Normal Anatomical Features and Variations of the Vertebrobasilar Circulation and Its Branches: An Analysis with 64-Detector Row CT and 3T MR Angiographies

Table 2

Variations of the vertebrobasilar circulation.

Types of variation	CTA	MRA	Total
Normal anatomy	26	21	47
Agenesis of right PICA	19	5	24
Agenesis of left PICA	9	6	15
Agenesis of right AICA and left PICA	2	7	9
Agenesis of right and left AICA	2	7	9
Agenesis of left AICA	2	7	9
Agenesis of right AICA	4	2	6
Agenesis of right PICA and left AICA	3	2	5
Agenesis of right and left PICA	2	2	4
Right PICA originating from basilar artery	0	3	3
Right PICA originating from basilar artery and agenesis of left AICA	0	1	1
Isolated fetal origin of the PCA*	2	1	3
Total	71	64	135

CTA: computed tomography angiography, MRA: magnetic resonance angiography, PICA: posterior inferior cerebellar artery, AICA: anterior inferior cerebellar artery, and PCA: posterior cerebral artery.
*The other 11 cases of fetal origin of the PCA were accompanied to agenesis of PICA and/or AICA.