In particular, the purpose of the present study was (i) to examine the temporal profile of S100B release into CSF and blood in a large cohort of patients following TBI and subarachnoid hemorrhage (SAH) longitudinally, (ii) to calculate the ratio of S100B in the CSF/serum in order to estimate the passage from CSF to blood, and (iii) to correlate the respective S100B levels with the neurological function and recovery as well as with specific events known to interfere with the BBB integrity. This evidence concerns the gene S100B and subarachnoid hemorrhage.