Bilateral ethmoidal dural arteriovenous fistula: unexpected surgical diagnosis.

Dural arteriovenous fistulae (DAVFs) are infrequent lesions, the most common locations of which are the cavernous, sigmoid and transverse sinuses. The cribiform plate is one of the less frequent sites for DAVFs, where they entail a high hemorrhage risk. Feeding arteries for ethmoidal DAVFs can be uni- or bilateral. However, the draining fistulous system has classically been described as unilateral. The authors report the second case in literature of bilateral ethmoidal DAVF, which is defined as that with bilateral draining veins. The present case was diagnosed only after surgical exploration of both cribiform plates. No preoperative radiological test could detect the presence of a bilateral venous draining system from the ethmoidal DAVF. Possible reasons for that lack of presurgical diagnosis are discussed. Bilateral surgical exploration of the anterior cranial fossa is recommended when dealing with ethmoidal DAVFs, even when they seem to be unilateral on preoperative studies.