INCLUSION CRITERIA:
In order to be eligible to participate in this study, an individual must meet all of the following criteria:
Multiple Sclerosis Inclusion Criteria
-Enrolled in the NINDS Natural History Study for MS (protocol 89-N-0045)
-Able to understand, and willing to sign, a written, informed consent document.
-Willing to comply with all study procedures and available for the duration of the study.
-Male or female, aged >=18.
-Diagnosis of MS according to the 2017 revision of the McDonald diagnostic criteria48 (in the presence or absence of a clinical relapse).
PML Inclusion Criteria
-Enrolled in the NINDS Natural History Study for PML (protocol 13-N-0017)
-Able to understand and willing to sign a written, informed consent document
-Willing to comply with all study procedures and available for the duration of the study.
-Male or female, aged >=18.
-Diagnosis of definite PML according to 2013 AAN Consensus Criteria49 or PML-IRIS based on clinical, radiological and laboratory evidence.
Patients with Known or Suspected Neuroinflammatory Diseases and Evidence of Open BBB Inclusion Criteria
-Clinical evaluation suggesting an inflammatory disorder of the central nervous system other than MS or PML. Other confirmed neuroinflammatory disorders may include -MOGAD, NMOSD, Behcet's syndrome, and neurosarcoidosis. Unconfirmed, though
suspected cases of neuroinflammation may also be included.
-Recent brain MRI (within 1 month) with gadolinium enhancement indicating open BBB.
-Able to understand and willing to sign a written, informed consent document.
-Willing to comply with all study procedures and available for the duration of the study.
-Male or female, aged >=18.
EXCLUSION CRITERIA:
An individual who meets any of the following criteria will be excluded from participation in this study:
-Pregnant or lactating.
-Contraindications for MRI gadolinium contrast administration or 3T MRI.
-History of, or current diagnosis with, concomitant medical or clinical conditions that would adversely affect participation in this study.
-Weighs > 350 lb. (158 kg; weight limit for the scanner table) or is unable to fit within the MRI or PET imaging gantry.
-Severe claustrophobia unresponsive to oral anxiolytics.
-Has an alkaline phosphatase level greater than 2x ULN (unless known to have non-liver related disorder) OR AST greater than 1.5 x ULN OR ALT greater than 1.5 x ULN.
-Has a total bilirubin >1.5X ULN, unless known to have elevated bilirubin due to nonliver related disorder or Gilbert s.
-Creatinine clearance < 60 mL/min as estimated by the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI)
-For females of reproductive potential: inability to use highly effective contraception for at least one month prior to screening and during study participation.