Absence of Brain Parenchymal Damage following Intravascular Injection of Polytetrafluoroethylene Paste

Objective: Polytetrafluoroethylene (PTFE) paste has been used for over 30 years to treat urinary incontinence and for 14 years to treat vesicoureteral reflux with little reported morbidity. Some investigators have been concerned by the use of PTFE as the implanted substance, because migration of PTFE particles from the site of injection in the periurethral and periureteral regions to the lungs and brain has been reported in animal studies. We injected PTFE paste intravascularly in dogs in order to investigate its effect on brain parenchyma. Methods: A total of 12 mongrel dogs, weighing 11.5–17.5 kg, were divided into four groups. Group 1 (n = 3): injection of 0.5 ml of PTFE paste suspended in 50 ml of saline into a peripheral vein once a week for 4 weeks. Group 2 (n = 3): injection of 50 ml of saline into a peripheral vein once a week for 4 weeks as controls. Group 3 (n = 3): one injection of 0.1 ml of PTFE paste suspended in 20 ml of saline into the right carotid artery. Group 4 (n = 3): one injection of 20 ml of saline into the right carotid artery as controls. After an interval of 6 months, all animals were sacrificed and the lungs and brain removed. Brain from 1 animal in each group was dissolved in sodium hypochlorite solution, the resulting organ suspension was centrifuged, and the smear preparations of the precipitate examined by polarized light microscopy, scanning electron microscopy, and X-ray microanalysis. Brains from 2 animals in each group were fixed in formalin solutions, 6-µm sections were cut and stained with haematoxylin and eosin, Cajal stain for Purkinje fibre, and Luxol fast blue stain for myelin, and glial fibrillary acidic protein immunohistochemistry was carried for astrocytes using monoclonal mouse anti-GFAP (glial fibrillary acidic protein) at a dilution of 1:50 with an avidin-biotin-peroxidase complex method. Results: PTFE particles were seen in the cerebral vessels in only those animals who had PTFE injected into the right carotid artery. The haematoxylin and eosin staining showed PTFE particles in vessels with focal foreign-body reaction, but no infarction. Luxol fast blue staining showed no demyelination around vessels containing the particles and the parenchyma. Cajal staining demonstrated no abnormality of nerve fibres, and there was no astrocytosis using GFAP immunohistochemical staining. Conclusions: Our findings indicate that following intravenous injection, there was no evidence of migration of PTFE to the brain. Small q