Dynamic Magnetic Resonance Imaging of Human Subarachnoid Space Using Intrathecal Gadolinium Contrast

Background: Cerebrospinal fluid (CSF) is the liquid that fills the space around the brain and spinal cord. Researchers do not fully understand how CSF flows and drains around the brain. They want to test a tracer (gadobutrol)-a special dye injected into the CSF-to find out if it is safe to use and can help them get clearer pictures of the CSF during magnetic resonance imaging (MRI) scans of the brain. Objective: To test gadobutrol in the CSF during MRI scans of healthy people. Eligibility: Healthy volunteers aged 18 years and older. They must be screened under NIH protocol 89N0045. Design: Participants will check into the clinic for a 3-day stay. They will have a lumbar puncture: An area on their lower back will be numbed. A thin needle will be inserted into the space around the spinal cord. A sample of CSF will be taken for research. Then a low dose of gadobutrol will be injected into the CSF. Participants will have 4 or 5 MRI scans of the brain-30 minutes, 4 hours, 8 hours (this one is optional), 24 hours, and 48 hours after receiving the gadobutrol. For the scan, they will lie on a table that slides into a cylinder. Special padding will be used to hold their head still. The MRI uses magnetic fields to create images of the inside of the body. Blood and urine samples will also be collected at each scan. Participants will return for an additional MRI 1 week after they leave the clinic. They will have 2 follow-up phone calls 4 and 12 weeks after the start of the study.

* INCLUSION CRITERIA: To be eligible to participate in this study, an individual must meet all the following criteria: * Healthy volunteer. * Age \>= 18 years. To explore age-related effects on tracer dynamics and clearance, 3 cohorts of participants will be recruited: 1) 18-30 years, 2) 30-55 years, and 3) \>55 years; with 2 males and 2 females in each age group. * Able to give written and oral informed consent. * Prior evaluation under NIH protocol 89N0045. EXCLUSION CRITERIA: An individual who meets any of the following criteria will be excluded from participation in this study: * History of chronic neurological illness, or significant concurrent medical illness. * Contraindication to 3- or 7-tesla MRI * Hypersensitivity reactions to contrast agents. * History of severe allergic reactions. * Pregnancy or breastfeeding. * Renal dysfunction or other serious comorbidities. * Platelet count \ 1.5 or prolonged PT or aPTT at baseline. * Any of the following imaging findings: Mass effect, midline shift, herniation (tonsillar, uncal, subfalcine), or Chiari malformation. * History of seizures or seizure disorder. * Anti-coagulation therapy. * Unwilling to allow coded samples to be processed offsite. * Unwilling to have coded samples and/or data saved or used in other studies.