title: Value of delayed MRI in angiogram-negative subarachnoid haemorrhage.
abstract: OBJECTIVE
  To assess the efficacy of delayed magnetic resonance imaging (MRI) in identifying a structural cause for angiogram-negative subarachnoid haemorrhage.
  
  
  METHODS
  All patients presenting with spontaneous subarachnoid haemorrhage who had negative computed tomography (CT) angiography and catheter angiography between 2006 and 2012 were reviewed.
  
  
  RESULTS
  During the 6 year period, 1023 angiograms were performed for a new presentation of subarachnoid haemorrhage. Of these, 242 (23.7%) did not show a cause for the haemorrhage. A second catheter angiogram was performed in 48 patients, and aneurysms were identified in two patients. Of the remaining 240 patients, 131 underwent a subsequent MRI brain. One hundred and five (80.2%) MRI examinations were performed 4 or more weeks after angiography. In two patients, cavernomas were identified as the likely bleeding source. In both patients, the pattern of subarachnoid haemorrhage surrounding a small intraparenchymal haemorrhage on the initial CT suggested the diagnosis. Thirty-nine patients underwent MRI of the cervical spine, none of which identified a cause for the haemorrhage. None of the patients re-presented to our centre during the 6 year study period.
  
  
  CONCLUSIONS
  Delayed MRI following angiogram-negative subarachnoid haemorrhage has a low (1.5%) yield and is not routinely necessary. MRI may be useful to characterize the diagnosis in patients with clinical or radiological features of an underlying abnormality such as a cavernoma.
authors.affiliation: Department of Neurosurgery, John Radcliffe Hospital, Oxford, UK. Electronic address: julie.woodfield@nhs.net.
authors.forename: J
authors.initials: J
authors.lastname: Woodfield
authors.affiliation: Department of Neuroradiology, John Radcliffe Hospital, Oxford, UK.
authors.forename: N
authors.initials: N
authors.lastname: Rane
authors.affiliation: Department of Neurosurgery, John Radcliffe Hospital, Oxford, UK.
authors.forename: S
authors.initials: S
authors.lastname: Cudlip
authors.affiliation: Department of Neuroradiology, John Radcliffe Hospital, Oxford, UK.
authors.forename: J V
authors.initials: JV
authors.lastname: Byrne
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015901:Angiography, Digital Subtraction; D001921:Brain / Q000473:pathology*; D002533:Cerebral Angiography; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D013131:Spine / Q000473:pathology*; D013345:Subarachnoid Hemorrhage / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000473:pathology / Q000503:physiopathology; D013997:Time Factors; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome; D006113:United Kingdom / Q000453:epidemiology