1. Cerebrovascular Embryology October 6, 2000
Brain School
Resident: Dr. Charles Matouk
Supervisor: Dr. Chris Wallace

2. Primitive Aortic Arches
Key Points
Cephalic location of primitive heart
6 pairs of primitive aortic arches
Thoracic migration of heart and step-wise arch regression

3. Primitive Aortic Arches
Major Events
Regression of dorsal aorta between 3rd and 4th arches
Derivation of subclavian arteries from 6th intersegmental arteries
Attenuation of R 4th aortic arch

4. 4-mm Fetal Stage 1st arch – involution and mandibular artery remnant
2nd arch – involution and hyoid artery remnant
3rd arch – precursor of ICA and ECA

5. 4-mm Fetal Stage Cranial division of primitive ICA – primitive ACA
Caudal division – precursor of PComA
ACA is the direct embryonic continuation of ICA, not MCA!!!

6. 4-mm Fetal Stage
In hindbrain, arterial vasculature defined by paired, separate longitundinal nerual plexi
Supplied by anastomotic branches of primitive ICA and C1 segmental artery, and others

7. Embryonic Carotid-Basilar Anastomoses
Persistent trigeminal artery
Otic artery
Hypoglossal artery
Proatlantal intersegmental artery

8. 5-6-mm Fetal Stage
Ventral pharnygeal artery (precursor of proximal ECA vasculature) now prominent
Caudal division of ICA forms anastomoses with cranial-end of bilateral longitudinal neural arteries

9. 7-12-mm Fetal Stage
Ventral pharyngeal system more extensive with identifiable branches (precursor of proximal ECA)
Hyoid artery (precursor of upper portion of ECA)

10. 7-12-mm Fetal Stage
Vertebral arteries formed by coalescence of longitudinal anastomoses between cervical segmental arteries

11. Drapkin AJ. The double lumen sign: a pathognomonic sign of arterial dissection? Diagnostic Neuroradiology 42: ;2000.

12. 12-14-mm Fetal Stage
Plexiform anastomosis between ACAs evolve into AComA

13. 16-18-mm Fetal Stage
Stapedial artery (branch of hyoid artery) at zenith of development)
Its development defines distal ECA circulation and middle meningeal artery.

14. 16-18-mm Fetal Stage
Fate of stapedial artery … proximal trunk regression with annexation of territories by ventral pharnygeal trunk and ophthalmic arteries

15. Evolution of Primitive Ophthalmic Arteries
Ventral (from ACA) ophthalmic artery
Dorsal ophthalmic artery
When dorsal persists or is dominant, ophthalmic artery originates from cavernous segment of ICA

16. Evolution of Posterior Circulation
PCA arising from ICA, predominantly or exclusively, is described as being of ‘fetal origin’

17. Review

18. Review

19. Review

20. Review

21. References
Morris, P. Practical Angiography Williams & Wilkins, Baltimore, Maryland. Chapter 5, pp
Osborn, A. Diagnostic Neuroradiology Mosby, St. Louis, Missouri. Chapter 6, pp
Moore KL and Persaud TVN W.B. Saunders Company, Philadelphia, Pennsylvania. Chapter