title: Memory impairment in out-of-hospital cardiac arrest survivors is associated with global reduction in brain volume, not focal hippocampal injury.
abstract: OBJECTIVE
  More than 30% of out-of-hospital cardiac arrest (OHCA) survivors suffer significant memory impairment. The hippocampus may be vulnerable to hypoxic injury during cardiac arrest. The purpose of this study was to determine whether selective hippocampal injury is the substrate for this memory impairment.
  
  
  METHODS
  Seventeen OHCA survivors and 12 patients with uncomplicated myocardial infarction were studied. OHCA survivors were divided into those with impaired and intact memory. Memory was assessed by use of the Rivermead Behavioural Memory Test and Doors and People Test. MRI was used to determine intracranial, whole-brain, amygdala-hippocampal complex, and temporal lobe volumes. Brain structure was also examined by statistical parametric mapping.
  
  
  RESULTS
  Left amygdala-hippocampal volume was reduced in memory-impaired OHCA victims compared with control subjects (mean 3. 93 cm(3) and 95% CI 3.50 to 4.36 cm(3) versus mean 4.65 cm(3) and 95% CI 4.37 to 4.93 cm(3); P=0.002). Left temporal lobe and whole-brain volumes were also reduced. There were no differences in amygdala-hippocampal volume indexed against ipsilateral temporal lobe volume. Significant correlations were observed between total brain volume and Rivermead Behavioural Memory Test (r=0.56, P<0.05) and Doors and People Test (r=0.67, P<0.01) scores in OHCA survivors. Both recall and recognition were compromised in memory-impaired subjects. Statistical parametric mapping did not detect focal brain abnormalities in these subjects. Global cerebral atrophy was confirmed by qualitative assessment.
  
  
  CONCLUSIONS
  Memory impairment in OHCA survivors is associated with global cerebral atrophy, not selective hippocampal damage. Rehabilitation protocols need to account for the global nature of the brain injury.
authors.affiliation: Cardiovascular Research, University of Edinburgh, Royal Infirmary of Edinburgh, Edinburgh, UK. N.Grubb@ed.ac.uk
authors.forename: N R
authors.initials: NR
authors.lastname: Grubb
authors.forename: K A
authors.initials: KA
authors.lastname: Fox
authors.forename: K
authors.initials: K
authors.lastname: Smith
authors.forename: J
authors.initials: J
authors.lastname: Best
authors.forename: A
authors.initials: A
authors.lastname: Blane
authors.forename: K P
authors.initials: KP
authors.lastname: Ebmeier
authors.forename: M F
authors.initials: MF
authors.lastname: Glabus
authors.forename: R E
authors.initials: RE
authors.lastname: O'Carroll
mesh_terms: D000368:Aged; D000679:Amygdala / Q000473:pathology; D001284:Atrophy; D002545:Brain Ischemia / Q000473:pathology*; D004632:Emergency Medical Services; D005260:Female; D006323:Heart Arrest / Q000150:complications*; D006624:Hippocampus / Q000098:blood supply / Q000473:pathology*; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008569:Memory Disorders / Q000209:etiology* / Q000473:pathology*; D011939:Mental Recall; D008875:Middle Aged; D009483:Neuropsychological Tests