Cerebrovascular EmbryologyOctober 6, 2000

Brain School

Resident: Dr. Charles Matouk

Supervisor: Dr. Chris Wallace

Primitive Aortic Arches

Key Points

1) Cephalic location of primitive heart

2) 6 pairs of primitive aortic arches

3) Thoracic migration of heart and step-wise arch regression

Primitive Aortic Arches

Major Events

1) Regression of dorsal aorta between 3rd and 4th arches

2) Derivation of subclavian arteries from 6th intersegmental arteries

3) Attenuation of R 4th aortic arch

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

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!!!

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

Embryonic Carotid-Basilar Anastomoses

1) Persistent trigeminal artery

2) Otic artery

3) Hypoglossal artery

4) Proatlantal intersegmental artery

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

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)

7-12-mm Fetal Stage

Vertebral arteries formed by coalescence of longitudinal anastomoses between cervical segmental arteries

Drapkin AJ. The double lumen sign: a pathognomonic sign of arterial dissection?

Diagnostic Neuroradiology 42:203-205;2000.

12-14-mm Fetal Stage

Plexiform anastomosis between ACAs evolve into AComA

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.

16-18-mm Fetal Stage

Fate of stapedial artery … proximal trunk regression with annexation of territories by ventral pharnygeal trunk and ophthalmic arteries

Evolution of Primitive Ophthalmic Arteries

1) Ventral (from ACA) ophthalmic artery

2) Dorsal ophthalmic artery

When dorsal persists or is dominant, ophthalmic artery originates from cavernous segment of ICA

Evolution of Posterior Circulation

PCA arising from ICA, predominantly or exclusively, is described as being of ‘fetal origin’

Review

Review

Review

Review

References

1. Morris, P. Practical Angiography. 1997. Williams & Wilkins, Baltimore, Maryland. Chapter 5, pp 89-98.

2. Osborn, A. Diagnostic Neuroradiology. 1994. Mosby, St. Louis, Missouri. Chapter 6, pp 117-153.

3. Moore KL and Persaud TVN. 1998. W.B. Saunders Company, Philadelphia, Pennsylvania. Chapter 349-403.