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Original research
Evaluation of an anatomic definition of non-aneurysmal perimesencephalic subarachnhoid hemorrhage
  1. Adam N Wallace1,
  2. Ross Vyhmeister2,
  3. Jeffrey N Dines3,
  4. Arindam R Chatterjee1,
  5. Akash P Kansagra1,
  6. Ryan Viets4,
  7. Justin T Whisenant5,
  8. Christopher J Moran6,
  9. DeWitte T Cross III6,
  10. Colin P Derdeyn7
  1. 1Mallinckrodt Institute of Radiology, Washington University School of Medicine, St Louis, Missouri, USA
  2. 2Washington University School of Medicine, St Louis, Missouri, USA
  3. 3Department of Radiology, Beth Israel Deaconess Medical Center, Boston, Massachusetts, USA
  4. 4Sharp Grossmont Hospital, La Mesa, California, USA
  5. 5Texas Radiology Associates, Plano, Texas, USA
  6. 6Mallinckrodt Institute of Radiology and Department of Neurological Surgery, Washington University, St Louis, Missouri, USA
  7. 7Mallinckrodt Institute of Radiology, Departments of Neurological Surgery and Neurology, Washington University School of Medicine, St Louis, Missouri, USA
  1. Correspondence to Dr Adam N Wallace, Mallinckrodt Institute of Radiology, Washington University School of Medicine, 510 South Kingshighway Boulevard, St Louis, MO 63110, USA; wallacea{at}


Background and purpose Perimesencephalic subarachnoid hemorrhage (PSAH) is not consistently defined in the existing literature. The purpose of this study was to test the inter-observer variability and specificity for non-aneurysmal subarachnoid hemorrhage (SAH) of an anatomic definition of PSAH.

Methods Medical records of all patients who underwent catheter angiography for evaluation of non-traumatic SAH between July 2002 and April 2012 were reviewed. Patients with anterior circulation aneurysms were excluded. Three blinded reviewers assessed whether each admission CT scan met the following anatomic criteria for PSAH: (1) center of bleeding located immediately anterior and in contact with the brainstem in the prepontine, interpeduncular, or posterior suprasellar cistern; (2) blood limited to the prepontine, interpeduncular, suprasellar, crural, ambient, and/or quadrigeminal cisterns and/or cisterna magna; (3) no extension of blood into the Sylvian or interhemispheric fissures; (4) intraventricular blood limited to incomplete filling of the fourth ventricle and occipital horns of the lateral ventricles (ie, consistent with reflux); (5) no intraparenchymal blood.

Results 56 patients with non-aneurysmal SAH and 50 patients with posterior circulation or posterior communicating artery aneurysms were identified. Seventeen (16%) of the 106 admission CT scans met the anatomic criteria for PSAH. No aneurysm was identified in this subgroup. Inter-observer agreement was excellent with κ scores of 0.89–0.96 and disagreement in 2.8% (3/106) of cases.

Conclusions Our anatomic definition of PSAH correlated with a low risk of brain aneurysm and was applied with excellent inter-observer agreement.

  • Aneurysm
  • Angiography
  • Stroke
  • CT
  • Hemorrhage

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