title: Clinical course of nontraumatic, nonaneurysmal subarachnoid hemorrhage: a single-institution experience.
abstract: OBJECTIVE
  Angiogram-negative subarachnoid hemorrhage (SAH) accounts for 15% of nontraumatic SAH and has been reported with low morbidity and mortality rates. We report on a large series of patients with angiogram-negative SAH who experienced an atypical nonbenign clinical course.
  
  
  METHODS
  Between December 2001 and November 2006, 95 patients with spontaneous nonaneurysmal SAH and negative initial angiographic evaluation were treated at the University of Florida. The authors retrospectively reviewed the patients' medical records and radiological images to determine associated morbidity and mortality.
  
  
  RESULTS
  Aneurysms were found in 6 of the 95 patients on follow-up imaging after an initial negative angiogram (6.3% false negative rate); these patients were excluded leaving 89 patients as the study group. Hydrocephalus necessitating temporary CSF diversion developed in 22 of these patients (25%); 12 (13%) ultimately required permanent CSF diversion. Clinically significant vasospasm developed in 4 patients (4%), and 2 (2%) had cerebral infarctions. Three patients (3%) died.
  
  
  CONCLUSIONS
  The authors' experience with a large series of angiogram-negative SAH patients who had an atypical nonbenign clinical course associated with hydrocephalus, vasospasm, stroke, and mortality differs significantly from previously published case series of angiogram-negative SAH.
authors.affiliation: Department of Neurosurgery, University of Florida, Gainesville, Florida 32610, USA. whiting@neurosurgery.ufl.edu
authors.forename: Jobyna
authors.initials: J
authors.lastname: Whiting
authors.forename: John
authors.initials: J
authors.lastname: Reavey-Cantwell
authors.forename: Gregory
authors.initials: G
authors.lastname: Velat
authors.forename: Gregory
authors.initials: G
authors.lastname: Fautheree
authors.forename: Christopher
authors.initials: C
authors.lastname: Firment
authors.forename: Stephen
authors.initials: S
authors.lastname: Lewis
authors.forename: Brian
authors.initials: B
authors.lastname: Hoh
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002533:Cerebral Angiography; D002544:Cerebral Infarction / Q000401:mortality*; D015897:Comorbidity; D003937:Diagnosis, Differential; D005260:Female; D005431:Florida; D006801:Humans; D006849:Hydrocephalus / Q000401:mortality* / Q000601:surgery; D002532:Intracranial Aneurysm / Q000000981:diagnostic imaging / Q000401:mortality; D008297:Male; D008875:Middle Aged; D009026:Mortality; D011237:Predictive Value of Tests; D011379:Prognosis; D012189:Retrospective Studies; D012307:Risk Factors; D012720:Severity of Illness Index; D013345:Subarachnoid Hemorrhage / Q000000981:diagnostic imaging* / Q000401:mortality* / Q000503:physiopathology; D020301:Vasospasm, Intracranial / Q000401:mortality*; D055815:Young Adult