Delayed middle cerebral artery occlusion following endovascular coiling of carotid terminus aneurysm

Endovascular coil embolization of intracranial aneurysms is a relatively safe and effective alternative to traditional clip ligation. While bare platinum coils have long been used with good success, newer bioactive coils have been developed since approximately 2002 in an attempt to improve occlusion rates. Although unexpected complications such as aseptic meningitis, seizures, new-onset headaches, hydrocephalus, cranial nerve palsies and delayed visual compromise have been described following the use of both bare platinum coils and bioactive coils, we have not yet seen reports of delayed large vessel occlusion. We describe an unusual case of an uncomplicated, elective endovascular coil embolization of a right internal carotid artery (ICA) terminus aneurysm using a combination of bare platinum coils and HydroCoils leading to the delayed occlusion of the proximal M1 segment of right middle cerebral artery (MCA) with no clinical sequelae.