title: The Role of Thalamus Versus Cortex in Epilepsy: Evidence from Human Ictal Centromedian Recordings in Patients Assessed for Deep Brain Stimulation.
abstract: BACKGROUND
  The onset of generalized seizures is a long debated subject in epilepsy. The relative roles of cortex and thalamus in initiating and maintaining the different seizure types are unclear.
  
  
  OBJECTIVE
  The purpose of the study is to estimate whether the cortex or the centromedian thalamic nucleus is leading in initiating and maintaining seizures in humans.
  
  
  METHODS
  We report human ictal recordings with simultaneous thalamic and cortical electrodes from three patients without anesthesia being assessed for deep brain stimulation (DBS). Patients 1 and 2 had idiopathic generalized epilepsy whereas patient 3 had frontal lobe epilepsy. Visual inspection was combined with nonlinear correlation analysis.
  
  
  RESULTS
  In patient 1, seizure onset was bilateral cortical and the belated onset of leading thalamic discharges was associated with an increase in rhythmicity of discharges, both in thalamus and cortex. In patient 2, we observed bilateral independent interictal discharges restricted to the thalamus. However, ictal onset was diffuse, with discharges larger in the cortex even though they were led by the thalamus. In patient 3, seizure onset was largely restricted to frontal structures, with belated lagging thalamic involvement.
  
  
  CONCLUSIONS
  In human generalized seizures, the thalamus may become involved early or late in the seizure but, once it becomes involved, it leads the cortex. In contrast, in human frontal seizures the thalamus gets involved late in the seizure and, once it becomes involved, it lags behind the cortex. In addition, the centromedian nucleus of the thalamus is capable of autonomous epileptogenesis as suggested by the presence of independent focal unilateral epileptiform discharges restricted to thalamic structures. The thalamus may also be responsible for maintaining the rhythmicity of ictal discharges.
authors.affiliation: 1 Department of Clinical Neurophysiology, Kingston Hospital NHS FT, London, UK.|2 Department of Clinical Neurophysiology, St George's University Hospitals NHS FT, London, UK.|3 Department of Basic and Clinical Neuroscience, King's College London, Institute of Psychiatry, Psychology and Neuroscience, London, UK.|4 Departamento de Fisiología, Facultad de Medicina, Universidad Complutense, Madrid, Spain.
authors.forename: David
authors.initials: D
authors.lastname: Martín-López
authors.affiliation: 3 Department of Basic and Clinical Neuroscience, King's College London, Institute of Psychiatry, Psychology and Neuroscience, London, UK.|5 Department of Clinical Neurophysiology, King's College Hospital NHS FT, London, UK.|6 Universidad San Francisco de Quito, School of Medicine, Quito, Ecuador.
authors.forename: Diego
authors.initials: D
authors.lastname: Jiménez-Jiménez
authors.affiliation: 7 Servicio de Neurofisiología Clínica Hospital Ramón y Cajal, Madrid, Spain.
authors.forename: Lidia
authors.initials: L
authors.lastname: Cabañés-Martínez
authors.affiliation: 8 Department of Neurosurgery, King's College Hospital NHS FT, London, UK.
authors.forename: Richard P
authors.initials: RP
authors.lastname: Selway
authors.affiliation: 3 Department of Basic and Clinical Neuroscience, King's College London, Institute of Psychiatry, Psychology and Neuroscience, London, UK.|4 Departamento de Fisiología, Facultad de Medicina, Universidad Complutense, Madrid, Spain.|5 Department of Clinical Neurophysiology, King's College Hospital NHS FT, London, UK.
authors.forename: Antonio
authors.initials: A
authors.lastname: Valentín
authors.affiliation: 3 Department of Basic and Clinical Neuroscience, King's College London, Institute of Psychiatry, Psychology and Neuroscience, London, UK.|4 Departamento de Fisiología, Facultad de Medicina, Universidad Complutense, Madrid, Spain.|5 Department of Clinical Neurophysiology, King's College Hospital NHS FT, London, UK.|9 Comprehensive Epilepsy Center Neuroscience Institute, Academic Health Systems, Hamad Medical Corporation, Doha, Qatar.
authors.forename: Gonzalo
authors.initials: G
authors.lastname: Alarcón
mesh_terms: D000328:Adult; D058256:Brain Waves / Q000502:physiology*; D002540:Cerebral Cortex / Q000503:physiopathology*; D046690:Deep Brain Stimulation / Q000379:methods*; D004569:Electroencephalography; D017034:Epilepsy, Frontal Lobe / Q000473:pathology / Q000503:physiopathology / Q000628:therapy; D004829:Epilepsy, Generalized / Q000473:pathology / Q000503:physiopathology / Q000628:therapy; D005260:Female; D006801:Humans; D008297:Male; D012189:Retrospective Studies; D013686:Telemetry; D013788:Thalamus / Q000503:physiopathology*; D014741:Video Recording; D055815:Young Adult
keywords: Intracranial EEG; centromedian nucleus; generalized epilepsy; ictal recordings