J Korean Neurosurg Soc.  2015 Nov;58(5):467-470. 10.3340/jkns.2015.58.5.467.

In Situ Intersegmental Anastomosis within a Single Artery for Treatment of an Aneurysm at the Posterior Inferior Cerebellar Artery: Closing Omega Bypass

  • 1Department of Neurosurgery, College of Medicine, Kyung Hee University, Seoul, Korea. nscsk@hanmail.net


A 74-year-old patient was diagnosed with a subarachnoid hemorrhage suspected from a dissecting aneurysm located at the lateral medullary segment of the posterior inferior cerebellar artery (PICA). Because perforators to the medulla arose both proximal and distal to the dissecting segment, revascularization for distal flow was essential. However, several previously reported methods for anastomosis, such as an occipital artery-PICA bypass or resection with PICA end-to-end anastomosis could not be used. Ultimately, we performed an in situ side-to-side anastomosis of the proximal loop of the PICA with distal caudal loops within a single artery, as a "closing omega," followed by trapping of the dissected segment. The aneurysm was obliterated successfully, with intact patency of the revascularized PICA.


Aneurysm; Posterior inferior cerebellar artery; Cerebral revascularization

MeSH Terms

Aneurysm, Dissecting
Cerebral Revascularization
Subarachnoid Hemorrhage


  • Fig. 1 A : Computed tomography at admission showed a large subarachnoid hemorrhage and an intraventricular hemorrhage. B : Vertebral angiography revealed proximal narrowing with aneurysm dilatation ("string and pearl" sign) (arrow), suggesting a dissecting aneurysm at the lateral medullary segment of the left posterior inferior cerebellar artery. The artery ran in an unusual pattern, forming dual loops at the lateral medullary segment. C : Dissecting aneurysm and its parent arteries were illustrated by the senior surgeon (blinded for review). D : Occipital artery (arrowheads) is shown via common carotid artery angiography because selection of the external carotid artery failed due to its extreme tortuosity. Its distal segments, candidates for bypass graft, become abruptly narrow.

  • Fig. 2 A : Operation photograph showing trapping of the dissected segment and side-to-side anastomosis. The aneurysm (not shown) is hidden behind the rootlets (arrow) of low cranial nerve. Whitish discoloration of the proximal segment of the dissection is also shown. B : Illustration showing the "closing omega" anastomosis, canalling of the proximal and distal caudal loops of a single artery. C : Reconstruction of the three-dimensional angiography at the first postoperative day showing successful obliteration of the aneurysm and intact patency of distal flow. D : CT at the 14th postoperative day shows no evidence of cerebral infarction.


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