A patient is suffering from proven neurosyphilis if, in addition to fulfillment of the criteria of probable neurosyphilis, a local treponeme-specific antibody reaction can be detected, measured via the detection of intrathecal production of antibodies against T. pallidum (ITpA = intrathecally produced T. pallidum antibodies) or a TPHA CSF/serum antibody index. Here, ITPA is linked to neurosyphilis.