research output: Contribution to journalArticle

Abstract

Objective: To 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. Methods: Short 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. Results: The 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. Conclusions: Among premotor areas, somatosensory inputs seem to reach pre-SMA and area 6 but not SMA-proper. Significance: This study assessed that no scalp SEP in the first 100 ms after MN stimulus could be generated in SMA-proper.

Original languageEnglish
Pages (from-to)2664-2674
Number of pages11
JournalClinical Neurophysiology
Volume116
Issue number11
DOIs
Publication statusPublished - Nov 2005

Keywords

  • Epilepsy surgery
  • Evoked potentials
  • Somatosensory system

ASJC Scopus subject areas

  • Clinical Neurology
  • Radiology Nuclear Medicine and imaging
  • Neurology
  • Sensory Systems
  • Physiology (medical)

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