Introduction: Patients with ICASD form various degrees of collateralization. However, those collaterals fail over time contributing to symptom progression. Indirect revascularization via encephaloduroarteriosynangiosis (EDAS) establishes collateral flow through new vessels formed from external carotid branches in both moyamoya disease (MMD) and non-moyamoya (NM) ICASD. We hypothesize that the EDAS neovascularization differs in terms of angioarchitecture when compared to spontaneously formed collaterals in ICASD.
Methods: We analyze pre and post-operative digital subtraction angiograms (DSA) of patients enrolled in a prospective trial of EDAS surgery using ImageJ software (http://imagej.nih.gov/ij). Angioarchitectural differences between innate and post-EDAS collaterals were evaluated by comparing their branching angioscore (BA) and artery tortuosity index (ATI).
Results: Images from 26 patients, ages 4 to 84 (mean: 37 SD+/-19.5) were evaluated. Patients included 13 MMD and 13 NM-ICASD. Postoperative mean DSA time was 14 months. Post-EDAS collaterals had significantly higher BA and lower ATI than innate collaterals (BA: 9.8 vs. 5.5 and ATI 110 vs. 167 [p<0.001] respectively). Subgroup analyses for patients with MMD and NM-MMD demonstrated the same pattern with higher BA for post-EDAS collaterals and lower ATI for innate collaterals (MMD: BA: 9.6 vs. 5.2, and ATI 107.7 vs.176.5, NM-ICASD: BA: 9.9 vs. 5.8, and ATI: 153.7 vs.115.4 p=0.01). Type of ICASD, age, or time after angiography did not affect the indexes.
Conclusions: Collaterals formed after EDAS differ in angioarchitecture to innate collaterals in MMD and NM-ICASD. Morphological differences are consistent with two distinct mechanisms of vessel formation: innate collaterals formed by arteriogenesis display high tortuosity and low branching as expected by a shear stress process acting on pre-existing conduits. Conversely, post-EDAS collaterals have higher branching and lower tortuosity as expected in a process of angiogenesis in which collaterals form through sprouting and splitting from the donor vessels.
Patient Care: This research will lead to a better understanding of the mechanisms of vessel formation and how they relate to the failure or success of these vessels
Learning Objectives: By the conclusion of this session, participants should be able to: 1) Recognize the variation in architecture of different types of collateral vessels, 2) Discuss, in small groups how the difference in angioarchitecture may relate to the failure or success of the collaterals 3) Identify the different mechanisms of vessel formation