WP Anatomy
Angiographic analysis showed anatomical variants of WP in:
- 21 patients (28%) in anterior circulation (Figure 4)
- 48 patients (67%) in posterior circulation (Figure 5)
Afterwards 48 patients with variants in posterior circulation were classified in 3 groups depending on dominance:
- Symmetric: 25
- Right dominance: 9
- Left Dominance: 16
Interhemispheric asymmetries of flow with ASL
Arterial spin labeling (ASL) is a non-invasive perfusion technique,
which gives us quantitative information of cerebral blood flow.
It’s been widely demonstrated its utility in different pathologies of nervous system (Figure 6),
such as:
– Epilepsy: A decreased CBF in temporal mesial sclerosis and dysplasias have been observed,
a finding that has been correlated with a hypometabolism in PET studies and that could help us in the search of an epiloptogenic focus.
– High-grade tumors: ASL shows a high CBF that correlates with an also high cerebral blood volume in perfusion studies with intravenous contrast.
– Vascular pathologies: ASL could help us in detecting small arteriovenous malformations,
which are associated with an increased CBF.
Also in some cases of ischemia or hemodynamic compromise,
in which there will be a decreased CBF.
We visualized intehemispheric asymmetries of flow in posterior system in 19 patients (25 %),
16 of which presented anatomical variants (Figure 7).
We explain this finding due to a decreased CBF in posterior system irrigated from a fetal-type posterior cerebral artery (Figures 8,
9 and 10).
Quantitative analysis of ASL
Finally me measured quantitatively the interhemispheric asymmetries of ASL in the 3 groups,
observing differences of flow up to 13-20% in those patients who presented a fetal origin of the posterior circulation (Figure 11).
These asymmetries were more evident in occipital lobes (Figure 12).