Posterior-Transcallosal Approach to a Choroidal Fissure Arteriovenous Malformation: Video of Adapting a "Bridging Vein Free" Corridor to This Complex Region.

Choroidal fissure arteriovenous malformations (ChFis-AVMs) are uncommon and challenging to treat due to their deep location and pattern of supply. The choroidal fissure lies between the thalamus and fornix, from the foramen of Monroe to the inferior choroidal point. AVMs in this location receive their supply from the anterior, lateral posterior choroidal artery and medial posterior choroidal arteries and drain to the deep venous system. The anterior-transcallosal corridor to the ChFis is favored due to the ease in opening the taenia fornicis from the foramen Monroe, and it increases in length for lesions located more posteriorly. We present a case of a posterior ChFis-AVM. The patient, a previously healthy woman in her 20s, presented with a sudden severe headache. She was diagnosed with intraventricular hemorrhage. This was managed conservatively with subsequent magnetic resonance imaging and digital subtraction angiography revealing a ChFis-AVM at the body of the left lateral ventricle, between the fornix and superior layer of the tela choroidae. It received its supply from the left lateral posterior choroidal artery and medial posterior choroidal artery and drained directly into the internal cerebral vein, classified as Spetzler-Martin grade II. A posterior-transcallosal approach to the ChFis was chosen to reduce the working distance and afford a wider corridor by avoiding cortical bridging veins (Video 1). Complete resection of the AVM was achieved with no additional morbidity. Microsurgery in experienced hands offers the best chance of cure for AVMs. In this case we demonstrate how to adapt the transcallosal corridor to the choroidal fissures for safe AVM surgery in this complex location.