ACKNOWLEDGMENT The UpToDate editorial staff acknowledges David Brock, MD, CIP, who contributed to earlier versions of this topic review. Use of UpToDate is subject to the Terms of Use. https://www.uptodate.com/contents/perimesencephalic-nonaneurysmal-subarachnoid-hemorrhage/print 12/28 7/7/23, 11:33 AM Perimesencephalic nonaneurysmal subarachnoid hemorrhage - UpToDate REFERENCES 1. Schwartz TH, Solomon RA. Perimesencephalic nonaneurysmal subarachnoid hemorrhage: review of the literature. Neurosurgery 1996; 39:433. 2. Rinkel GJ, Wijdicks EF, Hasan D, et al. Outcome in patients with subarachnoid haemorrhage and negative angiography according to pattern of haemorrhage on computed tomography. Lancet 1991; 338:964. 3. van Gijn J, van Dongen KJ, Vermeulen M, Hijdra A. Perimesencephalic hemorrhage: a nonaneurysmal and benign form of subarachnoid hemorrhage. Neurology 1985; 35:493. 4. Canh o P, Ferro JM, Pinto AN, et al. 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Topic 1114 Version 29.0 https://www.uptodate.com/contents/perimesencephalic-nonaneurysmal-subarachnoid-hemorrhage/print 19/28 7/7/23, 11:33 AM Perimesencephalic nonaneurysmal subarachnoid hemorrhage - UpToDate GRAPHICS Hunt and Hess grading system for patients with subarachnoid hemorrhage Grade Neurologic status 1 Asymptomatic or mild headache and slight nuchal rigidity 2 Severe headache, stiff neck, no neurologic deficit except cranial nerve palsy 3 Drowsy or confused, mild focal neurologic deficit 4 Stuporous, moderate or severe hemiparesis 5 Coma, decerebrate posturing Based upon initial neurologic examination. Adapted from: Hunt W, Hess R. Surgical risk as related to time of intervention in the repair of intracranial aneurysms. J Neurosurg 1968; 28:14. Graphic 69179 Version 5.0 https://www.uptodate.com/contents/perimesencephalic-nonaneurysmal-subarachnoid-hemorrhage/print 20/28 7/7/23, 11:33 AM Perimesencephalic nonaneurysmal subarachnoid hemorrhage - UpToDate Perimesencephalic nonaneurysmal subarachnoid hemorrhage Head CT of three different patients demonstrating subarachnoid hemorrhage in the characteristic pattern of perimesencephalic hemorrhage with blood in the interpeduncular and ambient cisterns. CT: computed tomography. Images are courtesy of the Neuroradiology teaching le and the Neurosurgery Department at Thomas Je erson University Hospital. Graphic 76973 Version 5.0 https://www.uptodate.com/contents/perimesencephalic-nonaneurysmal-subarachnoid-hemorrhage/print 21/28 7/7/23, 11:33 AM Perimesencephalic nonaneurysmal subarachnoid hemorrhage - UpToDate Subarachnoid spaces and cisterns as seen in a median section of the brain The superior cistern (located dorsal to the midbrain) together with the subarachnoid space at the sides of the midbrain are referred to clinically as the cisterna ambiens. The superior cistern is important because it contains internal cerebral veins, which join caudally to form the great cerebral vein (of Galen). It also contains the posterior cerebral and superior cerebellar arteries. The choroid plexuses in the roof of the third and fourth ventricles are shown in red. Graphic 74410 Version 5.0 https://www.uptodate.com/contents/perimesencephalic-nonaneurysmal-subarachnoid-hemorrhage/print 22/28 7/7/23, 11:33 AM Perimesencephalic nonaneurysmal subarachnoid hemorrhage - UpToDate Radiologic examples of perimesencephalic aneurysmal subarachnoid hemorrhage Head CT (A-C) and CTA (D) of a 70-year-old man 21 hours after ictus demonstrating a perimesencephalic bleeding pattern with an aneurysm of the basilar artery. Head CT (E-G) and CTA (H) of a 52-year-old woman 18 hours after ictus showing a nonperimesencephalic bleeding pattern (arrow points at extension to the lateral part of the Sylvian fissure and dashed arrow points to intraventricular hemorrhage) with an aneurysm of the basilar artery. CT: computed tomography; CTA: computed tomography angiography. From: Mensing LA, Vergouwen MDI, Laban KG, et al. Perimesencephalic Hemorrhage: A Review of Epidemiology, Risk Factors, Presumed Cause, Clinical Course, and Outcome. Stroke 2018; 49:1363. DOI: 10.1161/STROKEAHA.117.019843. Copyright 2018 American Heart Association. Reproduced with permission from Wolters Kluwer Health. Unauthorized reproduction of this material is prohibited. Graphic 118109 Version 3.0 https://www.uptodate.com/contents/perimesencephalic-nonaneurysmal-subarachnoid-hemorrhage/print 23/28 7/7/23, 11:33 AM Perimesencephalic nonaneurysmal subarachnoid hemorrhage - UpToDate Diagnostic imaging evaluation to exclude secondary causes of subarachnoid hemorrhage Imaging evaluation is typically performed for patients with spontaneous SAH to identify or exclude a ruptured cerebral aneurysm. Evaluation for nonaneurysmal causes is also warranted for patients with isolated convexity SAH who present with bleeding restricted to the surface of the cerebral hemispheres and