Meningitis in a young child from the medieval site of Helgeandsholmen, Stockholm, Sweden. Meningitis is an acute inflammation of the meninges of the brain. The inflammation can be caused by infection, viruses or bacteria and is considered life-threatening if not treated, due to the close proximity to the brain and spinal cord. In ancient populations this can be seen as changes on the endocranial surface of the skull, as seen above.