3. 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,
4. 5-6 mm Embryo
• PCOM develops
• TA, OA, HA regress & obliterate
• PTA supplies the caudal part of the neural arteries
until 7-12 mm
5. 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;
7. • 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)
8. 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)
27. 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
32. • 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
