title: Single and paired-pulse electrical stimulation during invasive EEG recordings.
abstract: Invasive EEG recordings are frequently required during the presurgical exploration of patients with drug-resistant focal epilepsy in order to clarify the epileptic zone location. Intracranial direct electrical stimulations (DES) induce EEG and/or clinical responses that participate in this evaluation. Clinical DES protocols (1Hz and/or 50Hz) trigger massive cortical activation that can elicit seizures, after-discharges or complex clinical signs. In contrast, low-energy (<1Hz) protocols activate more localized cortical regions using single-pulse electrical stimulations (SPES). SPES can elicit two main types of responses. Cortico-cortical evoked potentials (CCEPs) correspond to highly consistent early responses, appearing before 100ms after stimulation, with fixed latency; they are considered physiological and assess the effective connectivity between the recorded regions. Late responses appear after 100ms; they are rare, inconsistent with variable latency and are suggestive of an underlying epileptogenic cortex. Paired-pulse stimulation paradigm associates a conditioning and a test stimulation to induce intracortical inhibition or facilitation by modifying the response amplitude. Largely used in transcranial magnetic stimulation, it has rarely been applied to CCEP although the mechanisms put in place seem highly similar. Low frequency intracerebral stimulations allow analysing brain connectivity and cortical excitability with a high temporal and spatial resolution. The development of new stimulation protocols and the combination with imaging or statistical techniques recently offered promising results.
authors.affiliation: Department of Functional Neurology and Epileptology, Hospices civils de Lyon, 59, boulevard Pinel, 69003 Lyon, France; Lyon's Research Neuroscience Center, Inserm U1028/CNRS UMPR 5292, CH Le Vinatier, Bâtiment 452, 95, boulevard Pinel, 69675 Bron, France.
authors.forename: S
authors.initials: S
authors.lastname: Boulogne
authors.affiliation: Department of clinical neurosciences, CHU Vaudois, 46, rue du Bugnon, 1011 Lausanne, Switzerland.
authors.forename: P
authors.initials: P
authors.lastname: Ryvlin
authors.affiliation: Department of Functional Neurology and Epileptology, Hospices civils de Lyon, 59, boulevard Pinel, 69003 Lyon, France; Lyon's Research Neuroscience Center, Inserm U1028/CNRS UMPR 5292, CH Le Vinatier, Bâtiment 452, 95, boulevard Pinel, 69675 Bron, France. Electronic address: sylvain.rheims@univ-lyon1.fr.
authors.forename: S
authors.initials: S
authors.lastname: Rheims
mesh_terms: D004558:Electric Stimulation / Q000379:methods*; D004569:Electroencephalography / Q000295:instrumentation* / Q000379:methods*; D004827:Epilepsy / Q000175:diagnosis* / Q000601:surgery; D006801:Humans; D019635:Neurosurgical Procedures
keywords: Cortical excitability; Direct electrical stimulation; Epilepsy surgery; Paired-pulse electrical stimulation; Single-pulse electrical stimulation