Plasma collection will be done at the same visit as the lumbar puncture. Blood will be drawn into tubes containing either EDTA (5 x 6 ml tubes) or Lithium heparin (3 x 3 ml tubes) as anticoagulant. After centrifugation (2000g, +4°C, 10 min), plasma samples will be aliquoted into polypropylene tubes and stored at -80°C pending biochemical analyses. Further, EDTA-blood (2 x 6 ml) will also be obtained for genetic DNA analyses.