It is now possible to obtain information about intracranial blood flow velocity by the use of transcranial doppler. We investigated transcranial doppler flow velocities in 42 cluster headache patients, and 41 controls. Interhemispheric asymmetry was significantly greater in the cluster headache group. Within the patient groups, velocities in the middle cerebral artery and posterior cerebral artery, were significantly faster on the headache side and slower in the anterior cerebral artery.
Prophylactic medication seems to block these changes.