Article History
First Online: 30 April 2018
Compliance with ethical guidelines
:
: G. Keyßer, S. Zierz, and M. Kornhuber declare that they have no competing interests.
: All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. Informed consent was obtained from all individual participants included in the study.