Origin–entry geometry and left-sided V1 vertebral artery tortuosity
A retrospective cross-sectional CTA study showing that V1 tortuosity is more pronounced on the left, rises with age, and is related to the geometry between vertebral artery origin and the relatively conserved transverse-foraminal entry.
Left V1 tortuosity is linked to an origin–entry mismatch, not to calibre-defined dominance.
The study found a stable left-sided predominance of tortuosity, strong age correlation, and a significant association with more cranial vertebral artery origins against a largely conserved C6 entry level.
Fifty bilateral CT angiograms
The study analysed both V1 segments in each patient to test bilateral asymmetry, geometric predictors, and the relation between tortuosity and vertebral artery dominance.
Patients
24 men and 26 women.
V1 segments
Both sides evaluated quantitatively.
Mean age
Years ± 15.5.
Bilateral C6 entry
The transverse foraminal entry level was highly conserved.
Left V1 is significantly more tortuous
The bilateral difference was robust by paired testing and was present in the large majority of patients.
Paired difference
Wilcoxon signed-rank test confirmed strong left-sided predominance.
Effect size
Cohen’s dz showed a substantial within-pair effect.
Direction
41 of 50 patients had a more tortuous left V1.
A cranial origin shortens the chord more than the path
This is the geometric argument proposed by the paper: when the VA originates more cranially but still enters the transverse foramen at a conserved C6 level, the straight-line distance contracts while the centreline remains relatively preserved, increasing the tortuosity index.
Age matters, calibre dominance does not
Tortuosity increased with age on both sides and with more cranial origins, but no association was detected between V1 tortuosity and calibre-defined vertebral artery dominance.
Age · left
Spearman correlation with left V1 TI.
Age · right
Spearman correlation with right V1 TI.
Dominance
No association between tortuosity and calibre-based dominance.