Abstract: The invention is directed to a method of assessing blood brain barrier permeability in an individual comprising selectively or specifically detecting a level of S 100BB homodimer in a sample of the individual, and comparing the level of S 100BB homodimer in the sample to a level of S 100B a control. The invention is also directed to methods of determining the effectiveness of a treatment for a neurological disorder wherein blood-brain barrier permeability is present in an individual in need thereof comprising detecting a level of S100B in a sample of the individual undergoing the treatment, and comparing the level of S 100B in the sample to the level of S100B in a sample from the individual obtained prior to treatment.

Abstract: The present invention relates generally to a peripheral marker or markers of blood barrier integrity and methods of using same in the diagnosis, prognosis, and treatment of a variety of diseases. The peripheral marker(s) of the present invention are particularly useful in the differential diagnosis of diseased states. The preferred embodiments of the present invention relate to methods, compositions, kits, and assays useful in determining the integrity or permeability of either a blood CSF barrier or a blood brain barrier. The various embodiments of the present invention can be used to identify subjects at risk for developing a disease associated with increased permeability of the blood brain barrier, as well as to provide insight on the ability of an agent or agents to pass through the blood brain barrier.