title: Dynamics of epileptic activity in a peculiar case of childhood absence epilepsy and correlation with thalamic levels of GABA.
abstract: OBJECTIVE
  Childhood absence epilepsy (CAE) is a syndrome with well-defined electroclinical features but unknown pathological basis. An increased thalamic tonic GABA inhibition has recently been discovered on animal models (Cope et al., 2009), but its relevance for human CAE is unproven.
  
  
  METHODS
  We studied an 11-year-old boy, presenting the typical clinical features of CAE, but spike-wave discharges (SWD) restricted to one hemisphere.
  
  
  RESULTS
  High-resolution EEG failed to demonstrate independent contralateral hemisphere epileptic activity. Consistently, simultaneous EEG-fMRI revealed the typical thalamic BOLD activation, associated with caudate and default mode network deactivation, but restricted to the hemisphere with SWD. Cortical BOLD activations were localized on the ipsilateral pars transverse. Magnetic resonance spectroscopy, using MEGA-PRESS, showed that the GABA/creatine ratio was 2.6 times higher in the hemisphere with SWD than in the unaffected one, reflecting a higher GABA concentration. Similar comparisons for the patient's occipital cortex and thalamus of a healthy volunteer yielded asymmetries below 25%.
  
  
  CONCLUSIONS
  In a clinical case of CAE with EEG and fMRI-BOLD manifestations restricted to one hemisphere, we found an associated increase in thalamic GABA concentration consistent with a role for this abnormality in human CAE.
authors.affiliation: Department of Neurophysiology, Centro Hospitalar Psiquiátrico de Lisboa, Lisbon, Portugal`
authors.forename: Alberto
authors.initials: A
authors.lastname: Leal
authors.affiliation: Department of Pediatric Neurology, Hospital Dona Estefânia, Lisbon, Portugal.
authors.forename: José P
authors.initials: JP
authors.lastname: Vieira
authors.affiliation: Faculty of Psychology and Educational Sciences, University of Coimbra, Coimbra, Portugal.
authors.forename: Ricardo
authors.initials: R
authors.lastname: Lopes
authors.affiliation: Instituto de Biofísica e Engenharia Biomédica, Faculdade de Ciências, Universidade de Lisboa, Lisbon, Portugal.
authors.forename: Rita G
authors.initials: RG
authors.lastname: Nunes
authors.affiliation: Institute of Biomedical Imaging and Life Sciences, Faculty of Medicine, University of Coimbra, Coimbra, Portugal.
authors.forename: Sónia I
authors.initials: SI
authors.lastname: Gonçalves
authors.affiliation: Center of Neuroscience, Swammerdam Institute for Life Sciences, University of Amsterdam, The Netherlands; Department of Bioengineering and Institute for Systems and Robotics (ISR/IST), LARSyS, Instituto Superior Técnico, Universidade de Lisboa, Portugal.
authors.forename: Fernando
authors.initials: F
authors.lastname: Lopes da Silva
authors.affiliation: Department of Bioengineering and Institute for Systems and Robotics (ISR/IST), LARSyS, Instituto Superior Técnico, Universidade de Lisboa, Portugal.
authors.forename: Patrícia
authors.initials: P
authors.lastname: Figueiredo
keywords: Childhood absence epilepsy; GABA; Human; Thalamus