title: Regional cerebral blood flow levels as measured by xenon-CT in vascular territorial low-density areas after subarachnoid hemorrhage are not always ischemic.
abstract: BACKGROUND
  The aim of this study was to assess regional cerebral blood flow (rCBV) in areas of CT hypoattenuation appearing in the postoperative period in patients treated for aneurysmal subarachnoid hemorrhage (SAH) using xenon-enhanced CT scanning (Xe-CT).
  
  
  METHODS
  We analyzed 15 patients (5 male and 10 female; mean age 49.7+/-12.1 years) with SAH on CT performed on admission to hospital and who showed a low-density area within a well-defined vascular territory on CT scans after clipping or coiling of a saccular aneurysm. All zones of hypoattenuation were larger than 1 cm(2) and showed signs of a mass effect suggesting a subacute phase of evolution. Two aneurysms were detected in two patients. Aneurysms were located in the middle cerebral artery (n=7), in the anterior communicating artery (n=6), in the internal carotid artery (n=3), and in the posterior communicating artery (n=1). Treatments were surgical (n=8), endovascular (n=2) or both (n=1). A total of 36 Xe-CT studies were performed and rCBF values were measured in two different regions of interest (ROI): the low-density area, and an area of normal-appearing brain tissue located symmetrically in the contralateral hemisphere.
  
  
  RESULTS
  rCBF levels were significantly lower in the low-density area than in the contralateral normal-appearing area (P<0.01). In the low-density areas, irreversible ischemia (CBF <10 ml/100 g per minute) was present in 11/36 lesions (30.6%), ischemic penumbra (CBF 10-20 ml/100 g per minute) and oligemia (CBF 20-34 ml/100 g per minute) in 8/36 lesions (22.2%), relative hyperemia (CBF 34-55 ml/100 g per minute) in 7/36 lesions (19.4%), and absolute hyperemia (CBF >55 ml/100 g per minute) in 2/36 lesions (5.6%).
  
  
  CONCLUSIONS
  Our study confirmed that rCBF is reduced in new low-density lesions related to specific vascular territories. However, only about one-third of the lesions showed rCBF levels consistent with irreversible ischemia and in a relatively high proportion of lesions, rCBF levels indicated penumbral, oligemic and hyperemic areas.
authors.affiliation: Neuroradiology Unit, Department of Neurosciences, Arcispedale S Anna, Corso della Giovecca 203, 44100, Ferrara, Italy. henryfai@tin.it
authors.forename: E
authors.initials: E
authors.lastname: Fainardi
authors.forename: M F
authors.initials: MF
authors.lastname: Tagliaferri
authors.forename: C
authors.initials: C
authors.lastname: Compagnone
authors.forename: A
authors.initials: A
authors.lastname: Tanfani
authors.forename: F
authors.initials: F
authors.lastname: Cocciolo
authors.forename: R
authors.initials: R
authors.lastname: Battaglia
authors.forename: M
authors.initials: M
authors.lastname: Frattarelli
authors.forename: R
authors.initials: R
authors.lastname: Pascarella
authors.forename: L
authors.initials: L
authors.lastname: Targa
authors.forename: A
authors.initials: A
authors.lastname: Chieregato
mesh_terms: D002560:Cerebrovascular Circulation; D003287:Contrast Media; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D013345:Subarachnoid Hemorrhage / Q000000981:diagnostic imaging / Q000503:physiopathology*; D014057:Tomography, X-Ray Computed; D014978:Xenon
chemical_list: D003287:Contrast Media; D014978:Xenon