title: The long-term course of temporal lobe epilepsy: From unilateral to bilateral interictal epileptiform discharges in repeated video-EEG monitorings.
abstract: Bilateral interictal epileptiform discharges (IED) and ictal patterns are common in temporal lobe epilepsy (TLE) and have been associated with decreased chances of seizure freedom after epilepsy surgery. It is unclear whether secondary epileptogenesis, although demonstrated in experimental models, exists in humans and may account for progression of epilepsy.
  
  
  
  We reviewed consecutive video-EEG recordings from 1992 to 2014 repeated at least two years apart (mean interval 6.14years) in 100 people diagnosed with TLE.
  
  
  
  Ictal EEG patterns and IED remained restricted to one hemisphere in 36 people (group 1), 46 exhibited bilateral abnormalities from the first recording (group 2), 18 progressed from unilateral to bilateral EEG pathology over time (group 3). No significant differences between the three groups were seen with respect to age at epilepsy onset, duration, or underlying pathology. Extra-temporal IED during the first EEG recording were associated with an increased risk of developing bilateral epileptiform changes over time (hazard ratio 3.67; 95% CI 1.4, 9.4).
  
  
  
  Our findings provide some support of progression in TLE and raise the possibility of secondary epileptogenesis in humans. The development of an independent contra-lateral epileptogenic focus is known to be associated with a less favorable surgical outcome. We defined reliable EEG markers for an increased risk of progression to more widespread or independent bitemporal epileptogenicity at an early stage, thus allowing for individualized pre-surgical counselling.
authors.affiliation: NIHR University College London Hospitals Biomedical Research Centre, UCL Institute of Neurology, Queen Square, London WC1N 3BG, United Kingdom; Epilepsy Center, Department of Neurology, University Hospital Erlangen, Erlangen, Germany. Electronic address: Stephanie.gollwitzer@uk-erlangen.de.
authors.forename: Stephanie
authors.initials: S
authors.lastname: Gollwitzer
authors.affiliation: NIHR University College London Hospitals Biomedical Research Centre, UCL Institute of Neurology, Queen Square, London WC1N 3BG, United Kingdom.
authors.forename: Catherine A
authors.initials: CA
authors.lastname: Scott
authors.affiliation: NIHR University College London Hospitals Biomedical Research Centre, UCL Institute of Neurology, Queen Square, London WC1N 3BG, United Kingdom; Epilepsy Society, Chalfont St Peter SL9 0RJ, United Kingdom.
authors.forename: Fiona
authors.initials: F
authors.lastname: Farrell
authors.affiliation: NIHR University College London Hospitals Biomedical Research Centre, UCL Institute of Neurology, Queen Square, London WC1N 3BG, United Kingdom; Epilepsy Society, Chalfont St Peter SL9 0RJ, United Kingdom.
authors.forename: Gail S
authors.initials: GS
authors.lastname: Bell
authors.affiliation: NIHR University College London Hospitals Biomedical Research Centre, UCL Institute of Neurology, Queen Square, London WC1N 3BG, United Kingdom.
authors.forename: Jane
authors.initials: J
authors.lastname: de Tisi
authors.affiliation: NIHR University College London Hospitals Biomedical Research Centre, UCL Institute of Neurology, Queen Square, London WC1N 3BG, United Kingdom.
authors.forename: Matthew C
authors.initials: MC
authors.lastname: Walker
authors.affiliation: NIHR University College London Hospitals Biomedical Research Centre, UCL Institute of Neurology, Queen Square, London WC1N 3BG, United Kingdom.
authors.forename: Tim
authors.initials: T
authors.lastname: Wehner
authors.affiliation: NIHR University College London Hospitals Biomedical Research Centre, UCL Institute of Neurology, Queen Square, London WC1N 3BG, United Kingdom; Epilepsy Society, Chalfont St Peter SL9 0RJ, United Kingdom; Stichting Epilepsie Instellingen Nederland (SEIN), Heemstede, The Netherlands.
authors.forename: Josemir W
authors.initials: JW
authors.lastname: Sander
authors.affiliation: Epilepsy Center, Department of Neurology, University Hospital Erlangen, Erlangen, Germany.
authors.forename: Hajo M
authors.initials: HM
authors.lastname: Hamer
authors.affiliation: NIHR University College London Hospitals Biomedical Research Centre, UCL Institute of Neurology, Queen Square, London WC1N 3BG, United Kingdom.
authors.forename: Beate
authors.initials: B
authors.lastname: Diehl
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D018450:Disease Progression; D004569:Electroencephalography / Q000379:methods*; D004833:Epilepsy, Temporal Lobe / Q000473:pathology / Q000503:physiopathology* / Q000601:surgery; D005260:Female; D007839:Functional Laterality / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D013702:Temporal Lobe / Q000473:pathology / Q000503:physiopathology*; D055815:Young Adult
keywords: Electroencephalography; Focal epilepsy; Secondary epileptogenesis; Temporal lobe epilepsy