title: Acute perfusion changes after spontaneous SAH: a perfusion CT study.
abstract: BACKGROUND
  Perfusion computed tomography (CT) is a rapid technique that allows the measurement of acute disturbances in local and global cerebral blood flow in patients suffering stroke and spontaneous subarachnoid haemorrhage (SAH). The purpose of this study was to establish the relationship between different measures of brain perfusion made on dynamic-contrast CT reconstructions performed as soon as SAH has been diagnosed and the severity of the bleeding determined by the clinical grade, the extent of the bleeding and the outcome of the patients.
  
  
  METHODS
  After the diagnosis of SAH by conventional CT, a perfusion CT was performed before CT angiography. All imaging studies were performed on a six-slice spiral CT scanner. All images were analysed using perfusion software developed by Philips, which produces perfusion CT quantitative data based on temporal changes in signal intensity during the first pass of a bolus of an iodinated contrast agent. Measurements of mean transient time (MTT), time to peak (TTP), cerebral blood volume (CBV) and cerebral blood flow (CBF) in volumes of interest corresponding to territories perfused by the major cerebral arteries were performed. Different data regarding severity of the bleeding-such as level of consciousness, amount of bleeding in conventional CT-were collected. All poor-grade patients received a ventriculostomy catheter so that ICP recordings were obtained. Also, the occurrence of delayed cerebral ischaemia (DCI) was recorded. Outcome was assessed by the Glasgow Outcome Scale 6 months after the bleeding. For statistical analysis, non-parametric correlations between variables were performed.
  
  
  RESULTS
  Thirty-nine patients have been included in the study since January 2007. In SAH patients there are increasing perfusion abnormalities as the severity of the bleeding increases. The most affected perfusion parameters are TTP and MTT, as they significantly increase with the clinical severity of the bleeding and the total volume of bleeding (P < 0.01, Spearman's Rho). When average MTT time is increased over 5.9 s there is a 20-fold (95% CI = 2.1-182) risk of poor outcome. All patients presenting this MTT time suffered from DCI. This value has a positive predictive value of 100% for DCI and 90% for a poor outcome.
  
  
  CONCLUSIONS
  SAH causes cerebral blood flow abnormalities even in the acute phase of the illness, consisting mainly of an increase in circulation times (TTP and MTT), which are correlated with the severity of the bleeding.
authors.affiliation: Department of Neurosurgery, Hospital 12 de Octubre, Crta de Andalucia km 5.4, Madrid, Spain. algadoc@yahoo.com
authors.forename: Alfonso
authors.initials: A
authors.lastname: Lagares
authors.forename: Marta
authors.initials: M
authors.lastname: Cicuendez
authors.forename: Ana
authors.initials: A
authors.lastname: Ramos
authors.forename: Elena
authors.initials: E
authors.lastname: Salvador
authors.forename: Jose F
authors.initials: JF
authors.lastname: Alén
authors.forename: Ariel
authors.initials: A
authors.lastname: Kaen
authors.forename: Luis
authors.initials: L
authors.lastname: Jiménez-Roldán
authors.forename: J M
authors.initials: JM
authors.lastname: Millán
mesh_terms: D000208:Acute Disease; D002536:Cerebral Arteries / Q000000981:diagnostic imaging* / Q000503:physiopathology; D002560:Cerebrovascular Circulation / Q000502:physiology*; D003287:Contrast Media; D005260:Female; D023261:Glasgow Outcome Scale; D006801:Humans; D008297:Male; D008875:Middle Aged; D055420:Perfusion Imaging / Q000379:methods*; D011237:Predictive Value of Tests; D011379:Prognosis; D013345:Subarachnoid Hemorrhage / Q000000981:diagnostic imaging* / Q000503:physiopathology; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D003287:Contrast Media