title: Spontaneous subarachnoid hemorrhage and negative initial vascular imaging--should further investigation depend upon the pattern of hemorrhage on the presenting CT?
abstract: BACKGROUND
  Multiple investigations are usually performed in patients with spontaneous SAH who have negative initial angiography. This study aimed to evaluate the most appropriate use of additional imaging studies and how this may be influenced by the findings of the initial CT.
  
  
  METHODS
  A retrospective analysis was performed on a prospectively collected cohort of patients referred with spontaneous SAH and negative initial angiography. The patients were divided into four categories based upon the distribution of blood on the initial CT: perimesencephalic (pSAH), diffuse (dSAH), sulcal (sSAH) and CT negative (CSF positive for xanthochromia) (nCT-pLP). The number and nature of the subsequent imaging investigations were reviewed, and the results were correlated with the findings of the presenting CT.
  
  
  RESULTS
  One hundred fourteen patients were included in the study. Repeat imaging found five relevant abnormalities. Three cases of vasculitis were diagnosed on the first DSA following a negative CTA. A case of dissecting aneurysm was revealed on the third neurovascular study. A hemorrhagic spinal tumor presented with xanthochromia. No subsequent abnormality was found on the third DSA or MRI head. No case of pSAH had a subsequent positive finding if the initial CTA was negative.
  
  
  CONCLUSIONS
  Certain patterns of SAH are associated with a low yield of abnormalities on repeat imaging if the initial angiography is normal. The authors believe that the pattern of hemorrhage on the presenting CT should be used to guide the most appropriate use of further imaging modalities and present a diagnostic algorithm for this purpose.
authors.affiliation: Department of Neuroradiology, Royal Hallamshire Hospital, Glossop Road, Sheffield, S10 2JF, UK, leesien@tiscali.co.uk.
authors.forename: L
authors.initials: L
authors.lastname: Yap
authors.forename: R A
authors.initials: RA
authors.lastname: Dyde
authors.forename: T J
authors.initials: TJ
authors.lastname: Hodgson
authors.forename: U J
authors.initials: UJ
authors.lastname: Patel
authors.forename: S C
authors.initials: SC
authors.lastname: Coley
mesh_terms: D000328:Adult; D002533:Cerebral Angiography; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D013345:Subarachnoid Hemorrhage / Q000175:diagnosis*; D014057:Tomography, X-Ray Computed