Sensitive methods for the detection of soluble polySia-ESL-1, polySia-NRP2, or even polySia-SynCAM 1 in extracts from brain tissue or in cerebrospinal fluid will allow to determine if shedding of polysialylated proteins by activated microglia, invading monocyte-derived macrophages, and possibly OPCs occurs during acute or chronic neuroinflammation after TBI or other brain insults, in neurogenerative diseases, or in the immune environment of brain tumors. Here, NRP2 is linked to glycogen storage disease VI.