title: Perimesencephalic hemorrhage and CT angiography: A decision analysis.
abstract: OBJECTIVE
  The method of choice for detecting or excluding a vertebrobasilar aneurysm still is a matter of debate in patients with a characteristically perimesencephalic pattern of subarachnoid hemorrhage (SAH) on CT. We used decision analysis to compare possible diagnostic strategies in these patients.
  
  
  METHODS
  A decision analytic model was developed to evaluate the effect of 4 different diagnostic strategies following a perimesencephalic pattern of SAH on CT: 1, no further investigation; 2, digital subtraction angiography (DSA) by catheter; 3, CT angiography as initial modality, not followed by DSA if negative; and 4, CT angiography as initial modality, followed by DSA. We used a 4% prevalence of a vertebrobasilar aneurysm given a perimesencephalic pattern of hemorrhage, a 97% sensitivity and specificity of CT angiography, and a 99.5% sensitivity and 100% specificity of DSA. In a prospectively collected series, the complication rate from DSA in patients with a perimesencephalic pattern of hemorrhage was 2.6%. We calculated the expected utility of each of the 4 diagnostic options and used sensitivity analyses to examine the influence of the plausible ranges of the various estimates used.
  
  
  RESULTS
  The expected utilities were 99.09 for CT angiography only, 98.96 for no further investigation, 98.22 for DSA, and 96.34 for CT angiography plus DSA. The results of the sensitivity analysis indicate that over a wide range of assumptions, CT angiography only is the most beneficial option. Only when the complication rate of catheter angiography is <0.2% is DSA the preferred strategy.
  
  
  CONCLUSIONS
  Our decision analysis shows that in patients with a perimesencephalic pattern of hemorrhage on CT, CT angiography only is the best diagnostic strategy. DSA can be omitted in patients with a perimesencephalic pattern of hemorrhage and a negative CT angiogram.
authors: Department of Neurology, University Medical Center Utrecht, (Netherlands). ij.m.ruigrok@neuro.azu.nl
authors: Y M
authors: YM
authors: Ruigrok
authors: G J
authors: GJ
authors: Rinkel
authors: E
authors: E
authors: Buskens
authors: B K
authors: BK
authors: Velthuis
authors: J
authors: J
authors: van Gijn
mesh_terms: D015901:Angiography, Digital Subtraction / Q000379:methods / Q000706:statistics & numerical data*; D002533:Cerebral Angiography / Q000379:methods / Q000706:statistics & numerical data*; D002543:Cerebral Hemorrhage / Q000000981:diagnostic imaging*; D003661:Decision Support Techniques; D003663:Decision Trees; D006801:Humans; D002532:Intracranial Aneurysm / Q000000981:diagnostic imaging / Q000453:epidemiology; D008636:Mesencephalon / Q000098:blood supply* / Q000000981:diagnostic imaging; D015995:Prevalence; D011379:Prognosis; D012422:Rupture, Spontaneous / Q000000981:diagnostic imaging / Q000453:epidemiology; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000379:methods / Q000706:statistics & numerical data*; D014711:Vertebral Artery / Q000000981:diagnostic imaging