MR, Histologic And EM Imaging Of Intravenous Ferumoxytol In Central Nervous System (CNS) Inflammation

Inclusion Criteria: * Subjects must have a clinical, radiological or established histological diagnosis of dural or central nervous system (CNS) parenchymal based inflammatory, vascular or demyelinating lesions, radiological suspected diagnosis of vascular CNS lesions such as ischemic stroke, TIA with suspected carotid embolic origin, or vasculopathy involving the carotids (including diagnosed carotid stenosis \>50%), the aorta, the arteries of the extremities, or diagnosed thrombosis of the intraabdominal, pelvic or extremity veins, or clinical or radiological diagnosis of enlarged cervical lymph nodes in which inflammatory processes (reactive lymph nodes) is part of the differentials. * Subjects must be 18 years or older * Subjects will be followed for at least 1 month after the infusion of ferumoxytol. * All subjects or their authorized representative must sign a written informed consent and give HIPAA authorization in accordance with institutional guidelines. * Female subjects of child-bearing potential must be postmenopausal, surgically sterile, or using a reliable form of contraception for at least a month. These criteria can be waved at the discretion of the investigator if the one-month wait required is not in the best interest of the patient. * Karnofsky must be 30% or greater Exclusion Criteria: * Subjects with clinically significant signs of uncal herniation * Subjects who have a contraindication for MRI: metal in their bodies (a cardiac pacemaker or other incompatible device), are severely agitated, or have an allergy to Gd contrast material. * Subjects with known allergic or hypersensitivity reactions to parenteral iron, parenteral dextran, parenteral iron-dextran, or parenteral iron-polysaccharide preparations * Subjects with known hepatic insufficiency or cirrhosis * Subjects with known or suspected iron overload * HIV-positive subjects on combination anti-retroviral therapy are ineligible because of the potential for pharmacokinetic interactions with ferumoxytol * Pregnant or lactating women are excluded from this study because of possible risk to the fetus or infant.