The extradural cavernous space lies in relation to the body of the sphenoid and is in direct communication with the orbit through the sphenoidal fissure. Its importance resides in the fact that it is traversed by various elements: internal carotid, and motor and sensory orbit nerves, but also the fundamental venous confluent of the middle stage of the base of the cranium represented by the cavernous sinus. Clinical symptoms of lesions in this region are determined by the respective positions and anatomical relationships of these different structures. Diagnosis can be established by computed tomography, carotid angiography, and orbital phlebography examinations. Whereas cavernous sinus thrombophlebitis is now very rarely observed, "intrinsic" pathological processes detected involve mainly intracavernous carotid aneurysms and carotidocavernous fistulae. The identification of the internal carotid intracavernous collaterals, and the increased knowledge of hemodynamic modifications resulting from carotidocavernous fistulae has led to the development of more appropriate endovascular surgical techniques. These include both elective obstruction of the fistula and the suppression of its various sources of supply. "Extrinsic" lesions of various origins, represented by different tumors of the base of the cranium, and tumors of the nasal and retronasal spaces, particularly cancer of the cavum and metastases, make up the greater part of cavernous syndromes.