title: The bihemispheric posterior interior cerebellar artery: anatomic variations and clinical relevance in 11 cases.
abstract: OBJECTIVE
  Although the anatomic course of the posterior interior cerebellar artery (PICA) is variable, it is thought to be very rare for the artery to cross midline, with an estimated incidence of 0.1%. Bihemispheric PICA crosses midline and typically serves both PICA territories.
  
  
  METHODS
  We present 11 cases of bihemispheric PICA discovered from retrospective angiogram review, the largest to date reported in the literature.
  
  
  RESULTS
  Five cases were the typical bihemispheric PICA pattern, three were bihemispheric with distal vertebral hypoplasia, two cases were the vermian type, and one was atypical, with the PICA feeding a contralateral cerebellar arteriovenous malformation (AVM). The branching point to the contralateral hemisphere always occurred distal to the ascending tonsillar loop and all true bihemispheric variants had contralateral PICA aplasia.
  
  
  CONCLUSIONS
  The true incidence of this variant may be much higher than previously thought (3.6% in the current series), and has relevance for cerebrovascular disease, including aneurysm, AVM, and ischemic stroke. Neuroradiologists, neurologists, and neurosurgeons should be aware of this potential variant.
authors.affiliation: Department of Neurosurgery, Neuropsychiatric Institute (MC799), University of Illinois Hospital and Health Sciences System, College of Medicine, Chicago, Illinois, USA.
authors.forename: Andrew P
authors.initials: AP
authors.lastname: Carlson
authors.forename: Ali
authors.initials: A
authors.lastname: Alaraj
authors.forename: Reza
authors.initials: R
authors.lastname: Dashti
authors.forename: Victor A
authors.initials: VA
authors.lastname: Aletich
mesh_terms: D002526:Cerebellar Diseases / Q000473:pathology* / Q000601:surgery*; D002531:Cerebellum / Q000033:anatomy & histology* / Q000098:blood supply* / Q000473:pathology; D002533:Cerebral Angiography; D002536:Cerebral Arteries / Q000033:anatomy & histology* / Q000473:pathology / Q000601:surgery*; D002560:Cerebrovascular Circulation / Q000502:physiology; D004621:Embolization, Therapeutic / Q000379:methods; D007839:Functional Laterality; D006801:Humans; D007091:Image Processing, Computer-Assisted; D015994:Incidence; D002538:Intracranial Arteriovenous Malformations / Q000453:epidemiology / Q000473:pathology