C-C Fistula:

Laceration of the intracavernous portion of the carotid artery or one of its intracavernous branches resulting in a direct communication between the internal carotid artery and the cavernous sinus. Clinically, this produces a pulsatile exophthalamus and a marked limitation of extraocular motion in the affected eye. CRANIOCEREBRAL TRAUMA, especially basilar skull fractures (SKULL FRACTURE, BASILAR) is the most common cause of this condition, but it may also occur spontaneously or in association with diseases featuring defective connective tissue, such as EHLERS-DANLOS SYNDROME. (Adams et al., Principles of Neurology, 6th ed, p877)