Ans is 'c' i.e. Discontinuation of aeria radicularis magna The Aeria Radicularis Magna (aery of Adamkiewicz) is the main source of blood supply to the anterior spinal aery in the thoracolumbar segment of the spinal cord. It arises from either one of the lower posterior intercostal aeries (T9-11), or of the subcostal aery (T12), or less frequently of the upper lumbar aeries (L1 and L2). Its occlusion or interruption is one of the major reasons for spinal cord ischemia (leading to paraparesis/paraplegia) during surgery for thoracoabdominal aneurysm. "Clamping the descending thoracic aoa causes ischemia of the spinal cord and abdominal viscera. Clinically significant manifestations of hepatic, pancreatic, and bowel ischemia are relatively uncommon. However, both acute renal failure and spinal cord injury resulting in paraplegia or paraparesis remain major causes of morbidity and moality after these operations."- Schwaz 9/e p678 "Surgery to repair thoracic and thoracoabdominal aoic aneurysms is the most common cause of spinal cord infarction. Rates of spinal cord ischemia following thoracic aoic surgery have been repoed to be as high as 29 percent, but are more usually repoed as 10 to 11 percent. Both open surgery and endovascular repair are associated with spinal cord ischemia..... Many factors may play a role in this complication. These include systemic hypotension, before, during, or after the procedure; aoic cross clamping causing decreased aerial perfusion and increased spinal canal pressure; and occlusion of impoant feeding aeries such as the aery of Adamkiewicz or other intercostal aeries either by ligation, resection, or embolization." - Spinal cord infarction: Vascular anatomy and etiologies Authors Michael Mullen, MD at uptodate.com "Kieffer et al. 20 performed preoperative spinal cord aeriography in patients with thoracic and thoracoabdominal aneurysms, and identified the aeria radicularis magna (ARM) in 85%. They repoed that the risk of paraplegia was 5% if the ARM was identified preoperatively and reimplanted, whereas it was 50% if the ARM was not reattached." - Spinal Cord Protection During Thoracoabdominal Aneurysm Repair Koichi Tabayashi at uptodate.com "Occlusion of the aeria radicularis magna can cause spinal-cord ischemia with subsequent paraplegia." - Ischemic transverse myelopathy after endovascular repair of a thoracic aoic aneurysm. Reicha M, Balm R, J Endovasc Ther. 2001 Jun:8(3):321-7.