title: Mesial temporal lobe epilepsy with no specific histological abnormality: a distinct surgically remediable syndrome.
abstract: OBJECTIVE
  The purposes of the study were twofold: to clarify the clinical features and surgical outcome of mesial temporal lobe epilepsy (MTLE) with no specific histological abnormality and to determine the optimal surgical strategy.
  
  
  METHODS
  Twelve patients who met the following criteria were included: (1) normal preoperative MRI; (2) intracranial EEG findings consistent with mesial temporal onset of seizures; (3) selective amygdalohippocampectomy (AHE) was performed, and the patient was followed for more than 2years postoperatively; and (4) hippocampal histopathology was nonspecific. Clinical characteristics, intracranial EEG findings, and postoperative seizure outcome were examined. These twelve patients were compared with twenty-one patients with MTLE with unilateral hippocampal sclerosis (HS) on MRI who underwent intracranial EEG before resection (control group).
  
  
  RESULTS
  In patients with MTLE with no specific histological abnormality, the age at onset was significantly higher, the history of febrile seizures was significantly less frequent, and preoperative IQ score was significantly higher than that in the control group. The proportion of patients with bitemporal independent and/or nonlateralizing seizure onset on intracranial EEG was 50% in patients with MTLE with nonspecific histopathology and was significantly higher than that in the control group. Seizure outcome was classified as Engel class I in seven patients, class II in three, class III in one, and class IV in one. Seizure outcome was favorable even in three patients with seizures originating more frequently from the side contralateral to the resected side.
  
  
  CONCLUSIONS
  Mesial temporal lobe epilepsy with no specific histological abnormality is a clinical entity distinctly different from MTLE with HS. Bitemporal independent and/or nonlateralizing seizure onset on intracranial EEG is very common. Although the presence of lateral temporal and/or extratemporal epileptogenicity should always be kept in mind, postoperative seizure outcome after AHE is favorable even in cases with bitemporal independent and/or nonlateralizing seizure onset.
authors.affiliation: National Epilepsy Center, Shizuoka Institute of Epilepsy and Neurological Disorders, Urushiyama 886, Aoi-ku, Shizuoka 420-8688, Japan. Electronic address: n-usui@szec.hosp.go.jp.
authors.forename: Naotaka
authors.initials: N
authors.lastname: Usui
authors.forename: Koichi
authors.initials: K
authors.lastname: Baba
authors.forename: Kazumi
authors.initials: K
authors.lastname: Matsuda
authors.forename: Takayasu
authors.initials: T
authors.lastname: Tottori
authors.forename: Kiyohito
authors.initials: K
authors.lastname: Terada
authors.forename: Keiko
authors.initials: K
authors.lastname: Usui
authors.forename: Kunihiko
authors.initials: K
authors.lastname: Araki
authors.forename: Yasukiyo
authors.initials: Y
authors.lastname: Araki
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Hosoyama
authors.forename: Yushi
authors.initials: Y
authors.lastname: Inoue
authors.forename: Tadahiro
authors.initials: T
authors.lastname: Mihara
mesh_terms: D000293:Adolescent; D000328:Adult; D000679:Amygdala / Q000601:surgery*; D004569:Electroencephalography; D004833:Epilepsy, Temporal Lobe / Q000473:pathology* / Q000601:surgery*; D005260:Female; D007839:Functional Laterality; D006624:Hippocampus / Q000601:surgery*; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D018709:Statistics, Nonparametric; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome; D055815:Young Adult
keywords: Histopathology; Intracranial EEG; MRI; Mesial temporal lobe epilepsy; Seizure outcome; Selective amygdalohippocampectomy