Histopathology of the olfactory pathway due to ischemia.

Various agents, such as trauma, viral infections and neoplasms cause olfactory dysfunction. However, little is understood concerning the role of ischemia. An experimental model of brain ischemia was developed in the Mongolian gerbil, and the olfactory pathway was studied. This animal was chosen because of its incomplete circle of Willis, since poor patency of the circle of Willis is not an uncommon finding in the aging human. Ischemia was induced by unilateral ligation of one common carotid artery or temporary occlusion of both common carotid arteries. Under both circumstances, ischemic changes occurred in the lateral olfactory tract, the olfactory ventricle, and the olfactory tubercle. Damage is more severe with bilateral temporary occlusion than unilateral ligation. The olfactory bulbs and neuroepithelium, however, are resistant to ischemia.