Outline Anatomy of Intracranial Vessels and Vascular Territories ECNR 2018 Intracranial ICA and its branches Circle of Willis and variants Cortical territories (ACA, MCA, PCA) Perforating vessels arising form Circle of Willis Vetebro-basilar system UCL Institute of Neurology Queen Square, London Bouthillier classification of ICA Bouthillier classification of ICA 1. cervical segment 2. petrous (horizontal) segment 1. cervical segment 3. lacerum segment 2. petrous (horizontal) segment 4. cavernous segment 3. lacerum segment 4. cavernous segment 5. clinoid segment 6. ophthalmic (supraclinoid) segment 7. communicating (terminal) segment 5. clinoid segment 6. ophthalmic (supraclinoid) segment 7. communicating (terminal) segment 1 cervical 2 ascending intra-petrous 3 horizontal intra-petrous 4 ascending foramen lacerum 5 horizonantal intracavernous 6 clinoid 7 termination Proximal Branches ICA MHT ILT PCOM Infundibulum and PCOM Aneurysm Enlarged Meningohypohyseal Trunk Meningioma MHT branches: 1. marginal tentorial a. (Bernasconi-Casanari artery) 2. clival branches 3. inferior hypophyseal a. Enlarged Meningohypohyseal Trunk: AVM Anterior Choroidal Artery DWI ADC FA 3D TOF MRA MPR Circle of Willis Thomas Willis (1621-1675) It is not a circle but a nonagon! Cerebri Anatome cui Accessit Nervorum Descriptivo et Usus (1664) Common Variations of Circle of Willis Common Variations of Circle of Willis 20% Foetal PCA Variations of Circle of Willis 10% Bilateral Foetal PCA Absent left A1 , Foetal origin PCA Complete circle 42% of general Western population (1) 90% of Japanese population (2) 27% in Chinese population (3) (1) Krabbe Hartkamp 1998; (2) Tanaka 2006; (3) Qi Li 2011 Basilar Artery In Presence of R Foetal PCA Cortical Territories 10% Absent A1 Cortical Territories Anterior Cerebral Artery Anterior Cerebral Artery Anterior Cerebral Artery A3 A3 A2 A2 A1 A1 horizontal segment Lt ACA Infarct A2 vertical segment A3 callosal segment Bilateral ACA Infarct Middle Cerebral Artery MCA Variations M4 M3 M2 M1 M1 Horizontal segment M2 Insular segment M3 Opercular segment M4 Cortical segment MCA Variants Fenestration of M1segment Left MCA Infarct Duplication of MCA Left MCA Infarct Posterior Cerebral Artery P4 P3 P2 P1 P1 pre-communicating segment P3 Quadrigeminal segment P2 brainstem segment P4 Cortical segment PCA Infarct Posterior Cerebral Artery Infarct T2 FSE DWI PCA- Splenium of Corpus Callosum Borderzone Territories Mangla Radiographics 2011 ACA/ MCA Borderzone 15 volunteers Hendrikse et al Radiology 2007 Right Borderzone Infarcts Variations in Perfusion Territories Van der Zwan & Billen, Stroke, 1991;22:1078-1084 Van der Zwan et al., J Neurosurg, 1992;77:927-940 Territorial Arterial Spin Labeling Normal Population: Non-variant Type COW 68 subjects 100% 0% Hendrikse et al. Stroke 35 (2004) Van Laar et al. Neuroimage 29:136 Normal Population Missing A1 segment (right) 144 (2006) Normal Population Unilateral foetal type PCA (right) 8 subjects 100% 100% Left ICA Left ICA Right ICA Right ICA VBA Van Laar et al. Neuroimage 29:136 0% 144 (2006) 19 subjects VBA Van Laar et al. Neuroimage 29:136 0% 144 (2006) Perforating Arteries of Circle of Willis Textbook Perfusion Territories of the BG Medial Perforators (incl Heubner) Lateral Perforators Thalamoperforators Thalamogeniculate Images from The Radiology Assistant , http://www.radiologyassistant.nl/en/484b8328c b6b2 Lenticular and Perforating Arteries Lenticulostriate Arteries Images from The Radiology Assistant , http://www.radiologyassistant.nl/en/484b8328c b6b2 Lenticulostriate Territory Infarct Recurrent Artery of Heubner Otto Heubner 1848-1926 Artery of Percheron Aneurysm and Infarct Thalamoperforators AOP- artery of Percheron G. Percheron. 1973 Hopital de la , Paris. Lazzaro AJNR 2010 31: 1283-1289 Perfusion Territories of the BG Vertebrobasilar Sytem Non-variant Circle of Willis Perforators SCA Hypoplastic L A1 Foetal R PCA AICA PICA Ant Spin A. Hendrikse et al. Radiology 254(3):867-875 (2010) Vertebrobasilar Sytem Lateral View Haemodynamic Balance between AICA and PICA AICA/PICA Haemodynamic Balance PICA dominant AICA dominant Duplication of R SCA R AICA dominant L PICA dominant L PICA Infarct Brainstem Perforators : Medulla Lateral = PICA Medial = Vertebral Brainstem Perforators Territories