title: Persistent trigeminal artery and its variants on MR angiography.
abstract: BACKGROUND
  A persistent trigeminal artery (PTA) is the most common carotid-vertebrobasilar anastomosis. A cerebellar artery that arises from the precavernous segment of the internal carotid artery (ICA) without connecting to the basilar artery is regarded as a PTA variant. Our study aimed to determine the incidence of PTA and its variants and classify them based on magnetic resonance (MR) angiography.
  
  
  METHODS
  We retrospectively reviewed cranial images of 3,626 patients who underwent MR angiography in our institution from April 1, 2007 through December 31, 2009. We ultimately reviewed and analyzed images of 3,491 patients (2,066 men, 1,425 women) after excluding 135 with unilateral or bilateral ICA occlusion or suboptimal image quality.
  
  
  RESULTS
  We found 12 cases of PTA (7 men, 5 women; right 4, left 8; incidence; 0.34%) and 6 of PTA variants (3 men, 3 women; right 3, left 3; incidence; 0.17%). 11 of the 12 PTAs were lateral type; 1 was medial. In two of the lateral-type cases, the superior cerebellar artery (SCA) arose from the PTA. Among the six variants, the anterior inferior cerebellar artery (AICA) arose in five and the posterior inferior cerebellar artery (PICA), in one.
  
  
  CONCLUSIONS
  On MR angiography, the incidence of PTA was 0.34% and of PTA variants, 0.17%. Left PTA was twice as frequent as right PTA, but with no statistical significance. Medial-type PTA was extremely rare. AICA arose in most PTA variants. Rarely, a lateral-type PTA gave rise to the cerebellar artery.
authors: Department of Diagnostic Radiology, Saitama Medical University International Medical Center, 1397-1 Yamane, Hidaka, Saitama, 350-1298, Japan. auchino@saitama-med.ac.jp
authors: Akira
authors: A
authors: Uchino
authors: Naoko
authors: N
authors: Saito
authors: Yoshitaka
authors: Y
authors: Okada
authors: Eito
authors: E
authors: Kozawa
authors: Waka
authors: W
authors: Mizukoshi
authors: Kaiji
authors: K
authors: Inoue
authors: Masahiro
authors: M
authors: Takahashi
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002339:Carotid Arteries / Q000033:anatomy & histology* / Q000000981:diagnostic imaging; D005260:Female; D006801:Humans; D018810:Magnetic Resonance Angiography; D008297:Male; D008875:Middle Aged; D011859:Radiography; D012189:Retrospective Studies; D055815:Young Adult