Vascular malformation of spinal cord is a congenital lesion. The understanding of it is based on pathological anatomy, with arterial or venous malformation as the main lesion. In the past, the pathophysiological influence of vein was emphasized. According to magnetic resonance imaging and selective spinal angiography, combined with gross pathological findings. Vascular malformation of spinal cord can be divided into four main types (Table 1):

(2) Pathogenesis

1.Ⅰ Type Ⅰ is dural arteriovenous malformation. The traffic caused by arteriovenous malformation is located in the dura mater, which usually involves the nerve root sheath or the posterior lateral dura mater of thoracolumbar spinal canal and is located in the nerve foramen. The arteries of dural arteriovenous malformation are supplied by the dural branches of spinal segmental arteries, supplying nerve roots and dura mater. The lower blood flow in the dura mater passes through the lesion, and its veins return to the dura mater, and then to the coronary vein of the spinal cord. This group of veins is located on the dorsolateral side of the spinal cord, and there is no venous valve. Therefore, arteriovenous fistula communication is formed between segmental arteries of the spine and spinal reflux veins. The fistula also communicates with the posterior part of the spinal cord and the posterolateral coronary venous fistula. The fistula also communicates with the posterior part of the spinal cord and the posterolateral coronary venous plexus. The blood flow of coronary venous plexus flows upward to the foramen magnum. Arteriovenous fistula plane 1.5% segmental artery supplies anterior spinal artery or posterior spinal artery. There are usually only/kloc-0 nutrient arteries in the lesion, but there are also more than 2 nutrient arteries. According to the number of nutrient arteries, Anson and Spetzler further divided Type I into subtypes 1A as a single nutrient artery, and 1B as multiple nutrient arteries, usually in 1 or two adjacent segments. The average static pressure of dural arteriovenous fistula is about 74% of systemic arterial pressure. Hemodynamic evidence shows that the pathophysiology of neurological dysfunction of type I dural arteriovenous malformation is mainly the increase of venous pressure, which is manifested by congestion and dilatation of coronary vein, and then compression of spinal cord, but this neurological dysfunction of spinal cord is reversible damage.

2. Type Ⅱ Type Ⅱ is a vascular globular malformation with arteriovenous blood vessels in medulla. These lesions usually occur in the cervical spinal cord, but they can also occur in any part of the thoracolumbar segment. In angiography, it is characterized by high blood flow and sparse venous return vessels. There are often venous tumors and varicose veins.

3. Type ⅲ spinal vascular malformation was originally called "immature malformation", which is characterized by high blood flow and extensive and complicated arteriovenous anatomy. Lesions can occupy the whole spinal cord, invade the dura mater, and even extend to vertebral bodies and paravertebral tissues.

4. Type ⅳ spinal vascular malformation is located in epidural-extraspinal region. A branch of the anterior spinal artery is the nutrient artery of arteriovenous malformation, and then it flows back to extramedullary veins of different sizes through fistula. Arteriovenous fistula and its reflux vein are located outside the spinal cord, but the lesion is not in the spinal cord. This lesion is usually located in the thoracolumbar segment. Anson and Spetzler further divided type Ⅳ into subtypes: type Ⅳ A is relatively small, and extramedullary arteriovenous fistula is supplied by a single nutrient artery, usually located on the ventral side and extending to the cone. Type ⅳ b has more than one nutrient artery, usually from the anterior spinal artery, and several nutrient arteries come from the posterior spinal artery. The blood flow through these lesions is greater than that through type ⅳ a fistula. Type ⅳc is characterized by multiple blood supply arteries connected with fistula. The venous return flow of pathological changes is often very large, and there are often dilated varicose veins on the ventral and ventral sides of thoracolumbar spinal canal.

Type Ⅱ, Ⅲ and Ⅳ spinal vascular malformations are subdural vascular malformations. In addition to the above four kinds, there are cavernous vascular malformations.

5. Cavernous vascular malformation Cavernous vascular malformation can occur in the spinal cord, showing as a single lesion of the cranial spinal cord or part of cavernous hemangioma. These low blood flow lesions are composed of layered blood vessels or multi-segmental blood vessels in the spinal cord parenchyma, which can cause root canal bleeding or compression symptoms. Cavernous hemangioma can occur in the whole central nervous system. These lesions are composed of some fine blood vessels without obvious elastin or smooth muscle wall. These thin-walled tubes are lined with endothelial cells and often show old bleeding. No scattered normal spinal cord or brain parenchyma was found between the blood vessel walls.