title: Hippocampal and amygdala volumes in an older bipolar disorder sample.
abstract: BACKGROUND
  Brain volumetric magnetic resonance imaging (MRI) studies of adult bipolar disorder samples, compared with healthy controls, have reported conflicting results in hippocampal and amygdala volumes. Among these, few have studied older bipolar samples, which would allow for examination of the effects of greater duration in mood episodes on brain volumes. The aim of this study was to compare hippocampal and amygdala volumes in older bipolar patients with controls.
  
  
  METHODS
  High-resolution MRI scans were used to determine hippocampal and amygdala volumes that were manually traced using established protocols in 18 euthymic patients with DSM-IV bipolar I disorder (mean age 57 years) and 21 healthy controls (mean age 61 years). Analysis of covariance (ANCOVA) was used to explore group differences while controlling for intracranial volume (ICV), age, sex, and years of education.
  
  
  RESULTS
  While gray matter, white matter, and cerebrospinal fluid volumes did not differ between the groups, bipolar disorder patients had smaller ICV (t = 2.54, p = 0.015). After correcting for ICV, the bipolar group had smaller hippocampal (left hippocampus F = 13.944, p = 0.001; right hippocampus F = 10.976, p = 0.002; total hippocampus F = 13.566; p = 0.001) and right amygdala (F = 13.317, p = 0.001) volumes. Total hippocampal volume was negatively associated with the duration of depressive (r = -0.636; p = 0.035) and manic (r = -0.659; p = 0.027) episodes, but not lithium use. Amygdala volumes were not associated with the duration of mood episodes.
  
  
  CONCLUSIONS
  Older bipolar disorder patients had smaller hippocampal and amygdala volumes. That smaller hippocampal volume was associated with the duration of mood episodes may suggest a neuroprogressive course related to the severity of the disorder.
authors.affiliation: Euroa Centre, Prince of Wales Hospital, Sydney, Australia. Chanaka.Wijeratne@sesiahs.health.nsw.gov.au
authors.forename: Chanaka
authors.initials: C
authors.lastname: Wijeratne
authors.forename: Sonal
authors.initials: S
authors.lastname: Sachdev
authors.forename: Wei
authors.initials: W
authors.lastname: Wen
authors.forename: Olivier
authors.initials: O
authors.lastname: Piguet
authors.forename: Darren M
authors.initials: DM
authors.lastname: Lipnicki
authors.forename: Gin S
authors.initials: GS
authors.lastname: Malhi
authors.forename: Phillip B
authors.initials: PB
authors.lastname: Mitchell
authors.forename: Perminder S
authors.initials: PS
authors.lastname: Sachdev
mesh_terms: D000368:Aged; D000679:Amygdala / Q000473:pathology*; D001714:Bipolar Disorder / Q000473:pathology*; D016022:Case-Control Studies; D005260:Female; D006624:Hippocampus / Q000473:pathology*; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D059906:Neuroimaging; D009929:Organ Size