title: The Posterior Limb of the Internal Capsule as the Subcortical Transitional Zone of the Anterior and Posterior Circulations: Insights from Human 7T MRI.
abstract: In patients with cerebral infarction, identifying the distribution of infarction and the relevant artery is essential for ascertaining the underlying vascular pathophysiological mechanisms and preventing subsequent stroke. However, visualization of the basal perforating arteries (BPAs) has had limited success, and simultaneous viewing of background anatomical structures has only rarely been attempted in living human brains. Our study aimed at identifying the BPAs with 7T MRI and evaluating their distribution in the subcortical structures, thereby showing the clinical significance of the technique.
  
  
  
  Twenty healthy subjects and 1 patient with cerebral infarction involving the posterior limb of the internal capsule (ICpost) and thalamus underwent 3-dimensional fast spoiled gradient-echo sequence as time-of-flight magnetic resonance angiography (MRA) at 7T with a submillimeter resolution. The MRA was modified to detect inflow signals from BPAs, while preserving the background anatomical signals. BPA stems and branches in the subcortical structures and their origins were identified on images, using partial maximum intensity projection in 3 dimensions.
  
  
  
  A branch of the left posterior cerebral artery (PCA) in the patient ran through both the infarcted thalamus and ICpost and was clearly the relevant artery. In 40 intact hemispheres in healthy subjects, 571 stems and 1,421 branches of BPAs were detected in the subcortical structures. No significant differences in the numbers of stems and branches were observed between the intact hemispheres. The numbers deviated even less across subjects. The distribution analysis showed that the subcortical structures of the telencephalon, such as the caudate nucleus, anterior limb of the internal capsule, and lenticular nucleus, were predominantly supplied by BPAs from the anterior circulation. In contrast, the thalamus, belonging to the diencephalon, was mostly fed by BPAs from the posterior circulation. However, compared with other subcortical structures, the ICpost, which marks the anatomical boundary between the telencephalon and the diencephalon, was supplied by BPAs with significantly more diverse origins. These BPAs originated from the internal carotid artery (23.1%), middle cerebral artery (38.5%), PCA (17.3%), and the posterior communicating artery (21.1%).
  
  
  
  The modified MRI method allowed the detection of the relevant BPA within the infarcted area in the stroke survivor as well as the BPAs in the subcortical structures of living human brains. Based on in vivo BPA distribution analyses, the ICpost is the transitional zone of the anterior and posterior cerebral circulations.
authors.affiliation: Department of Neurosurgery and Center for Integrated Human Brain Science, Brain Research Institute, University of Niigata, Niigata, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Kurabe
authors.forename: Kouichirou
authors.initials: K
authors.lastname: Okamoto
authors.forename: Kiyotaka
authors.initials: K
authors.lastname: Suzuki
authors.forename: Hisothi
authors.initials: H
authors.lastname: Matsuzawa
authors.forename: Masaki
authors.initials: M
authors.lastname: Watanabe
authors.forename: Yuji
authors.initials: Y
authors.lastname: Suzuki
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Nakada
authors.forename: Yukihiko
authors.initials: Y
authors.lastname: Fujii
mesh_terms: D000328:Adult; D000369:Aged, 80 and over; D020771:Anterior Cerebral Artery / Q000000981:diagnostic imaging* / Q000503:physiopathology; D002343:Carotid Artery, Internal / Q000000981:diagnostic imaging / Q000503:physiopathology; D016022:Case-Control Studies; D002533:Cerebral Angiography / Q000379:methods*; D002560:Cerebrovascular Circulation; D005260:Female; D006801:Humans; D020243:Infarction, Anterior Cerebral Artery / Q000000981:diagnostic imaging* / Q000503:physiopathology; D020762:Infarction, Posterior Cerebral Artery / Q000000981:diagnostic imaging* / Q000503:physiopathology; D020772:Internal Capsule / Q000098:blood supply / Q000000981:diagnostic imaging*; D018810:Magnetic Resonance Angiography; D020768:Middle Cerebral Artery / Q000000981:diagnostic imaging / Q000503:physiopathology; D020769:Posterior Cerebral Artery / Q000000981:diagnostic imaging* / Q000503:physiopathology; D011237:Predictive Value of Tests; D013786:Thalamic Diseases / Q000000981:diagnostic imaging* / Q000503:physiopathology; D013788:Thalamus / Q000098:blood supply / Q000000981:diagnostic imaging*; D055815:Young Adult