II. Anatomy: Posterior Circulation
- Bilateral Vertebral Arteries
- Bilateral subclavian arteries (arising from aortic arch) branch into the bilateral Vertebral arteries
- Vertebral arteries ascend each side of the Cervical Vertebrae (via their bilateral transverse foramina)
- Vertebral arteries provide branch to Anterior Spinal Artery, and to the posterior inferior Cerebellum artery (PICA)
- Vertebral arteries combine to form Basilar Artery at level of Medulla
- Basilar Artery
- Basilar Artery branches to Cerebellum (AICA, SCA) and Brainstem
- Basilar Artery divides to form bilateral posterior cerebral arteries
- Posterior Cerebral Arteries
- Each Posterior Cerebral Artery connects to the ipsilateral Anterior Circulation via the posterior communicating arteries
- Function
- Posterior Circulaion supplies Occipital Lobe, inferior Temporal Lobe, Brain Stem and Cerebellum
III. Pathophysiology: Cerebrovascular Accident
- Vertebrobasilar obstruction may result in Vision Loss, Vertigo or Brain Stem effects
- See Vertebrobasilar CVA
- See Posterior Cerebral Artery CVA
- See Posterior Inferior Cerebellar Artery CVA
- Basilar Artery obstruction near the Vertebral Artery junction (before giving rise to the posterior cerebral arteries)
- Results in complete cortical blindness (bilateral Occipital Lobe infarcts)
- Basilar Artery obstruction in pons (Locked-In Syndrome)
- Complete motor paralysis except preserved diaphragmatic breathing and vertical eye movements
- Neurologic function otherwise intact (Awake, alert and lucid with intact cognitive function, and intact Sensation)
- Cerebellar artery obstruction
- Affects Cerebellum and Brain Stem
- Vertebral Artery obstruction
- May lack physical findings due to collateral circulation
- Posterior Cerebral Artery Aneurysm (1% of Cerebral Aneurysms)
- Cranial Nerve 3 (Oculomotor Nerve) passes between Superior Cerebellar Artery and Posterior Cerebral Artery
- Compression of Cranial Nerve 3 may result in Mydriasis and Cranial Nerve 3 Extraocular Movement deficit
IV. References
- Gilman (1989) Manter and Gatz Essentials of Neuroanatomy and Neurophysiology, Davis, p. 216-21
- Goldberg (2014) Clinical Neuroanatomy, Medmaster, p. 6-15
- Netter (1997) Atlas Human Anatomy, ICON Learning, p. 130-9