Neurovascular Anatomy (2): Posterior Circulation Anatomy Natthapon Rattanathamsakul, MD. December 28th, 2017 Contents: Neurovascular Anatomy ➢ Arterial supply of the brain ▪ Anterior circulation ▪ Posterior circulation ➢ Arterial supply of the spinal cord ➢ Venous system of the brain Neurovascular Anatomy (2): Anatomy of the Posterior Circulation ➢ Vertebral artery ➢ Basilar artery ➢ Blood supply of diencephalon, brainstem and cerebellum Vertebral Artery • Arise from the 1st part of subclavian artery • Course posteromedially to reach the transverse foramen of C6 vertebra • Run along the foramina then lie on the posterior arch of atlas (C1) • Through the dura, join with each other at pontomedullary junction Flemming KD, Jones LK. Mayo Clinic neurology board review: Basic science and psychiatry for initial certification. 2015 Vertebral Artery • Divided into 4 parts • V1: Ostium to transverse foramen of C6 • V2: Travels cephalad from C6 to C1 • V3: Lies on the posterior arch of C1 (atlas) • V4: Pierces dura, merges together at pontomedullary junction Netter FH. Atlas of human anatomy, 6th ed. 2014 Angiographic Correlation Uflacker R. Atlas of vascular anatomy: an angiographic approach, 2007 Angiographic Correlation Uflacker R. Atlas of vascular anatomy: an angiographic approach, 2007 MRI Correlation Uflacker R. Atlas of vascular anatomy: an angiographic approach, 2007 MRI Correlation Uflacker R. Atlas of vascular anatomy: an angiographic approach, 2007 MRI Correlation Uflacker R. Atlas of vascular anatomy: an angiographic approach, 2007 MRI Correlation Uflacker R. Atlas of vascular anatomy: an angiographic approach, 2007 Vertebral Artery Netter FH. Atlas of human anatomy, 6th ed. 2014 Vertebral Artery Branches of vertebral artery • Muscular arteries • Segmental medullary arteries • Forming anterior & posterior spinal arteries • Meningeal arteries • Perforating branches to medulla • Anterior spinal artery • Posterior inferior cerebellar artery (PICA) Műller KI, et al. Tidsskr Nor Legeforen. 2013; 133: 1320-4 Variation of VA Hypoplastic left VA • Asymmetry due to • Vertebral arterial hypoplasia • Absence of vertebral artery • Termination into the PICA • Dominance: Left 45%, right 30%, co- dominant 25% • Variations • Complete/partial VA duplication VA fenestration • VA fenestration • Variable origin • Aortic arch origin of left VA (5%) • 2nd part of subclavian artery • External carotid artery • Variable orientation of ostium https://radiopaedia.org Abnormal course of left VA Partial ECA origin of duplication of VA left VA Aortic arch origin of left VA https://radiopaedia.org http://www.anatomyatlases.org/ Vertebral Artery Dissection http://www.alamy.com/stock-photo-rotational-injury-of-the-vertebral-artery-7710492.html Rotational Vertebral Artery Occlusion (Bow Hunter’s Syndrome) Neutral position Turn head to left Stroke 2013; 44: 1817-24 J Korean Neurosurg Soc 2013; 54: 243-5 http://www.fanpop.com/ Effects of Neck Position on Vertebral Artery Am J Neuroradiol. 2014; 35: 323-6 Subclavian Steal Syndrome • Presence of occlusion of proximal subclavian artery • Blood flowing down the ipsilateral VA to supply the arm • Usually asymptomatic, or syncope/vertigo • Atherosclerosis • Caucasian, women > men Intern J Surg Case Rep. 2015; 16: 177-80 Circulation. 2014; 129: 2320-3 Posterior Inferior Cerebellar Artery • 5 segments: • Anterior medullary • Lateral medullary (forming caudal loop) • Tonsillomedullary • Telovelotonsillar (choroid point) • Cortical branches Branches Small perforating medullary branches Tonsillohemispheric branch Inferior vermian branch **Occasionally, branch off the AICA in the common stem World Neurosurg. 2017; 106: 493-503 Angiographic Correlation Uflacker R. Atlas of vascular anatomy: an angiographic approach, 2007 Posterior Inferior Cerebellar Artery Supply • Posteroinferior cerebellar hemisphere (up to great horizontal fissure) • Inferior portion of vermis • Lower part of medulla (50%) • Inferior cerebellar peduncle http://missinglink.ucsf.edu/ https://accessmedicine.mhmedical.com Development of Nervous System Medial brainstem syndrome • Affect motor Lateral brainstem syndrome • Affect sensation http://www.ultratwistersgym.com/Resources/Nervous/Nervous.html Brainstem Syndromes Cranial nerve Long tract signs Other brainstem involvement features Medial Midbrain : CN 3,4 Corticospinal tract MLF Pons : CN 6 Corticobulbar tract Medial lemniscus (for Medulla : CN 12 lower brainstem) Lateral Midbrain : none Lateral spinothal tract Cerebellar tract Pons : CN 5,7,8 Spinal tract of N.V Medial lemniscus (for Medulla : CN 9,10,11 Descending autonomic tr. upper brainstem) Hearing pathway Medial : ‘4Ms’ Lateral : ‘4Ss’ plus Motor nuclei : 3,4,6,12 Spinothalamic tract contralat Motor pathway Sensory tract of N.V