title: Hippocampal size anomalies in a community-based cohort with childhood-onset epilepsy.
abstract: OBJECTIVE
  Epidemiologic evidence suggests the natural history of refractory mesial temporal lobe epilepsy is complicated, yet little is known about the hippocampus from the nontertiary center perspective.
  
  
  METHODS
  In a community-based cohort, individuals with nonsyndromic focal epilepsy with onset <16 years and controls had research MRI scans. Hippocampal (HC) volumes were manually measured, corrected for total brain volume, and converted to Z scores (Z(HC)) based on the controls' values. Volumes in cases and controls were compared.
  
  
  RESULTS
  Average volumes were not significantly different in cases with unknown cause (n = 117) relative to controls (n = 63). The group with structural and other conditions (n = 23) had significantly smaller volumes. Asymmetry (larger/smaller HC) did not vary among the 3 groups. Hippocampal variances were significantly larger in each epilepsy group relative to controls. In the unknown cause group, 25 (21%) had extreme() values: 15 (13%) with Z(HC) >1.96; 10 (9%) with Z(HC) <-1.96. By contrast, 2/63 (3%) controls had extreme values (p = 0.001). Within the unknown cause group, temporal lobe epilepsy (TLE) cases were more likely to have extreme hippocampal volumes than non-TLE (31% vs 15%, p = 0.03). Extreme volumes were generally interpreted as normal visually. These anomalies were not associated with seizure remission or pharmacoresistance.
  
  
  CONCLUSIONS
  Classic mesial TLE with hippocampal sclerosis is an uncommon finding in the general population. Volume anomalies, both large and small, are often bilateral. The significance of these findings is unclear; however, speculations regarding preexisting hippocampal pathology (e.g., dysplasia) as a factor in TLE and other neocortical epilepsies have been made by others.
authors.affiliation: Department of Biology, Northern Illinois University, DeKalb, IL 60115, USA. atberg@niu.edu
authors.forename: A T
authors.initials: AT
authors.lastname: Berg
authors.forename: H R
authors.initials: HR
authors.lastname: Pardoe
authors.forename: R K
authors.initials: RK
authors.lastname: Fulbright
authors.forename: S U
authors.initials: SU
authors.lastname: Schuele
authors.forename: G D
authors.initials: GD
authors.lastname: Jackson
mesh_terms: D000293:Adolescent; D000328:Adult; D017668:Age of Onset; D002648:Child; D015331:Cohort Studies; D004833:Epilepsy, Temporal Lobe / Q000473:pathology*; D005260:Female; D006624:Hippocampus / Q000473:pathology*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D012044:Regression Analysis; D012111:Residence Characteristics; D055815:Young Adult