REMODELING AND COMPARTMENTALIZATION OF THE NIDUS AS A SOLUTION FOR SAFE RESECTION OF RUPTURED UNEMBOLISED LARGE AND GIANT ARTERIOVENOUS MALFORMATIONS

Introduction Arteriovenous malformations (AVMs) consist of fistulous connections of arteries and veins without intervening capillaries, organized as a mass with definable sides. AVMs are composed of enlarged feeding arteries, a nidus of dysmorphic vessels in relationship with the brain parenchyma, through which arteriovenous shunting occurs and draining veins. In a series of corticalised and deep avm’s the senior author conceptualised the nidus as composed of two or more compartments that can be separated completely after partial disconnection from corresponding feeding arteries and unessential drainage veins. This surgical strategy allowed a wider surgical corridor to the deeper AVM compartments, a faster resection and reduced blood loss. Material and Methods In this study we review 4 large and one giant AVM cases removed surgically using the technique of nidus compartmentalization. Clinical and imaging data included complete surgical videos, gender, age, clinical presentation, Spetzler-Martin and Lawton-Young grade, nidus size, modified Rankin Score (mRS) were collected. Surgical Nuances The surgical strategy was adapted to the location of the main feeders. when the main feeders were deep we preferred opening a narrow deep surgical corridor to interrupt them first and then enlarging it circumferentially from depth to surface. In this scenario, the main drainage vein has a trajectory that is not perpendicular to the nidus, folding many times in close contact with one or more faces of the nidus or even inside the nidus. In this case, the classical dissecting strategy by opening surgical corridors circumferentially around the AVM, can be hazardous as the main drainage vein can be injured, resulting in heavy haemorrhage from the remaining nidus which is attached to the vein. When the main feeders came from MCA branches a superficial to deep dissection of the nidus was followed. In order to facilitate the resection, after a partial dissection of the nidus was performed, this part of it, completely freed from feeders and drainage veins was separated from the rest of the AVM with a large clip. After coagulation and resection of the nidus compartment above the clip, the circumferential interruption of deep feeders continued beyond the clip, securing another compartment of the AVM. In only one case this manoeuvrer was repeated more than 3 times. In 3 cases the division of the nidus in two compartments was enough. In three of the cases, we encountered blee