Vascular Neuroanatomy



Figure 3-1
Arterial anatomy





  • Endothelium



    • Single layer of cells lining the inner wall of arteries forming an interface between blood and tissue


    • Modulates tone, growth, hemostasis, and inflammation


  • Tunica Intima



    • Endothelial cells, and lower concentration of smooth muscle cells


    • Frequently the site of arterial dissection origin


  • Tunica Media



    • Mostly comprised of smooth muscle cells


    • Medial hyperplasia is the most common type of Fibromuscular Dysplasia


  • Tunica Adventitia



    • Collagen, elastin, fibrinous tissue


    • Dysfunctional in scurvy


  • Tunica Media and Adventitia are much thinner in intracranial vessels than extracranial vessels; hence, intracranial dissections may have higher risk of SAH







    Anterior Circulation Anatomy






    • Refer to Fig. 3.2

      A330798_1_En_3_Fig2_HTML.gif


      Figure 3-2
      Cerebrovascular anatomy


    • Aorta



      • Main source of cerebral blood supply


      • Brachiocephalic (innominate) artery: most proximal branch of aortic arch



        • Bifurcates into right common carotid and right subclavian arteries


        • Right vertebral artery originates from right subclavian artery


      • Left common carotid artery: usually the second main vessel off aortic arch


      • Left subclavian artery gives off left vertebral artery


      • Subclavian arteries give off internal thoracic arteries, thyrocervical and costocervical trunks


      • Bovine aortic arch: normal variant with shared origin of brachiocephalic artery and left common carotid artery (CCA)


    • Common carotid artery (CCA)



      • Travels within carotid sheath with internal jugular vein, vagus nerve, and ansa cervicalis


      • Bifurcates into external carotid and internal carotid arteries between C3-C5 vertebral levels (most commonly C4)



        • Bifurcation can be as high as C1 or as low as T2


    • Internal carotid artery (ICA)



      • Commonly originates posterolaterally to external carotid artery (ECA)


      • Dilates at the origin to form ICA “bulb,” which is 1–2 cm in length, then tapers


      • C1 (Cervical) segment: ascends distally to penetrate the skull base through carotid canal in the petrous temporal bone



        • Branches: none


      • C2 (Petrous) segment: courses medially in the horizontal plane, then cephalad to enter the posterior cavernous sinus



        • Branches: caroticotympanic artery (middle, inner ear), vidian artery, periosteal branches


      • C3 (Lacerum) segment



        • No branches


      • C4 (Cavernous) segment: complex course, runs anteriorly then cephalad, then posterolaterally through the carotid cave to pierce the dura



        • Branches: meningohypophyseal trunk, inferolateral trunk (can provide collateral anastomotic flow from ECA in the setting of ICA stenosis)



          • Meningohypophyseal trunk branches into inferior hypophyseal artery (which perfuses the pituitary gland), arteries of Bernasconi and Cassinari, and dorsal meningeal artery (perfuses abducens nerve)


          • Cavernous sinus



            • Holds ICA as well as cranial nerves III, IV, V1, V2, and VI


            • Only CN VI lies within the sinus; the other cranial nerves are located in the lateral dural wall


            • Receives blood from ophthalmic veins; drains into petrosal sinuses


          • Exits cavernous sinus through a dural ring


      • C5 (Supraclinoid) segment: first subarachnoid portion



        • Branches: ophthalmic, superior hypophyseal, posterior communicating, anterior choroidal


        • Ophthalmic artery: first major intracranial ICA branch


        • Ophthalmic artery occlusion: monocular vision loss


        • Anterior choroidal artery:



          • Originates from posterior aspect of ICA distal to the posterior communicating artery (PCOM)


          • Supplies internal segment of globus pallidus, part of posterior limb of internal capsule, part of geniculocalcarine tract, choroid plexus


        • Ends at middle cerebral/anterior cerebral artery bifurcation, also known as the “carotid T”


        • “T occlusions” are associated with extensive morbidity and mortality


      • Absent ICA: Congenital absence from agenesis, aplasia, hypoplasia can occur in less than 0.1 %



        • Collateral flow will occur through ACOM and PCOM


      • Aberrant ICA: Involution of cervical portion of ICA leads to enlargement of inferior tympanic and caroticotympanic arteries for collateral flow (through middle ear)



        • This enlargement can be associated with tinnitus


      • Carotid dissections most commonly start distal to the origin and below the entry into the skull


    • External carotid artery (ECA)



      • Differentiate from ICA by presence of cervical branches


      • Superior thyroid artery: first branch, supplies larynx and upper thyroid gland


      • Ascending pharyngeal artery: supplies pharynx, dura, lower cranial nerves


      • Facial artery: supplies most of face, palate, lip/cheek



        • Terminates as angular artery around the orbit, which anastomoses with branches of ophthalmic artery from ICA


      • Other branches include lingual, occipital, posterior auricular, maxillary, and superficial temporal arteries


    • Circle of Willis (COW )

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    Oct 7, 2017 | Posted by in NEUROLOGY | Comments Off on Vascular Neuroanatomy

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