title: Subarachnoid hemorrhage in the subacute stage: elevated apparent diffusion coefficient in normal-appearing brain tissue after treatment.
abstract: OBJECTIVE
  To prospectively evaluate whether subarachnoid hemorrhage (SAH) is associated with a change in the apparent diffusion coefficient (ADC) in normal-appearing brain parenchyma.
  
  
  METHODS
  Institutional review board approval and informed consent were obtained for all patient and volunteer studies. One hundred patients (48 men, 52 women; mean age, 52 years +/- 12 [standard deviation]) with aneurysmal SAH underwent conventional and diffusion-weighted magnetic resonance (MR) imaging at a mean of 9 days +/- 3 after SAH to evaluate possible lesions caused by SAH, treatment of SAH, and vasospasm. Aneurysms were treated surgically (n = 70) or endovascularly (n = 30) before MR imaging. Diffusion-weighted MR imaging was performed at 1-year follow-up in 30 patients (10 men, 20 women; mean age, 51 years +/- 11). Thirty healthy age-matched volunteers (11 men, 19 women; mean age, 54 years +/- 16) underwent MR imaging with an identical protocol. ADC values were measured bilaterally in the gray and white matter (parietal, frontal, temporal, occipital lobes; cerebellum; caudate nucleus; lentiform nucleus; thalamus; and pons) that appeared normal on T2-weighted and diffusion-weighted MR images. Linear mixed model was used for comparison of ADC values of supratentorial gray matter and white matter; general linear regression analysis was used for comparison of ADC values of cerebellum and pons.
  
  
  RESULTS
  In patients with SAH, the ADC values in normal-appearing white matter, with a single exception in the frontal lobe (P = .091), were significantly higher than they were in healthy volunteers (P </= .011). The differences disappeared by 1 year, except in parietal white matter (P = .045). The ADC values of cortical gray matter did not significantly differ between patients and volunteers (P >/= .121).
  
  
  CONCLUSIONS
  SAH and its treatment may cause global mild vasogenic edema in white matter and deep gray matter that is undetectable on T2-weighted and diffusion-weighted MR images but is detectable by measuring the ADC value in the subacute stage of SAH.
authors.affiliation: Department of Clinical Radiology, Kuopio University Hospital, PO Box 1777, FIN-70211 Kuopio, Finland. yawu.liu@kuh.fi
authors.forename: Yawu
authors.initials: Y
authors.lastname: Liu
authors.forename: Ville
authors.initials: V
authors.lastname: Soppi
authors.forename: Timo
authors.initials: T
authors.lastname: Mustonen
authors.forename: Mervi
authors.initials: M
authors.lastname: Könönen
authors.forename: Timo
authors.initials: T
authors.lastname: Koivisto
authors.forename: Anna
authors.initials: A
authors.lastname: Koskela
authors.forename: Jaakko
authors.initials: J
authors.lastname: Rinne
authors.forename: Ritva L
authors.initials: RL
authors.lastname: Vanninen
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001921:Brain / Q000473:pathology*; D016022:Case-Control Studies; D002421:Caudate Nucleus / Q000473:pathology; D002531:Cerebellum / Q000473:pathology; D003342:Corpus Striatum / Q000473:pathology; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005260:Female; D005500:Follow-Up Studies; D005625:Frontal Lobe / Q000473:pathology; D006801:Humans; D002532:Intracranial Aneurysm / Q000601:surgery; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D009778:Occipital Lobe / Q000473:pathology; D010296:Parietal Lobe / Q000473:pathology; D011149:Pons / Q000473:pathology; D011446:Prospective Studies; D013345:Subarachnoid Hemorrhage / Q000175:diagnosis* / Q000628:therapy; D013702:Temporal Lobe / Q000473:pathology; D013788:Thalamus / Q000473:pathology; D020301:Vasospasm, Intracranial / Q000175:diagnosis