The contribution of wall shear stress insult to the growth of small unruptured cerebral aneurysms in longitudinal 3D-TOF-MRA.

OBJECTIVE

Aneurysm growth is a risk factor for rupture, however the detailed mechanism remains unclear. The present study was performed to identify whether hemodynamic insult could prompt small unruptured aneurysms to grow.

METHODS

Six pairs of unruptured small (<5 mm) cerebral aneurysms from patients followed with longitudinally three-dimensional MR imaging were selected and divided into an angiographic confirmed enlarged group (with >50% volume increase; n = 6) and an angiographic stable group (with ±10% volume changes; n = 6). Patient-specific computational fluid dynamic models were created and run under pulsatile flow conditions. Reverse reconstruction technique was used to simulate the status of before aneurysm generation. Relevant hemodynamic variables were calculated and compared between the two groups.

RESULTS

In the enlarged group, wall shear stress (WSS) decreased from aneurysm neck to dome, whereas WSS at the aneurysm neck (58.68 ± 34.45 Pa) and body (52.68 ± 46.37 Pa) was significantly higher than the stable group (neck: 36.83 ± 18.20 Pa and body: 30.77 ± 18.85 Pa) (P < .05). WSS decreased at the neck, body, and dome and flow patent became stable after aneurysm growth (P < .05). Reverse reconstruction revealed an elevated WSS at the site of aneurysm formation compared with other sites in the parent artery, and WSS at the formation site significantly decreased after aneurysm growth and further enlargement (P < .05).

CONCLUSION

Local elevated WSS to the arterial wall contributed to cerebral aneurysm generation, whereas turbulent flow patterns and elevated WSS at the aneurysm neck and body worked together to result in further growth of small aneurysms.