Orbital Vascular Inflammation in Ischemic Optic Neuropathy and Giant Cell Arteritis

Giant cell arteritis (GCA) is an inflammation of the blood vessels. A dangerous complication is sudden vision loss due to insufficient blood supply to the optic nerve. However, it is often difficult to distinguish acute vision loss due to GCA from a similar condition of insufficient blood supply to the optic nerve, called NAION. Quick treatment with anti-inflammatory medication is needed in case of GCA to prevent vision loss on the eye and other serious complications. Patients with NAION have no benefit of the medication, but can have serious side effects, why it is very important to differentiate between these conditions. In this project, the investigators will use FDG PET/MRI with Black Blood (BB) sequences and OCT-imaging to study patients with GCA and/or ischemic optic nerve disease. The investigators will look for signs of inflammation in and around the small vessels of the orbit using PET/MRI and study subtle retinal changes using OCT images. The investigators want to answer the following research questions: Do patients with ischemic optic nerve disease and GCA show signs of inflammation in the orbital vessel wall on PET/MRI-scans, that are not present in patients with NAION? Do GCA patients without vision loss, but with signs of orbital vessel wall inflammation on PET/MRI-scans, have a higher risk of later vision loss than GCA patients without? Can subtle changes in the retina, detectable through OCT, help distinguish between GCA-related vision loss and NAION? This will, to our knowledge, be the first study to systematically use FDG PET/MRI BB-scans to illuminate vascular changes in the orbit of patients with GCA and/or ischemic optic nerve disease. The results may improve diagnosis and treatment of GCA and NAION in the future. The investigators hope that this will help prevent blindness and other serious complications in patients with GCA, while also avoiding unnecessary treatments for patients with NAION.