Inflammatory and Infectious Diseases of the Nervous System

Background: \- Inflammation is how the body reacts to infection or injury. Infections or inflammation in the brain and nerves can be serious. There aren t always good tests to detect this. Researchers want to learn more about how diseases affect the brain and nerves to develop better tests and treatments. Objective: \- To learn more about how inflammation and infections hurt the brain and nervous system. Eligibility: \- People at least 2 years old with a diagnosis or suspected diagnosis of nervous system infection or inflammation. Design: * For some participants, a clinician outside of NIH will collect blood, tissue, and other samples. These will be sent to NIH and analyzed. * Other participants will have several visits to NIH. Children may not have all these tests. * Participants will have: * Medical history. * Physical and neurological exam. * Blood and urine samples collected. * Saliva collected. They will chew on a piece of sterile cotton for one minute. * Magnetic resonance imaging (MRI) scan. The scanner is a metal cylinder in a strong magnetic field. Participants will lie on a table that slides in and out of the cylinder. Participants will get a contrast agent through an intravenous (IV) catheter during the MRI. A needle will be used to guide a thin plastic tube (catheter) into an arm vein. * Lumbar puncture. Skin will be numbed and a needle will be inserted into the space between the bones in the back. Fluid will be removed. * Some participants may have optional study procedures. These may include eye tests, memory and thinking testing, tests with electrodes on the head, or skin biopsy.