Pain in the back or buttocks of the thoracolumbar segment may be the main symptom of spinal vascular malformation, which is less common and most commonly presents as a subarachnoid hemorrhage or spinal cord hemorrhage. Spinal cord vascular malformations can occur in any segment of the spinal cord, but most commonly in the cervical segment and conus. What causes pain in the back or buttocks of the thoracolumbar segment? 1.Type I Type I is dural arteriovenous malformation. The arteriovenous malformation forms traffic located in the dura, usually involving the nerve root sleeve or the posterior lateral dura of the thoracolumbar segment, located in the neural foramen. The arterial supply to the dural arteriovenous malformation originates from the dural branches of the segmental arteries of the spine, which supply the nerve roots and dura mater. The lower blood flow in the dura through the lesion and its veins return to the dura and then to the coronary veins of the spinal cord. This group of veins is located dorsolateral to the spinal cord and has no venous valves. As a result, arteriovenous fistula traffic is formed between the segmental arteries of the spinal column and the spinal reflux veins. This fistula also communicates with the posterior and postero-lateral coronary fistulae of the spinal cord. This fistula also communicates with the posterior and postero-lateral coronary venous plexus of the spinal cord. Blood from the coronary plexus flows upward to the foramen magnum. 15% of the segmental arteries in the plane of the arteriovenous fistula supply the anterior or posterior spinal cord arteries. Anson and Spetzler further divided type I into subtypes Ia for a single trophoblastic artery and Ib for multiple trophoblastic arteries, usually in one or two segments adjacent to each other, depending on the number of trophoblastic arteries. The mean static pressure of a dural arteriovenous fistula is approximately 74% of the systemic arterial pressure. Hemodynamic evidence shows that the pathophysiology of type I dural arteriovenous malformation neurological dysfunction is mainly due to the elevation of venous pressure, which manifests as coronary venous congestion and dilation, followed by compression of the spinal cord, but such spinal cord neurological dysfunction is reversible. These lesions are often seen in the cervical spinal cord, but can also occur anywhere in the thoracolumbar segment. They are characterized by high blood flow and sparse venous reflux vessels on angiography. Venous aneurysms and varicose veins are often present. Type III spinal cord vascular malformation is initially called “immature malformation” characterized by high blood flow and extensive and complex arterial and venous anatomy. The lesion can occupy the entire spinal cord, invade the dura, and even extend to the vertebral body and paravertebral tissue. Type IV spinal vascular malformation is located in the intradural-epidural region, and a branch of the anterior spinal artery is the trophoblastic artery of the arteriovenous malformation, which then returns to the extramedullary veins of different sizes via fistulas. The arteriovenous fistula and its returning vein are located outside the spinal cord and the lesion is not located in the spinal cord. Anson and Spetzler further divided type IV into subtypes: type IVa is a relatively small, extramedullary arteriovenous fistula supplied by a single trophoid artery, usually located ventrally and extending to the conus. Type IVb has more than one trophoblastic artery, usually from the anterior spinal artery, and multiple trophoblastic arteries originating from the posterior spinal artery. The blood flow through these lesions is greater than that through type IVa fistulas. Type IVc is characterized by multiple supplying arteries connected to the fistula. Venous blood flow back to the lesion is often high, and dilated varices are often present ventral and lateral to the thoracolumbar spinal canal. Types II, III, and IV spinal vascular malformations are originally intradural vascular malformations. In addition to the above 4 types, there are also cavernous vascular malformations. 5, cavernous vascular malformations Spongiform vascular malformations can occur in the spinal cord in the form of a single lesion or as part of a craniospinal cavernous angioma. These low-flow lesions consist of stratified vessels or multisegmental vascular channels within the spinal cord parenchyma, and can occur with intra-radicular hemorrhage or compression symptoms. Spongiform hemangiomas can occur throughout the central nervous system. These lesions consist of a number of thin, vascular wall layers with no apparent elastin or smooth muscle. These thin-walled vessels are lined with endothelial cells and often show signs of old hemorrhage. Scattered distribution of normal spinal cord or brain parenchyma is not seen between the vessel walls.