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.
Healthy volunteer.
Age >= 18 years.
Able to give written and oral informed consent.
Prior evaluation under NIH protocol 89N0045.
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.
Single group
Gadobutrol
Drugcontrast agent
Occurrence of intervention-emergent adverse events at the participant level assessed descriptively
Systematic recording of adverse events is essential to determine the safety of IT gadobutrol, especially given its off-label use in healthy volunteers. With the limited sample size of this Phase 1 study, safety assessment is appropriately based on a descriptive evaluation rather than formal hypothesis testing. Monitoring known procedure- and contrast-related risks (e.g., post-lumbar puncture headache, nausea, dizziness) as well as any unexpected adverse events over the study and follow-up period provides the critical foundation for ethical justification and regulatory decision-making and is a prerequisite for future feasibility and efficacy-driven studies.
Participant-level MRI detection status (yes/no) of contrast in the cerebral SAS
Technical feasibility is assessed by determining whether IT administered GBCA can be visually detected in the cerebral SAS at 24 hours under exploratory Phase 1 conditions. As this is a pilot safety study with limited prior human data, feasibility is not used as a stopping criterion. Instead, MRI visibility of contrast will inform adaptive dose escalation. If no or insufficient contrast enhancement is observed in 3 to 5 participants at the initial dose level (0.25 ml), the dose may be escalated to 0.5 ml to improve detectability. This predefined adaptation is intended to support appropriate dose selection for subsequent studies while maintaining the focus on safety.
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