[1] Univ Witten Herdecke, Fac Med, IFOM, Inst Res Operat Med, D-51109 Cologne, Germany
[2] GSF, Natl Res Ctr Environm & Hlth, Inst Dev Genet, Munich, Germany
[3] Univ Cologne, Fac Med, Clin Neurosurg, D-5000 Cologne 41, Germany
[4] Univ Witten Herdecke, Hosp Merheim, Fac Med, Dept Traumat & Orthoped Surg, D-51109 Cologne, Germany
[5] Univ Cologne, Fac Med, Dept Neurophysiol, D-5000 Cologne 41, Germany