II. Anatomy: Posterior Circulation

  1. Bilateral Vertebral Arteries
    1. Bilateral subclavian arteries (arising from aortic arch) branch into the bilateral Vertebral arteries
    2. Vertebral arteries ascend each side of the Cervical Vertebrae (via their bilateral transverse foramina)
    3. Vertebral arteries provide branch to Anterior Spinal Artery, and to the posterior inferior Cerebellum artery (PICA)
    4. Vertebral arteries combine to form Basilar Artery at level of Medulla
  2. Basilar Artery
    1. Basilar Artery branches to Cerebellum (AICA, SCA) and Brainstem
    2. Basilar Artery divides to form bilateral posterior cerebral arteries
  3. Posterior Cerebral Arteries
    1. Each Posterior Cerebral Artery connects to the ipsilateral Anterior Circulation via the posterior communicating arteries
  4. Function
    1. Posterior Circulaion supplies Occipital Lobe, inferior Temporal Lobe, Brain Stem and Cerebellum

III. Pathophysiology: Cerebrovascular Accident

  1. Vertebrobasilar obstruction may result in Vision Loss, Vertigo or Brain Stem effects
    1. See Vertebrobasilar CVA
    2. See Posterior Cerebral Artery CVA
    3. See Posterior Inferior Cerebellar Artery CVA
  2. Basilar Artery obstruction near the Vertebral Artery junction (before giving rise to the posterior cerebral arteries)
    1. Results in complete cortical blindness (bilateral Occipital Lobe infarcts)
  3. Basilar Artery obstruction in pons (Locked-In Syndrome)
    1. Complete motor paralysis except preserved diaphragmatic breathing and vertical eye movements
    2. Neurologic function otherwise intact (Awake, alert and lucid with intact cognitive function, and intact Sensation)
  4. Cerebellar artery obstruction
    1. Affects Cerebellum and Brain Stem
  5. Vertebral Artery obstruction
    1. May lack physical findings due to collateral circulation
  6. Posterior Cerebral Artery Aneurysm (1% of Cerebral Aneurysms)
    1. Cranial Nerve 3 (Oculomotor Nerve) passes between Superior Cerebellar Artery and Posterior Cerebral Artery
    2. Compression of Cranial Nerve 3 may result in Mydriasis and Cranial Nerve 3 Extraocular Movement deficit

IV. References

  1. Gilman (1989) Manter and Gatz Essentials of Neuroanatomy and Neurophysiology, Davis, p. 216-21
  2. Goldberg (2014) Clinical Neuroanatomy, Medmaster, p. 6-15
  3. Netter (1997) Atlas Human Anatomy, ICON Learning, p. 130-9

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