Tissue reactions induced by different embolising agents in cerebral arteriovenous malformations: a histopathological follow-up

Aims: Comparative histopathological analysis was performed in 47 incompletely embolised and resected cerebral arteriovenous malformations ( AVMs). Methods: Thirty-three AVMs were embolised with n-butylcyanoacrylate ( NBCA), four with iso-butyl-cyanoacrylate ( IBCA), seven with polyvinyl alcohol particles ( PVA), one with a fibrin mixture, one with silicon pellets, and one with microcatheter balloons. Maximum exposure time ( MET) of the embolising agent ( interval between embolisation and surgery) ranged from < 24 hours to 80 months. All AVMs were investigated regarding angionecrosis, angiofibrosis, acute inflammation, chronic inflammation, foreign-body reactions, vascular calcification, blood admixture to embolising cast, and capillary recanalisation within the AVMs. These parameters were correlated with MET, comparing different embolising agents, age, and sex. Results: A typical sequence of events depending on MET is observed in all embolised AVMs: acute inflammation with mural angionecrosis is soon replaced by prominent chronic granulomatous vasculitis, which remains stable and is detectable for a very long time, even in AVMs with a MET of more than 6 years. Conclusion: Capillary recanalisation is always present in incompletely embolised AVMs, detectable after 3 months of MET, irrespective of the embolising agent used. Age and sex does not influence pattern and time course of tissue lesions and recanalisation in incompletely embolised AVMs.