Acute aortic thrombosis is a very rare vascular emergency with high mortality and morbidity rates. It presents clinically as acute bilateral ischemia of the lower limbs. Its association with flaccid paraplegia remains a very rare event, which should prompt examination of the pulses for rapid diagnosis and management. There are many causes, including cardiac rhythm disorders. Acute embolic thrombosis of the aorta, secondary to a cardiac rhythm disorder in Basedow's disease, makes this event even rarer. We report the case of a 73-year-old woman with Basedow's disease, who presented with acute thrombosis of the subrenal aorta, revealed by flaccid paraplegia. The patient underwent aortic thrombectomy within 4hours, by surgical approach of both common femoral arteries. The postoperative course was marked by persistent motor monoplegia of the right lower limb despite rapid revascularization and cruralgia of the left lower limb. The patient recovered after physiotherapy sessions.