Silicone oil in the subarachnoidal space--a possible route to the brain?

Using this case report, we sought evidence that silicone oil may infiltrate the subarachnoidal space. Vitrectomy combined with silicone oil implantation was performed on the right eye of a 72-year-old woman. The silicone oil was removed 2 months later, because the patient had developed elevated intraocular pressure. The blind and painful eye was subsequently enucleated. By light microscopy, presumed silicone oil bubbles were identified in the optic nerve and the subarachnoidal space of the enucleated eye. These vacuoles were examined by energy-dispersive X-ray analysis (EDAX). In addition, in the vacuoles, immunohistochemistry was used to test for the presence of CD 68-positive macrophages. Silicone oil infiltration sites in the optic nerve, in the central retinal artery, and in the subarachnoidal space were located by light microscopy and confirmed by EDAX. CD 68-positive macrophages were found in the silicone-filled vacuoles. Silicone oil used for endotamponade may infiltrate the optic nerve and even the subarachnoidal space. This supports the assumption that silicone oil, under special circumstances, may even migrate into the brain.