for other patients once ruptured aneurysm has been excluded. Further https://www.uptodate.com/contents/perimesencephalic-nonaneurysmal-subarachnoid-hemorrhage/print 24/28 7/7/23, 11:33 AM Perimesencephalic nonaneurysmal subarachnoid hemorrhage - UpToDate imaging and/or other testing may be indicated for patients with acute SAH to monitor for complications and those who deteriorate clinically. Refer to UpToDate topic for additional details. SAH: subarachnoid hemorrhage; CT: computed tomography; DSA: digital subtraction angiography; CTA: computed tomographic angiography; MRI: magnetic resonance imaging. Refer to UpToDate topics for additional information on management of causes of SAH. Perimesencephalic pattern of acute SAH on head CT performed within 72 hours of onset consists of blood centered anterior to and in contact with the prepontine, interpeduncular, and/or suprasellar cisterns. Extent of blood on head CT should be restricted to the suprasellar, interpeduncular, crural, ambient, quadrigeminal, prepontine, and/or cerebellomedullary cisterns. Additional diagnostic testing is generally performed for patients with atypical features suggestive of a spinal source to bleeding such as those with prominent radicular symptoms and cervicomedullary location of bleeding or if the sensitivity of initial testing is limited by the presence of acute blood or vasospasm. Refer to UpToDate topic for additional details. Graphic 140106 Version 1.0 https://www.uptodate.com/contents/perimesencephalic-nonaneurysmal-subarachnoid-hemorrhage/print 25/28 7/7/23, 11:33 AM Perimesencephalic nonaneurysmal subarachnoid hemorrhage - UpToDate Radiologic examples of perimesencephalic nonaneurysmal subarachnoid hemorrhage (A-D) CT and CTA of a 47-year-old woman nine hours after ictus demonstrating a PM-NASAH. (E-H) CT and CTA of a 62-year-old man seven hours after ictus demonstrating a PM-NASAH with blood in front of the medulla oblongata (arrow). https://www.uptodate.com/contents/perimesencephalic-nonaneurysmal-subarachnoid-hemorrhage/print 26/28 7/7/23, 11:33 AM Perimesencephalic nonaneurysmal subarachnoid hemorrhage - UpToDate (I-L) CT and CTA of a 49-year-old woman 14 hours after ictus to illustrate a PM-NASAH with sedimentation of blood in the lateral horns (dashed arrows). (M-P) CT of a 66-year-old man 16 hours after ictus showing a PM-NASAH with the perimesencephalic cisterns filled with blood and associated hydrocephalus (M and N). CT on day seven after ictus showing a spontaneous decrease of hydrocephalus (O). CTA at time of presentation did not show an aneurysm (P). (Q-T) sagittal CT of a 47-year-old man four hours after ictus showing a PM-NASAH with distribution of blood in front of the brain stem and in the ambient cisterns. CT: computed tomography; CTA: computed tomography angiography; PM-NASAH: perimesencephalic subarachnoid hemorrhage From: Mensing LA, Vergouwen MDI, Laban KG, et al. Perimesencephalic Hemorrhage: A Review of Epidemiology, Risk Factors, Presumed Cause, Clinical Course, and Outcome. Stroke 2018; 49:1363. DOI: 10.1161/STROKEAHA.117.019843. Copyright 2018 American Heart Association. Reproduced with permission from Wolters Kluwer Health. Unauthorized reproduction of this material is prohibited. Graphic 118108 Version 3.0 https://www.uptodate.com/contents/perimesencephalic-nonaneurysmal-subarachnoid-hemorrhage/print 27/28 7/7/23, 11:33 AM Perimesencephalic nonaneurysmal subarachnoid hemorrhage - UpToDate Contributor Disclosures Farhan Siddiq, MD No relevant financial relationship(s) with ineligible companies to disclose. Amir S Khan, MD No relevant financial relationship(s) with ineligible companies to disclose. Jos Biller, MD, FACP, FAAN, FAHA No relevant financial relationship(s) with ineligible companies to disclose. Alejandro A Rabinstein, MD Grant/Research/Clinical Trial Support: Chiesi [Small investigator-initiated project]. Consultant/Advisory Boards: AstraZeneca [Secondary stroke prevention]; Brainomix [AI for stroke diagnostics]; Novo Nordisk [Stroke risk]; Shionogi [Stroke neuroprotection]. Other Financial Interest: Boston Scientific [Adverse event adjudication committee member for stroke risk reduction device in patients with atrial fibrillation]. All of the relevant financial relationships listed have been mitigated. Richard P Goddeau, Jr, DO, FAHA No relevant financial relationship(s) with ineligible companies to disclose. Contributor disclosures are reviewed for conflicts of interest by the editorial group. When found, these are addressed by vetting through a multi-level review process, and through requirements for references to be provided to support the content. Appropriately referenced content is required of all authors and must conform to UpToDate standards of evidence. Conflict of interest policy https://www.uptodate.com/contents/perimesencephalic-nonaneurysmal-subarachnoid-hemorrhage/print 28/28