LAUSR

A 60-year-old woman with history of type 2 diabetes mellitus, chronic kidney disease (CKD) and hypertension presented to the emergency department with 1 day of pressure like headache. Her vital signs along with the physical and neurological examination were all unremarkable, except for bilateral blindness. She had a complicated ophthalmological history of bilateral glaucoma, cataracts, and complex bilateral retinal detachment, treated approximately 1 year before, with silicon oil injection. Noncontrast head computed tomography (CT) was obtained that revealed small lentiform foci of increased density in the subependymal regions of the anterior aspect of each lateral ventricle, suggesting small focal hemorrhages (Fig, white arrows). There were also concerns for a thrombosed anterior cerebral artery (ACA) aneurysm. The patient underwent cerebral angiogram that was negative for aneurysms or any other vascular malformations, only showing diffuse intracranial atherosclerosis. Upon further discussion with neuro radiology, it was determined that what was seen as possible intraventricular hemorrhage (IVH), was in fact intracranial migration of intraocular silicone oil that had been used to treat the patient’s retinal detachment in the past. The patient was discharged home, asymptomatic, and with advice to follow up with ophthalmology. Silicone oil is an inert substance used as intraocular tamponade for retinal detachment. Intracranial migration of silicone oil has been suggested to happen as a result of acute on chronic, severe elevations of intraocular pressure (IOP) that lead to ischemic necrosis and further cavernous or cystic degeneration of the optic nerve. This forces the silicone oil to move from the vitreous into the optic disc and nerve. Continued elevation of IOP promotes extension of silicone oil through the nerve and into the perineural subarachnoid space, eventually communicating with the intraventricular cavities. Because both blood and intracranial silicone oil demonstrate similar characteristics on imaging, it can be difficult to distinguish between the 2 on CT and magnetic resonance imaging (MRI) sequences. The distinction between the 2 can help optimize the use of health care resources, and potentially prevent poor outcomes. In our case, the patient had to undergo cerebral angiogram for clarification purposes, despite having underlying CKD. To help differentiate between both, silicone oil has a spherical configuration due to its high surface tension, whereas blood will present as a fluid-fluid level. Second, silicone oil has a lower specific gravity when compared with cerebrospinal fluid (CSF; 0.97 g/ml vs 1.00) shifting it to a nondependent location, whereas hemorrhage will move toward dependent portions of the ventricles. Therefore, an easy way to distinguish between both is to repeat imaging studies having the patient change from supine to prone positions, thus forcing the displacement of the silicone oil.