title: Absolute spike frequency predicts surgical outcome in TLE with unilateral hippocampal atrophy.
abstract: OBJECTIVE
  To assess the prognostic implications of both the absolute spike frequency over the affected temporal lobe and the relative spike distribution between the two temporal lobes (i.e., uni- vs bitemporal spike distribution) for postoperative seizure control in a series of consecutive patients with medically refractory mesial temporal lobe epilepsy (MTLE) and MRI evidence of unilateral hippocampal atrophy (HA).
  
  
  METHODS
  In this study we included 55 patients (26 women; 29 men) with medically refractory MTLE and unilateral HA on high resolution MRI who underwent a comprehensive noninvasive presurgical evaluation including prolonged video-EEG monitoring. Patients were classified both according to absolute interictal spike frequency and to relative spike distribution between the two temporal lobes as follows: first, we distinguished between patients with frequent spikes (>/=60 spikes/hour over the affected temporal lobe) and patients with nonfrequent spikes (<60 spikes/hour over the affected temporal lobe). Second, we categorized patients in a unitemporal group (>/=90% of spikes over the affected temporal lobe) and a bitemporal group (<90% of spikes over the affected temporal lobe). In all patients first-time epilepsy surgery was performed with a minimum postoperative follow-up of 1 year.
  
  
  RESULTS
  One year following surgery we found that only 4 of 14 patients (28.6%) in the frequent spikes group remained completely seizure free since surgery compared to 33 of 41 patients (80.5%) in the nonfrequent spikes group (p = 0.001). Relative spike distribution did not show any significant implication for postoperative outcome.
  
  
  CONCLUSIONS
  This study identified absolute preoperative spike frequency as a strong predictor for surgical outcome, while relative spike distribution had no significant influence on postoperative seizure control.
authors.affiliation: 2nd Neurological Department, General Hospital Hietzing with Neurological Center Rosenhuegel, Vienna, Australia.
authors.forename: R
authors.initials: R
authors.lastname: Krendl
authors.forename: S
authors.initials: S
authors.lastname: Lurger
authors.forename: C
authors.initials: C
authors.lastname: Baumgartner
mesh_terms: D000200:Action Potentials; D000328:Adult; D001284:Atrophy; D004569:Electroencephalography; D004833:Epilepsy, Temporal Lobe / Q000473:pathology / Q000503:physiopathology* / Q000601:surgery*; D005260:Female; D006624:Hippocampus / Q000473:pathology* / Q000601:surgery; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D019635:Neurosurgical Procedures; D011184:Postoperative Period; D011237:Predictive Value of Tests; D013702:Temporal Lobe / Q000503:physiopathology / Q000601:surgery; D016896:Treatment Outcome; D014741:Video Recording