title: Diffuse patterns of nonaneurysmal subarachnoid hemorrhage originating from the Basal cisterns have predictable vasospasm rates similar to aneurysmal subarachnoid hemorrhage.
abstract: BACKGROUND
  Nonaneurysmal subarachnoid hemorrhage (SAH) has been historically associated with a benign clinical course. However, recent studies have suggested that nonaneurysmal SAH can present with different hemorrhage patterns that may be associated with differential rates of morbidity. Herein, we analyze a retrospective consecutive cohort of patients with nonaneurysmal SAH to determine outcomes. We also seek to evaluate a validated radiographic grading scale to determine its utility in predicting vasospasm in the setting of different hemorrhage patterns.
  
  
  METHODS
  After institutional review board approval, the records of 563 consecutive patients admitted with spontaneous SAH between January 2007 and 2014 were retrospectively reviewed. A total of 138 of these patients had no identifiable source of hemorrhage and were further divided into 2 groups depending on their pattern of hemorrhage: perimesencephalic or diffuse. Clinical characteristics and outcomes were assessed.
  
  
  RESULTS
  In nonaneurysmal SAH, 70 patients (50.7%) had a perimesencephalic pattern of hemorrhage, whereas 68 (49.3%) experienced diffuse SAH. Radiographic vasospasm developed in 6 patients (8.6%) with perimesencephalic SAH and in 14 patients (20.6%) with a diffuse SAH pattern. When comparing historical rates of vasospasm based on the Barrow Neurological Institute (BNI) scale and rates in the nonaneurysmal diffuse pattern in this series, there was no significant difference in distribution (chi-square; P = .149), compared with a difference seen with the perimesencephalic group (P < .00001).
  
  
  CONCLUSIONS
  Nonaneurysmal SAH is associated with the potential for vasospasm, with higher rates in the diffuse versus perimesencephalic SAH patterns. The BNI grading scale for aneurysmal SAH can be used to predict the risk of vasospasm in diffuse, nonaneurysmal SAH.
authors: Department of Neurosurgery, Massachusetts General Hospital and Harvard Medical School, Boston, MA. Electronic address: walcott.brian@mgh.harvard.edu.
authors: Brian P
authors: BP
authors: Walcott
authors: Department of Neurosurgery, Massachusetts General Hospital and Harvard Medical School, Boston, MA.
authors: Christopher J
authors: CJ
authors: Stapleton
authors: Department of Neurosurgery, Massachusetts General Hospital and Harvard Medical School, Boston, MA.
authors: Matthew J
authors: MJ
authors: Koch
authors: Division of Neurosurgery, Department of Surgery, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA; Brain Aneurysm Institute, Beth Israel Deaconess Medical Center, Boston, MA.
authors: Christopher S
authors: CS
authors: Ogilvy
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000783:Aneurysm / Q000150:complications* / Q000209:etiology; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D012720:Severity of Illness Index; D013345:Subarachnoid Hemorrhage / Q000175:diagnosis* / Q000209:etiology*; D015898:Tomography Scanners, X-Ray Computed; D017585:Ultrasonography, Doppler, Transcranial; D020301:Vasospasm, Intracranial / Q000150:complications*; D055815:Young Adult
keywords: Aneurysm; hydrocephalus; subarachnoid hemorrhage; vasospasm