Ipsilat Medial lemniscus Fine, proprio Sympathetic tract Horner MLF INO Spinocerebellar tract Plus CN5,7,8,9,10,11, vestibular 8 9 7 6 5 4 1: Pyramidal tract 2: Inferior olivary nuc. Complex 3: Medial lemniscus 11 4: MLF 10 5: Inferior cerebellar peduncle (restiform body) 3 6: Hypoglossal nucleus (XII) 12 7: Inferior salivatory nuc. (IX) 8: Nucleus & tractus solitaries 13 9: Vestibular nuclei 2 10: Ambiguus nucleus 11: Nuc. of spinal tract of N.V Post-olivary : 12: Spinothalamic tract CN.IX, X, XI 13: Descending sympathetic tract 1 Pre-olivary : CN.XII PICA Syndrome (Wallenburg) Clinical features : ‘4S plus’ Spinal tract of N.V • Loss of pain/temperature sensation of ipsilateral Spinothalamic tract face & contralateral body (alternating hemianesthesia) Spinocerebellar • Ipsilateral cerebellar sign Sympathetic tract • Ipsilateral Horner syndrome Plus • CN.IX, X • Dysphonia, dysarthria, dysphagia, absence of gag reflex • CN.XI • Ipsilateral shoulder drooping, difficulty turning head contralaterally • Vestibular nucleus • Vertigo, N/V, head impulse test • Area postrema • Persistent vomiting/hiccup (rare) http://www.radiologyassistant.nl Variations of PICA A Normal B AICA & PICA in common stem C Anastomosis between AICA & PICA D VA terminates into PICA E Distal PICA give rise the tonsillar loop to supply contralateral tonsil F Interhemispheric anastomosis NeuroiImage. 2013; 83: 58-65 Anterior Spinal Artery (Dejerine syndrome) Clinical features : ‘3M’ Motor • Contralateral hemiparesis pathway • Hemiplegia cruciata • Flaccid quadriplegia Motor nuclei • Ipsilateral tongue of CN.XII deviation/fasciculation Medial • Contralateral loss of fine lemniscus touch/proprioception Others • Upbeat nystagmus https://accessmedicine.mhmedical.com J Pak Med Assoc. 2013; 63(3): 387-9 Arm Leg Contralateral hemiplegia Hemiplegia cruciata Paraplegia Quadriplegia Ipsilateral hemiplegia SA Orthop J. 2012; 11(4): 43-47 http://yuandanisaputra.blogspot.com/2013/07/brain-varcularisation-and-ventricular_1983.html Hemimedullary infarction (Babinski-Nageotte syndrome, medullary tegmental paralysis) • Combined medial & lateral medullary infarction • Reported in the case of vertebral artery dissection/stenosis Arch Neurol. 2005; 62(4): 676-7 Neurology. 2001; 56(11): 1604 Dorsal Medullary Syndrome • Occlusion of medial branch of PICA • Involvement of vestibular nuclei & restiform body (ICP) • N/V, vertigo, ataxia to the affected side • Ipsilateral gaze-evoked nystagmus https://en.wikipedia.org Neurol India. 2016; 64(1): 121-8 J Clin Mov Disord. 2015; 2: 14 Submedullary Syndrome (Opalski syndrome) • Involvement of lateral medulla below the level of motor decussation • Ipsilateral weakness with contralateral hemianesthesia (like upper C lesion) • No facial weakness!! • Presence of palatal/tongue palsy, Horner syndrome, gaze-evoked nystagmus https://en.wikipedia.org Neurol India. 2016; 64(Suppl S1): 113-4 J Clin Diag Research. 2014; 8(7): MD05-MD06 Neurovascular Anatomy (2): Anatomy of the Posterior Circulation ➢ Vertebral artery ➢ Basilar artery ➢ Blood supply of diencephalon, brainstem and cerebellum Basilar Artery • Run along the basilar groove on the ventral surface of pons • Terminated at the CN.III pontomesencephalic junction PCA SCA Branches of basilar artery • Paramedian: Pontine artery Pontine • Short circumferential branches Basilar a. Basilar CN.VI • Long circumferential branches: Laby • Anterior inferior cerebellar AICA (AICA) • Labyrinthine artery PICA • Superior cerebellar artery (SCA) • Terminal branches Vertebral a. • Posterior cerebral artery (PCA) Postr spinal a. Antr spinal a. Uflacker R. Atlas of vascular anatomy: an Angiographic Correlation angiographic approach, 2007 1: Vertebral artery 5: SCA 17: Anterior spinal a. 6: PCA 2: PICA 4: AICA 3: Basilar artery 8: Posterior temporal branch of PCA Variation of BA • BA fenestration & other variable fusion • Persistent carotid-basilar artery anastomoses BA fenestration Unfused upper Unfused lower basilar basilar http://msk-anatomy.blogspot.com/2012/08/variation-in-fusion-patterns-of-basilar.html http://radiopaedia.org Penetrating Branches of BA Pract Neurol 2016; 16: 484-7 https://www.memorangapp.com/flashcards/94861/Neuroscience+L3-4+Internal+Anatomy/ 5 10 4 9 1: Pyramidal tract 8 5a 2: Pontocerebellar fibers 6 3: Medial lemniscus 6a 11 4: MLF 12 5: Inferior cerebellar peduncle 5a: Middle cerebellar peduncle 3 7 13 Pontine tegmentum Pontine (brachium pontis) 6: Abducens nucleus (VI) 6a: Paramedian pontine reticular formation (PPRF) pontis 7: Facial motor nucleus (VII) 1 8: Superior salivatory nuc (VII) Basis 9: Nucleus & tractus solitarius Post-olivary : 10: Vestibular nuclei 2 CN.VII 11: Nuc. of spinal tract of N.V 12: Spinothalamic tract 13: Descending sympathetic tract Pre-olivary : CN.VI