Figure 2
From: No evidence of jugular venous valve insufficiency in patients with migraine – a controlled study
Doppler sonography of venous valve flow during closure. A shows Doppler sonography of venous flow during closure of a competent jugular venous valve by Valsalva maneuver. The arrows indicate the beginning and the end of the backward flow. After valve closure no orthograde venous flow appears because of an ongoing Valsalva maneuver over several seconds. B shows prolonged backward flow in an insufficient valve. Notice the different graduation of the scale of flow velocity revealing a higher peak velocity flow in the insufficient valve.