Radiological vascular anatomy of brain

radiology arterial venous vascular anatomy of brain

1. NORMAL ARTERIAL AND VENOUS ANATOMY OF BRAIN AND ITS TERRITORIES D R. DEV LAKHERA

2. Imaging techniques Arterial anatomy of brain, variants and territories Anterior circulation Circle of Willis Posterior circulation Venous anatomy of brain

3. IMAGING TECHNIQUES Digital Subtraction Angiography (DSA). Computed Tomography Angiography (CTA). Magnetic Resonance Angiography (MRA).

4. DSA Endovascular interventional procedures. Follow-up DSA after aneurysm and AVM treatment. Negative CTA, in order to exclude a small fistula.

5. CT Angiography Anatomy and pathology Contrast enhanced CT angiography Adv over MR Angiography Quicker and easier to perform Can be used in MR contraindications

6. MR Angiography Contrast enhanced MR angiography- Non-contrast enhanced MR angiography- time of flight phase contrast A dv: Can be done without contrast Time-of-flight (non-contrast) MR angiogram, axial view

7. Intracranial circulation

8. CCA bifurcates at C4 vertebral body Complex course 7 segments and 3 genu Anterior circulation

9. Internal Carotid artery Seven segments, C1–C7 C1- Cervical segment C2- Petrous segment C3- Lacerum segment C4- Cavernous segment C5- Clinoid segment C6- Ophthalmic segment C7- Communicating segment

10. Cervical segment Course – crosses behind and medial to ECA N o named branches ICA ECA

11. Petrous segment C2 ICA –intraosseous enters carotid canal in petrous temporal bone. exits at petrous apex Branches • Vidian artery (artery of pterygoid canal) anastomoses with external carotid artery (ECA) • Caroticotympanic artery (supplies middle ear)

12. Axial CT Posterior genu as it courses anteromedially into the cavernous sinus ICA courses along the basisphenoid bone Through cavernous sinus proper turns superiorly Form grooves under anterior clinoid process Curve upwards towards dural ring Enter subarachnoid space Posterior genu Carotid sulcus Anterior genu Cavernous ICA

13. Cavernous ICA Major branches - Meningohypophyseal trunk (arises from posterior genu, supplies pituitary, tentorium and clival dura) - Inferolateral trunk arises from horizontal segment, supplies cavernous sinus (CS) dura / cranial nerves;

14. Clinoid segment C5 Between proximal , distal dural rings of cavernous sinus Ends as ICA enters subarachnoid space near anterior clinoid process No important branches

15. Ophthalmic segment C6 Extends from distal dural ring at superior clinoid to just below posterior communicating artery (PCOM) origin Branches – Ophthalmic artery Superior hypophyseal artery Anterior clinoid process C6

16. Normal ICA variants Aberrant ICA Persistent stapedial artery Embryonic carotid-basilar anastomosis.

17. Aberrant ICA Involution of normal cervical ICA Enter through posterior wall of middle ear cavity and crosses MEC and joins horizontal segment Can present as a retrotympanic vascular mass

18. Persistent stapedial artery embryonic stapedial artery persists postnatally arises from the C2 (petrous) ICA PSA passes through the stapes footplate and doubles the size of the anterior (tympanic) facial nerve segment M MA arises from PSA

19. Persistent embryonic carotid-basilar anastomosis.

20. Variants – Persistent Trigeminal Artery In utero – embryonic trigeminal artery supplies basilar artery before the PCOM and vertebral artery develops trident shape on lateral DSA

21. Increased incidence of intracranial aneurysms / malformations Increased importance in transphenoidal surgery

22. CIRCLE OF WILLIS Ring of vessels Connects the anterior and posterior circulation Important source of collateral circulation

23. Normal MR Angiogram

24. Anterior cerebral artery Medial branch of supraclinoid ICA Runs in interhemispheric fissure 3 segments

25. Three segments A1 (horizontal): origin from the ICA to the anterior communicating artery (ACOM). ~14 mm in length A2 (vertical): from ACOM to the bifurcation. A3 (cortical branches): distal to the bifurcation.

26. ACA TERRITORY Anterior two-thirds of the medial surface of the hemisphere Small wedge along the inferomedial frontal lobe Cortex over the top of the hemisphere vertex

27. Segments M1: horizontal segment from the origin to bifurcation/trifurcation M2 :  insular segment from bi/(tri)furcation to circular sulcus of insula where it makes hairpin bend to continue as M3 M3:  opercular branches (those within the Sylvian fissure); M4:  cortical segment Middle cerebral artery

28. MCA territories majority of the lateral surface of the hemisphere except the superior portion of the parietal lobe (via ACA) and the inferior portion of the temporal lobe and occipital lobe (via PCA).

29. Posterior cerebral artery P1:  from it origin at the termination of the basilar artery to posterior communicating artery (PCOM), within interpeduncular cistern. P2:  from the PCOM around the mid-brain to ambient segment P3:  segment with the quadrigeminal cistern P4 :  cortical segment

30. MR Angiography

31. The PCA territory occipital lobe posterior third of the medial and the posterolateral surfaces of the hemisphere inferior surface of the temporal lobe

32. Variants hypoplasia of one or both PCOM ~30% hypoplastic/absent A1 segment of ACA ~15% absent or fenestrated ACOM ~12.5% origin of PCA from the ICA with absent/hypoplastic P1 segment (fetal PCOM) ~20% infundibular dilatations of the PCOM origin ~10% (range 5-15%)

33. Duplicated ACOM Fenestrated ACOM

34. Fetal origin of posterior cerebral artery The posterior cerebral artery (PCA) arises directly from internal carotid artery (ICA) on right side. The right P1 segment is hypoplastic.

35. Vertebrobasilar system V1 (EXTRAOSSEOUS) SEGMENT: enters the C6 transverse foramen V2 (FORAMINAL) SEGMENT: V3 (EXTRASPINAL) SEGMENT. VA exits the C1 transverse foramen V4 (INTRADURAL) SEGMENT. VA becomes intradural, it courses superomedially behind the clivus and in front of the medulla anterior and posterior spinal arteries medullary perforating branches. PICA

36. Basilar artery At pontomedullary junction Terminates in the interpeduncular cistern give 2 PCAs AICA SCA Pontine Labyrinthine

37. Territory Cerebellum, midbrain, posterior thalami, occipital lobes, most of the inferior and posterolateral surfaces of the temporal lobe, and upper cervical spinal cord

38. Normally left vertebral artery is dominant 50 % Origin from aortic arch No connection with basilar artery Fenestration / Partial duplication Variants

39. Normal Venous Anatomy Two major components Dural venous sinuses Cerebral veins S uperficial Deep

40. Dural sinuses Superficial cerebral veins (Sup, middle, inf ) drain in to sagittal sinus CSF drains into it via arachnoid granulations The two TSs are frequently asymmetric, with the right side typically larger than the left. Hypoplastic and even atretic segments are common

41. Arachnoid granulations Superficial cortical veins

42. Cavernous Sinus irregularly shaped, heavily trabeculated/compartmentalized venous sinuses lie along the sides of the sella turcica T ributaries draining into the CSs Superior/inferior ophthalmic veins Sphenoparietal sinuses

43. Deep system of veins Internal cerebral veins- Anterior and middle cerebral veins join to form basal vein. (1) medullary veins (2) subependymal veins (3) deep paramedian veins Great cerebellar vein a/k/a vein of galen .

44. Internal carotid angiogram

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