| No | Kind of vascular variant | Target artery (side/mode of the origin) | CCA absence | Left side | Right side | Bilateral | References |
| 1 | Accessory vessel | Lateral IThA | | [45] | | 2 | Additional absence | Left ACA | [61] | | | Left OPhA | [52] | | | Right ACA | | [22] | | BT | | [9, 18, 34, 36, 39, 45, 73–75, 77–79, 81] | [80] | Left ECA | [18, 52, 53, 71, 83] | | | Left ICA | [18, 52, 53, 71, 83] | | | Left SA | [71] | [74, 75] | | Left VA | [71] | | | Right ECA | | [31, 74] | | Right ICA | | [31, 74] | | Right TT | | [19] | | 3 | Arterial loop | Left ICA | [16] | | | | | Right ECA/ICA | | | [64] | 4 | Diverticulum at the origin | Left SA | | [9, 39, 45, 73–75, 77, 79] | | 5 | Ectasia | Left PCoA | [52, 53] | | | Left SA | [3] | | | Left VA | [54] | [29] | | Right VA | | [29] | | 6 | Elongation | BT | | [19, 84] | | 7 | Hypoplasia | Left A1 | [42, 58] | | | Right A1 | | [24] | | Left ECA | [54] | | | Left ICA | [54, 61, 62] | | | Right ICA | | [5, 22, 29] | | Right VA | [58] | | | 8 | Low bifurcation | Right CCA | [1, 68] | | | 9 | Persistence of the primitive CVBA | Left PPIA (type 2) | [54, 59] | | | PPIA | [41] | | | Left PTAV | [58] | [29] | | 10 | Persistence of the primitive vein | Left SVC | | [45] | | 11 | Short trunk | BT | [6] | | | 12 | Tortuosity | Anastomotic vessels | | [29] | | BT | | [84] | | Left ICA | [42, 61, 62, 85, 86] | | | Left SA | [33] | | | RCAA | | [79] | | Right ICA | | [14] | | Right SA | [83] | | | 13 | Unusual vessel | DAA | | | [40] | LCAA | [33, 70] | | | LIA | | [80] | | RCAA | [71, 72] | [9, 34, 36, 39, 45, 73–81] | | 14 | Variable course | Descending aorta | [33] | | | Left SA | | [34, 73] | | Right VA | | [14] | | 15 | Variable mode of the origin | Fetal origin of the right PCoA | [58] | | | Common origin of the BT and left CCA | | [7] | | Common origin of the BT and left ECA | [68] | | | Common origin of the left ICA and left SA | [67] | | | Common origin of the left ICA and left VA | [87] | | [38] | Distal origin of the right VA | | [17] | | High origin of the right SA | | | [64] | Origin of the right ICA proximally to the right ECA | | [21, 25] | | 16 | Variable vascular source: branch(es) | Ascending aorta: left CCA | | [74, 75, 77, 81] | | Ascending aorta: right ECA | | [77] | | BT: left ECA | | | [65, 69] | BT: left VA | [10] | | | BT: right CcT | | [7] | | BT: right ECA | | [5, 14, 15, 17, 18] | | BT: right ECA and right ICA | | [7, 20–29, 66, 84] | [38, 65, 69] | BT: right ICA | | | [55] | BT: right VA | | [7] | | Descending aorta: left VA | [83] | | | Descending aorta: left SA | [82, 83] | [9, 39, 75] | | Descending aorta: right SA | | [75] | | DAA: left and right ECAs and ICAs | | | [40] | LIA: left CCA and SA / | | [80] | | Left MCA: left OPhA | [53] | | | Left PCoA: left MCA | [53] | | | Left PPIA: left ECA and ICA | [54] | | | LCAA: left ECA and left ICA | [33, 70] | | | NAA: left ECA and ICA | | | [55] | NAA: left ICA | | | [38, 65, 69] | NAA: left VA | | [26] | [38, 65] | NAA: right ECA | | | [55] | NAA: right ECA and right ICA | | [18] | | NAA: right ICA | | [13, 18] | | NAA: right VA | [71] | | | RCAA: right ECA and right ICA | [71, 72] | [34, 36, 45, 73, 75–81] | | RCAA: right SA | | [9, 34, 36, 39, 73, 74, 77–80] | | RCAA: right VA | | [78] | | Right ECA: right IThA | | [19] | | Right ICA: right APhA | | [19] | | Right SA: right ICA | | [5, 14, 15, 17, 22] | |
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aVascular variants are only alphabeticaly listed and do not indicate the number of cases, because they were multiple in some of the cases.Note: Some references are cited as follow: Malacarne [ 40], cited by Andrews and Howard, [ 6]; Gottschau [ 41], Smirnov [ 85], and Schmeidel [ 86], cited by Bryan et al. [ 43]; Kosinski [ 66], cited by Boyd [ 14]; Chang et al. [ 76], cited by Shuford et al. [ 39]; and Johnson et al. [ 87], cited by Dahn et al. [ 16]. IThA internal thoracic artery, ACA anterior cerebral artery, OPhA ophthalmic artery, BT brachiocephalic trunk, ECA external carotid artery, ICA internal carotid artery, SA subclavian artery, VA vertebral artery, TT thyrocervical trunk, PCoA posterior communicating artery, Al pre-communicating part of the ACA, PPIA persistent proatlantal intersegmental artery, PTAV persistent trigeminal artery variant, SVC superior vena cava, RCAA right-sided cervical aortic arch, DAA double aortic arch, LCAA left-sided cervical aortic arch, LIA left innominate artery, CcT costocervical trunk, MCA middle cerebral artery, NAA normal aortic arch, APhA ascending pharyngeal artery. |