Pneumocephalus by Valsalva's maneuver.

@article{Schrijver2003PneumocephalusBV,
  title={Pneumocephalus by Valsalva's maneuver.},
  author={Hans M Schrijver and Henk W. Berendse},
  journal={Neurology},
  year={2003},
  volume={60 2},
  pages={345-6}
}