Technical feasibility and histopathologic studies of poly (N-isopropylacrylamide) as a non-adhesive embolic agent in swine rete mirabile.
BACKGROUND
Non-adhesive liquid embolic agents are increasingly gaining importance in the embolization of cerebral arteriovenous malformations (AVMs). We investigated the use of poly (N-isopropylacrylamide) (PNIPAM) as a non-adhesive embolic agent in swine rete mirabile.


METHODS
The PNIPAM hydrogel was mixed with iohexol and embolization was performed in swine rete mirabile in 30 animals. The microcatheter was examined after embolization. Follow-up angiography was performed for embolic efficacy after embolization. Embolized retia were examined histopathologically, and the alterations of inside rete and surrounding tissue were observed.


RESULTS
The copolymer hydrogel was used for rete embolization in 30 swine, 28 swine survived the procedure, 2 swine died, 1 swine died of cerebrum infarction and the other died of embolic agent reflux into the occipital artery. The inside wall of the microcatheter was smooth, without copolymer adhering to it. Follow-up angiography was performed in 22 swine, there was no rete recanalization in 20 swine and partial rete recanalization in 2 swine because of the trunk embolization of ascending pharyngeal arteries. Histopathologically, the copolymer was found diffused into vessels of 100 - 150 microm in diameter. In acute group, neutrophils scattered surrounding the copolymer and endothelial integrity was observed, without endothelial denuding and necrosis. In subacute and chronic groups, the copolymer was found inside retia, a few mononuclear cells and eosinocytes scattered inside and surrounding it. The muscular layer was loosened with most muscular nuclei degraded.


CONCLUSIONS
Experimental rete embolization with PNIPAM, made radiopaque with iohexol, is technically feasible in swine. Because of its properties, PNIPAM has great potential as a therapeutic non-adhesive embolic agent.
Sheng
Xi-zhong
XZ
Department of Neurosurgery, Shandong Provincial Qianfoshan Hospital, Jinan 250014, China. xizhongsheng@vip.sina.com
Liu
Zuo-qin
ZQ
Wu
Le-bin
LB
Tang
Jun
J
Zhao
Cheng-ru
CR
Kong
Ling-bin
LB
Wang
Qin
Q
Wang
Chuan-dong
CD
D000180:Acrylic Resins; D000818:Animals; D004621:Embolization, Therapeutic / Q000379:methods*; D002538:Intracranial Arteriovenous Malformations / Q000628:therapy*; D013552:Swine
D000180:Acrylic Resins; C052970:poly-N-isopropylacrylamide