• headache;
  • cervical sympathectomy;
  • carotid blood flow;
  • cranial tissue distribution;
  • microsphere technique;
  • sympathetic stimulation

Background.—A patient developed severe, continuous, unilateral headache that was “vascular” in nature, following cervical sympathectomy.

Objective.—To determine the changes in cranial blood flow in the cat following lesioning and stimulation of the cervical sympathetic nerve.

Method.—Carotid blood flow was determined by electromagnetic flowmetry and its tissue distribution by intra-arterial injection of 15-μm radioactive microspheres.

Results.—Following sympathetic lesioning, an increase in carotid blood flow was observed and reversed with stimulation. The distribution of carotid blood flow changed for the brain only, maintaining relatively constant tissue perfusion.

Conclusion.—An increase in cerebral blood flow could not have accounted for the sympathectomy-induced headache. Dilation of major cerebral arteries and cranial noncerebral vasodilation probably constitutes its mechanism.