Low-flow direct carotid-cavernous fistula caused by rupture of an intracavernous carotid aneurysm.

Direct carotid-cavernous fistulas (CCFs) secondary to a ruptured intracavernous carotid aneurysm (ICCA) are usually high-flow lesions. On very rare occasions, a ruptured ICCA may present as a low-flow CCF, which poses a diagnostic and therapeutic dilemma whether the aneurysm and the observed fistula are causally related. Herein, we describe a rare case in which a ruptured ICCA resulted in a low-flow CCF. We demonstrated our approach to clarify this clinical scenario, and also propose a possible pathomechanism to explain the existence of low-flow direct CCF.