Karacay Ozkalayci S, et al. - Using transcranial Doppler ultrasound, researchers evaluated cerebral blood flow velocities in anterior and posterior circulation arteries, during an attack-free episode in migraine patients, with and without aura, as well as in chronic tension-type headache patients who were not receiving prophylactic medication. They noted a significant increase in basilar artery cerebral blood flow velocities relative to controls in patients with a tension-type headache. These increased basilar artery blood flow velocities in patients with chronic tension-type headache could be due to constriction of conductance or the dilatation of the resistance vessels.