title: Unilateral hippocampal sclerosis with contralateral temporal scalp ictal onset.
abstract: OBJECTIVE
  To investigate the clinical characteristics and surgical outcomes in patients with unilateral hippocampal sclerosis whose scalp ictal EEG recordings localize to the opposite temporal lobe.
  
  
  METHODS
  We retrospectively reviewed the data of all adult patients who had undergone depth electrode implantation for suspected temporal lobe epilepsy (TLE) at UCLA (1993-2000) or the Montreal Neurological Institute (1991-1998) to identify patients who had (a) unilateral hippocampal atrophy, and (b) surface ictal recordings in which the majority of seizures appeared to initiate in the opposite temporal lobe, with few or none that were concordant with the hippocampal atrophy.
  
  
  RESULTS
  Of 109 patients with suspected TLE who underwent depth electrode study at the two centers, five patients met the aforementioned criteria. Four of these five had very severe hippocampal atrophy, whereas the fifth had mild atrophy but extensive signal change on magnetic resonance imaging (MRI). Depth electrode recordings in four of the five patients yielded clear ictal onset in the mesial temporal lobe ipsilateral to the imaging abnormality (contralateral to apparent scalp ictal onset). One patient had an unusual bitemporal onset pattern, which was nonetheless suggestive of onset in the sclerotic hippocampus. No patient had intracranial ictal onset contralateral to the imaging abnormality. All patients underwent resection of the structurally abnormal temporal lobe. After follow-up of > or = 2 years, four (80%) of five patients were seizure free, while the fifth showed lesser improvement (class III).
  
  
  CONCLUSIONS
  Some patients with severe hippocampal sclerosis (sometimes called a "burned-out hippocampus") have atypical spread of ictal discharges, resulting in apparent gross discordance between imaging and scalp ictal recordings. These patients nonetheless have excellent surgical outcomes on the whole. Whether such patients may forego intracranial recordings requires further study.
authors.affiliation: Department of Neurology, Northwestern University Feinberg School of Medicine, Chicago, Illinois 60611, USA. scottmintzer@northwestern.edu
authors.forename: Scott
authors.initials: S
authors.lastname: Mintzer
authors.forename: Fernando
authors.initials: F
authors.lastname: Cendes
authors.forename: Jason
authors.initials: J
authors.lastname: Soss
authors.forename: Frederick
authors.initials: F
authors.lastname: Andermann
authors.forename: Jerome
authors.initials: J
authors.lastname: Engel
authors.forename: Francois
authors.initials: F
authors.lastname: Dubeau
authors.forename: Andre
authors.initials: A
authors.lastname: Olivier
authors.forename: Itzhak
authors.initials: I
authors.lastname: Fried
mesh_terms: D000328:Adult; D038481:Anterior Temporal Lobectomy; D004567:Electrodes, Implanted; D004569:Electroencephalography; D004833:Epilepsy, Temporal Lobe / Q000503:physiopathology* / Q000601:surgery; D005260:Female; D005500:Follow-Up Studies; D007839:Functional Laterality / Q000502:physiology*; D006624:Hippocampus / Q000473:pathology* / Q000503:physiopathology / Q000601:surgery; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D012598:Sclerosis; D013702:Temporal Lobe / Q000503:physiopathology* / Q000601:surgery; D016896:Treatment Outcome