AUTHOR=Olesen Niels D. , van Lieshout Johannes J. , Fisher James P. , Seifert Thomas , Nielsen Henning B. , Secher Niels H. 

TITLE=Case report: (Pre)syncopal symptoms associated with a negative internal jugular venous pressure

JOURNAL=Frontiers in Physiology

VOLUME=5

YEAR=2014

URL=https://www.frontiersin.org/journals/physiology/articles/10.3389/fphys.2014.00317

DOI=10.3389/fphys.2014.00317

ISSN=1664-042X

ABSTRACT=<p>A siphon is suggested to support cerebral blood flow but appears not to be established because internal jugular venous (IJV) pressure is close to zero in upright humans. Thus, in eleven young healthy males, IJV pressure was 9 ± 1 mmHg (mean ± <italic>SE</italic>) when supine and fell to 3 ± 1 mmHg when seated, and middle cerebral artery mean blood velocity (MCA V<sub>mean</sub>; <italic>P</italic> &lt; 0.007) and the near-infrared spectroscopy-determined frontal lobe oxygenation (S<sub>c</sub>O<sub>2</sub>; <italic>P</italic> = 0.028) also decreased. Another subject, however, developed (pre)syncopal symptoms while seated and his IJV pressure decreased to −17 mmHg. Furthermore, his MCA V<sub>mean</sub> decreased and yet within the time of observation S<sub>c</sub>O<sub>2</sub> was not necessarily affected. These findings support the hypothesis that a negative IJV pressure that is a prerequisite for creation of a siphon provokes venous collapse inside the dura, and thereby limits rather than supports CBF.</p>