Spontaneous thrombosis of a spinal conus perimedullary arteriovenous fistula. Case report.

A 49-year-old male presented with a rare case of acute lower extremity paresis caused by spontaneous thrombosis of a spinal conus perimedullary arteriovenous fistula (AVF) after a subacute myelopathic course. Magnetic resonance imaging obtained after deterioration showed that the flow voids around the conus medullaris had changed from hypointense to hyperintense lesions. Surgery with thoracic laminoplasty was performed to determine the nature of the lesion because angiography was negative. During surgery, thrombosed abnormal vessels were observed, consistent with thrombosis of a spinal conus perimedullary AVF. Histological specimens of the thrombosed vessels exhibited vascular wall injury such as intimal alteration, wall dissection, and mural thrombus. Hemorrhage and infection were excluded. Vascular wall injury of draining veins and varices were probably one of the causes of thrombosis in the present case. Spinal arteriovenous malformation generally causes progressive venous congestive myelopathy, but the congestive myelopathy may rarely rapidly deteriorate with spontaneous thrombosis, known as Foix and Alajouanine syndrome.