Blood supply of brain

ANATOMY

1. Blood supply of Brain Dr. Ajaya Jang Kunwar

2. Blood supply of Brain If blood supply stops - 10 sec – Unconscious If it continue to cease – irreversible damage starts at 4 min – completes in 10 min Brain consists of 2% of total body but Receives 20% cardiac output 20% total O2

3. Arterial supply of brain Brain is supplied by 2 sets of arteries A pair of Vertebral arteries A pair of Internal carotid arteries

4. Circle of Willis ( Circulus arteriosus ) Anteriorly: Anterior communicating & anterior cerebral arteries Posteriorly: Basilar artery dividing into 2 posterior cerebral arteries Laterally on either side: Posterior communicating artery connecting internal carotid with Posterior cerebral artery

5. Circle of Willis lies around the interpeduncular fossa

6. Equalizes blood flow to different parts of the brain. Little interchange of blood across right and left half due to equality of blood pressure. In case of occlusion, circle of willis acts as principal collateral channel. Functional Significance of Circle of Willis

7. Branches of cranial part of vertebral artery Anterior spinal artery Posterior spinal Posterior inferior cerebellar (Largest branch) Meningeal arteries Supplies the dura matter of posterior cranial fossa Medullary arteries Supplies medulla oblongata

8. Branches of Basilar artery Pontine arteries Anterior inferior cerebellar artery Labyrinthine artery Superior cerebellar artery Posterior cerebral artery Anterior temporal Posterior temporal Parieto -occipital Calcarine artery

9. Branches of Internal carotid artery Ophthalmic artery Posterior communicating Anterior choroidal Supplies choroid plexus of interior horn of Lateral ventricle (artery of cerebral thrombosis) Anterior cerebral artery Middle cerebral artery Carries 30% of carotid blood Hypophyseal arteries

10. Branching pattern of cerebral arteries Cortical branches Central branches (Perforating arteries) Choroidal arteries

11. Cortical branches Supplies outer portion of cerebrum. Derived from ant, middle & post cerebral arteries. Ramify in the piamater & form freely anastomosing superficial plexuses. Two set of br’s Short - Supplies cortical grey matter Long - Supplies white matter End arteries: do not anastomose with other arteries.

12. Central branches (Striate arteries) Derived from circle of willis Penetrate the base of the brain Supplies: Diencephalon, Basal nuclei, Internal capsule 4 groups Anteromedial : From Ant. Cerebral & Ant. Com. Art. Anterolateral : From mid. Cerebral Posteromedial : From Post. Cerebral & Post. Com. Art. Posterolateral : Posterior cerebral Central br’s are end arteries

13. Choroidal Arteries Anterior choroidal artery From Int. Carotid art: choroid plexus of Inf. Horn of Lateral ventricle Posterior choroidal artery From Post. Cerebral art: choroid plexus of 3 rd and lateral ventricle.

14. Superolateral surface Most of surface (2/3) – Middle cerebral artery A small strip c. 2.5 cm along superomedial border upto parieto -occipital sulcus – Anterior cerebral artery Occipital lobe + inferior part of temporal lobe (excluding – temporal pole – Posterior cerebral artery

15. Occlusion of middle cerebral artery may lead to Contralateral hemiplegia , hemianaesthesia (mainly face & arm) – due to invl . Of most of primary motor and sensory areas Apasia (Loss of speech) – if dominant hemisphere involved due to inv. of motor & sensory speech area Contralateral homonymous hemianopia (right or left half of vision both sides lost) – invl . of optic radiation

16. Motor Homunculus

17. Sensory Homunculus

18. Medial Surface Most of med. surface upto parieto -occipital sulcus (2/3) Anterior cerebral artery Temporal pole Middle cerebral artery Rest of temporal lobe + Occipital lobe Posterior cerebral artery

19. Occlusion of anterior cerebral artery leads to Contralateral hemiparesis, hemianaesthia (mainly leg & foot) Due to Invol . of upper part of prim. motor and prim. sensory areas and paracentral lobule Inability to identify object correctly Due to invl . of superior parietal lobule Apathy and personality changes Invl . of part of frontal lobe

20. Inferior surface Most of inferior surface except temporal pole Posterior cerebral artery Temporal pole + lateral part of orbital surface of frontal lobe Middle cerebral artery Medial part of orbital surface of frontal lobe Anterior cerebral artery

21. Occlusion of posterior cerebral may lead to Contralateral homonymous hemianopia : – inv. Of visual cortex with some degree of macular sparing (Since occipital pole also has alternative supply from middle cerebral artery )

22. Corpus striatum and internal capsule: B y medial and lateral striate central branch of middle cerebral artery. Thalamus: B y br of post communicating, basilar and post cerebral arteries. Midbrain: B y post cerebral, superior cerebellar and basilar arteries. Blood supply of other parts of Brain

23. Pons: By pontine br. Of basilar and ant. inf. and sup c erebellar arteries. Medulla: By vertebral, ant and post spinal, post inferior cerebellar and basilar arteries. N.B. The brain stem, cerebellum and occipital lobe are supplied by the vertebrobasilar system .

24. Cerebellum Superior cerebellar artery Anterior inferior cerebellar Posterior inferior cerebellar

25. Venous drainage of brain Thin walled. Absence of muscular layer No valves Venous return of brain doesn’t follow the arterial pattern. Veins of brain are Cerebral (Superficial or external and Deep veins) Cerebellar Veins of brainstem

26. External cerebral veins. Superior cerebral veins. Middle cerebral vein. Superficial and Deep Inferior cerebral veins Other veins Deep cerebral, Anterior cerebral and Striate veins form the basal vein.

27. Inferior cerebral and other veins in base of brain

28. Internal cerebral veins 2 int. cerebral veins on either side of midline in tela choroidea of 3 rd ventricle Formed by the union of Septal Thalamostriate Choroidal vein at the interventricular foramen Joins to form great cerebral vein (of Galen) - Empties into straight sinus.

29. Veins of midbrain & cerebellum also join the great cerebreal vein (of Galen)

30. Blood brain barrier Tight junction between the endothelial cells Basement membrane of endothelial cells Foot process of Astrocytes

31. Arterial supply of spinal cord Anterior spinal artery. Two p osterior spinal a rteries . Radicular or segmental arteries.

32. ARTERIAL SUPPLY 2/3 1/3

33. A single Y - shaped artery. Arises from : Vertebral artery at the level of the medulla. Supplies the cord at the Cervical Level. It is most vulnerable in the anterior part of the cord particularly in the Thoracic Segment. ANTERIOR SPINAL ARTERY

34. Two arteries. Arise from Vertebral Or Posterior Inferior Cerebellar arteries. Spinal Arteries (Anterior &Posterior) are Insufficient alone to supply the cord Below the Cervical Level . POSTERIOR SPINAL ARTERIES

35. Origin from following arteries : 1. Deep cervical 2. Ascending cervical 3. Intercostal . 4. Lumbar. They share in the arterial supply of the cord Below the Cervical Level. They Anastomose freely with the Spinal Arteries. RADICULAR ARTERIES

36. Artery of Adamkiewicz . It may arise from: Intercostal or Lumbar arteries (usually T1 or T11). It supplies Lower half of the spinal cord ( T8 –L3 ). These are Vulnerable Segments. Occlusion of the artery may cause Muscle weakness and Paralysis. GREAT RADICULAR ARTERY

37. Venous drainage of spinal cord 4 channels drain into vertebral, posterior intercostal , lumbar and lateral sacral veins.