The Persistent Fetal Carotid-Vertebral

anastomosis

Persistent fetal anastomosis

• Persistent trigeminal artery• Persistent otic artery• Persistent Hypoglossal artery• Persistent proatlantal artery

4-5 mm Embryo

A) Bilateral longitudinal neural arteries (LNA, arrows) supply hindbrain,B) Bilateral LNA are supplied by carotid arteries {via trigeminal artery (TA), otic artery

(OA), hypoglossal artery (HA), proatlantal intersegmental artery (PA)} & cervical intersegemental arteries (CIA)

* AA= forth aortic arch, DAo=dorsal aorta, VAo= Ventral aorta,

5-6 mm Embryo

• PCOM develops• TA, OA, HA regress & obliterate• PTA supplies the caudal part of the neural arteries until 7-12 mm

7-12 mm Embryo

A) Vertebral artery (VA) develops through the transverse anastomoses between adjacent cervical intersegmental arteries and distal part of the proatlantal artery becomes the horizontal portion of the vertebral artery (arrowheads) while proximal part regresses completely. Failure of this regression results as persistent proatlantal artery (dashed lines).

B)At this stage of embryo TA, OA, and HA has disappeared after development of posterior communicating artery (PCA). AA, fourth aortic arch;

Persistent trigeminal artery

• The most common variant• Connect between cavernous ICA & BA• Intrasellar course Vs Parasellar course• Associated with vascular anomaly 24%• Associated with aneurysm ? (4-14%)• Can cause trigeminal neuralgia

Persistent trigeminal artery (PTA)

Three types of PTA• Saltzman type I

• Cavernous ICA to basilar • Supplies both PCA & SCA• PCOM absent/hypoplastic

• Saltzman type II• PCOM present and PCOM supplies to PCAs• Join basilar between SCA & AICA

• Saltzman type III• Trigeminal artery joins to a cerebellar artery (AICA most commonly)

Persistent trigeminal artery (PTA)

Parasellar course of PTA

Parasellar course of PTA

Intrasellar course of PTA

Persistent trigeminal artery (Saltzman type I)

Persistent trigeminal artery (Saltzman type I)

TAU sign

Persistent trigeminal artery (Saltzman type II)

Persistent trigeminal artery (Saltzman type III)

• AICA is the most common• Not associated with basilar hypoplasia

Persistent trigeminal artery (Saltzman type III)

PTA (Type I) & Aneurysm

Persistent otic artery

Persistent Otic Artery

Persistent Otic Artery

• Arising from petrous ICA• Run through internal auditory canal• Connect to proximal basilar artery

Persistent Otic Artery

Persistent Otic Artery

Persistent Otic Artery

Persistent hypoglossal artery

Persistent Hypoglossal artery

• Second most common variant• Rises from C1 or C1-C2 level of ICA• Enter skull via hypoglossal canal• Lack horizontal curve unlike proatlantal• Vertebral a. may be aplastic or hypoplastic• Can cause glossopharyngeal neuralgia or hypoglossal nerve palsy

Persistent Hypoglossal artery

Persistent Hypoglossal artery

Red= PHA, Pink= Coil mass, Blue = Sigmoid sinus

Bilateral persistent hypoglossal arteries (PHA)

C1-C2 level

Thru Hypoglossal canals

Persistent proatlantal artery (PPA)

• Rare• Two type

• Type 1 PPA from ICA, arising at C2-C3 vertebral level

• Type 2 PPA from ECA

• Usual joins vertebral artery at V3 segment, enter skull via foramen magnum

• Associated with aneurysm, ICH, Syncope, ischemia, tinnitus

Persistent proatlantal artery

Persistent proatlantal artery

Rising from C3, enter skull via foramen magnum

PPA type I

Bilateral PPA type II

Bilateral proatlantal arteries (white arrow) originating from ECA Basilar artery (Yellow arrow)

PPA Type II

Reference• AJR 1999;172:1427-1432 0361-803X199/1725-1427• http://radiologic-technology.blogspot.com/2012/11/persistent-hypoglossal-artery.html• http://www.ijri.org/viewimage.asp?img=IndianJRadiolImaging_2010_20_4_258_73534_u4.jp

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