title: Seventy aneurysms of the posterior inferior cerebellar artery: anatomical features and value of computed tomography angiography in microneurosurgery.
abstract: OBJECTIVE
  Aneurysms at the junction of the vertebral artery (VA) and posterior inferior cerebellar artery (PICA) are relatively rare. Their treatment is challenged by the diverse anatomy of the VA and PICA, close involvement of the PICA in the aneurysm neck, and scant space deep in the posterior fossa next to the cranial nerves, brain stem, and obstructing structures of the skull base. Computed tomography angiography (CTA) visualizes bony structures in addition to the vasculature, and being noninvasive and easily available, it can serve for planning microsurgical treatment. We analyzed the anatomy of PICA aneurysms imaged by CTA to promote planning the treatment.
  
  
  METHODS
  We examined the CTA images of 70 consecutive patients with a saccular PICA aneurysm who were all treated in the Department of Neurosurgery, Helsinki, Finland, 2001 to 2011.
  
  
  RESULTS
  Each of the 70 patients had 1 aneurysm at the VA-PICA junction. The proportion of small aneurysms (<7 mm) was high, 67%. The dome-to-neck ratio was <1.2 in 24 (34%) of the aneurysms. In the coronal view, 58 (83%) aneurysms projected cranially, and only 2 (3%) caudally. The aneurysms were located from 1 mm below the foramen magnum to 31 mm above it, most arising at the level of the jugular tubercle. The median distance to the aneurysm from the midline was 6 mm, ranging from 7.5 mm contralateral to the origin of the parent artery to 14 mm ipsilateral. Compared with the right VA, the left VA was larger, it harbored the most aneurysms, and its aneurysms were more often ruptured.
  
  
  CONCLUSIONS
  Relation of PICA aneurysms to skull base structures is highly variable; the aneurysms can also be extracranial, or lie on the site of the skull contralateral to the origin of the parent artery. These anatomical variations demand meticulous study of the angiography in each individual case, especially before surgical treatment of the aneurysm.
authors.affiliation: Department of Neurosurgery, Helsinki University Central Hospital, Helsinki, Finland. Electronic address: hanna.lehto@hus.fi.
authors.forename: Hanna
authors.initials: H
authors.lastname: Lehto
authors.affiliation: Department of Neurosurgery, Helsinki University Central Hospital, Helsinki, Finland.
authors.forename: Riku
authors.initials: R
authors.lastname: Kivisaari
authors.affiliation: Department of Neurosurgery, Helsinki University Central Hospital, Helsinki, Finland.
authors.forename: Mika
authors.initials: M
authors.lastname: Niemelä
authors.affiliation: Department of Neurosurgery, Helsinki University Central Hospital, Helsinki, Finland.
authors.forename: Reza
authors.initials: R
authors.lastname: Dashti
authors.affiliation: Department of Neurosurgery, Helsinki University Central Hospital, Helsinki, Finland.
authors.forename: Ahmed
authors.initials: A
authors.lastname: Elsharkawy
authors.affiliation: Department of Neurosurgery, Helsinki University Central Hospital, Helsinki, Finland.
authors.forename: Ali
authors.initials: A
authors.lastname: Harati
authors.affiliation: Department of Neurosurgery, Helsinki University Central Hospital, Helsinki, Finland.
authors.forename: Jarno
authors.initials: J
authors.lastname: Satopää
authors.affiliation: Department of Neurosurgery, Helsinki University Central Hospital, Helsinki, Finland.
authors.forename: Päivi
authors.initials: P
authors.lastname: Koroknay-Pál
authors.affiliation: Department of Neurosurgery, Helsinki University Central Hospital, Helsinki, Finland.
authors.forename: Aki
authors.initials: A
authors.lastname: Laakso
authors.affiliation: Department of Neurosurgery, Helsinki University Central Hospital, Helsinki, Finland.
authors.forename: Juha
authors.initials: J
authors.lastname: Hernesniemi
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002526:Cerebellar Diseases / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery*; D002533:Cerebral Angiography; D002548:Cerebral Revascularization / Q000379:methods*; D057510:Endovascular Procedures / Q000379:methods; D005260:Female; D006801:Humans; D002532:Intracranial Aneurysm / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D019635:Neurosurgical Procedures / Q000379:methods*; D012189:Retrospective Studies; D009626:Terminology as Topic; D014057:Tomography, X-Ray Computed
keywords: Anatomy; Cerebral aneurysm; Computed tomography angiography; Posterior inferior cerebellar artery; Vertebral artery