Vascular Malformations of the Spinal Cord

　　The vascular malformation of the spinal cord is a congenital lesion, and its understanding is based on pathological anatomy, with arterial or venous malformation as the main lesion, and in the past, it focused on the pathological physiological effects of veins. Based on magnetic resonance imaging and selective spinal angiography, combined with gross pathological findings, the vascular malformation of the spinal cord is now divided into four main types:

　　1. Type I Type I is a dural arteriovenous malformation, with the malformation forming a shunt located in the dura mater, usually involving the dural sheath of the nerve roots or the posterior lateral dura of the thoracic and lumbar spinal canal, located within the neural foramen. The arterial supply of the dural arteriovenous malformation originates from the dural branches of the segmental arteries of the spine, supplying the nerve roots and the dura. In the lower blood flow within the dura, the venous return goes through the lesion to the dura and then returns to the coronal veins of the spinal cord. These veins are located on the dorsal lateral aspect of the spinal cord, without venous valves. Therefore, an arteriovenous fistula communication is formed between the segmental arteries of the spine and the venous return veins of the spinal cord. This fistula also communicates with the coronal fistulas on the posterior and posterolateral aspects of the spinal cord.

　　2. Type II Type II is a vascular ball malformation, with an arteriovenous vascular mass in the spinal cord. These lesions are often found in the cervical spinal cord, but can also occur at any part of the thoracolumbar segment. Their characteristic is the high blood flow and sparse venous return vessels shown in angiography. There are often varices and varicose veins.

　　3. Type III Vascular malformations of the spinal cord were initially called 'immature malformations', characterized by high blood flow and extensive and complex arterial and venous anatomy. Lesions can occupy the entire spinal cord, invade the dura mater, and even extend to the vertebral bodies and paravertebral tissues.

　　4. Type IV Vascular malformations of the spinal cord are located in the epidural-extramedullary area, with one branch of the anterior spinal artery serving as the nutrient artery for the arteriovenous malformation, and then returning to the extramedullary veins of varying sizes through a fistula. The arteriovenous fistula and its reflux veins are located outside the spinal cord, and the lesion is not within the spinal cord. Such lesions are usually located at the thoracolumbar junction. Anson and Spetzler further divided type IV into subtypes: type IVa is relatively small, with the extramedullary arteriovenous fistula supplied by a single nutrient artery, usually extending from the ventral side to the conus. Type IVb has more than one nutrient artery, usually originating from the anterior spinal artery and multiple nutrient arteries 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 supply arteries connected to the fistula. The venous blood return flow of the lesion is often very large, and varicose veins are often expanded on the ventral and lateral sides of the thoracolumbar canal.

　　Types II, III, and IV spinal cord vascular malformations originally belong to intradural vascular malformations. In addition to the above four types, there are also cavernous vascular malformations.

　　5. Cavernous vascular malformation Cavernous vascular malformations can exist as a single lesion or as part of a cavernous angioma of the craniospinal axis in the form of a part of the spinal cord. These low-flow lesions are composed of stratified vessels within the spinal cord substance or vascular channels of multiple segments, which can cause intraradicular hemorrhage or compressive symptoms. Cavernous angiomas can occur throughout the central nervous system. These lesions are composed of vessels with thin walls that lack obvious elastic protein or smooth muscle. These thin-walled tubes are lined with endothelial cells and often show signs of old hemorrhage. No scattered normal spinal cord or brain substance can be seen between the vascular walls.

　　Vascular malformations of the spinal cord may be accompanied by subarachnoid hemorrhage. The main clinical manifestations occur under conditions such as emotional excitement, physical labor, coughing, forceful defecation, drinking, sexual intercourse, etc., with positive meningeal irritation signs, hemorrhagic manifestations on brain CT scans, and uniform and consistent bloody cerebrospinal fluid in lumbar puncture. The severity of symptoms depends on the location of the lesion, the amount of bleeding, and is also related to the age of onset.

　　The clinical symptoms of spinal cord vascular malformations include:

　　1. Radicular pain
　　There is radiation pain in the distribution area of the nerve root where the lesion is located, such as neck, back, lumbar, or bilateral lower limb radiation pain. Changes in body position can induce pain, which can be spontaneously relieved after rest. Pain can affect two or more nerve root distribution areas.

　　2. Progressive radicular and spinal cord dysfunction
　　Manifested as varying degrees of motor, sensory, and sphincter dysfunction in different parts: muscle weakness, intermittent claudication, sensory reduction or loss, incontinence of urine and feces, etc. The typical symptom is intermittent claudication, where the patient feels muscle weakness and pain after walking a certain distance, and the symptoms disappear after rest. The symptoms recur after walking a certain distance again. The cause is the phenomenon of stealage from malformed vessels, causing chronic ischemia of the spinal cord; when exercising, blood is redistributed, and it accumulates more in skeletal muscles, which exacerbates spinal cord ischemia and produces symptoms.

　　3. Acute hemorrhage
　　Sudden onset of severe radicular pain, paraplegia or quadriplegia, blood can flow reversibly into the cranium, causing headache, vomiting, or convulsions, and there may be loss of consciousness. When a hematoma forms, direct destruction or compression of the spinal cord can cause rapid loss of spinal cord function.

　　4. Associated with other deformities
　　It often occurs with spinal deformities, vascular nevi (moles) on the skin of the corresponding segment of the back, intracranial vascular malformations, aneurysms, liver or kidney hemangiomas.

　　The etiology of spinal cord vascular malformations is not clear, and it may be related to environmental factors, genetic factors, dietary factors, and emotional and nutritional factors during pregnancy. Therefore, this disease cannot be prevented directly. Early detection, early diagnosis, and early treatment are of great significance in preventing the disease. Regular checks should be done during pregnancy. If the child shows a tendency of developmental abnormalities, chromosomal screening should be done in time, and if confirmed, an artificial abortion should be performed in time to avoid the birth of children with the disease.

　　Rupture of malformed vessels may lead to subarachnoid hemorrhage, and blood-stained cerebrospinal fluid may be found during lumbar puncture.

　　1. Plain filmVentricular angioma of the vertebrae can be seen as a latticed porous vertebrae, vascular malformations within the spinal cord can be seen as widening of the spinal canal and pedicle distance, similar to intramedullary tumors; Cobb syndrome can be seen as destruction of the vertebral body and pedicle roots.

　　2. MyelographyThis is the most important first step in diagnosing spinal cord lesions. It not only provides non-direct imaging of the spinal cord itself but also shows the direct imaging of the peri-spinal blood vessels. Non-ionic, water-soluble contrast agents should be used during the examination, which have few side effects and can be well diffused in the subarachnoid space, fully displaying the lesions. At the same time, they can be quickly absorbed without affecting further angiography. CT scan or myelography can be added if necessary.

　　3. CT scanAfter the lesion segment is clearly identified by myelography, a CT scan is performed to have a more comprehensive understanding of the lesion. Plain scan can detect intramedullary hematoma and calcification, and intrathecal injection of contrast agent can show the arachnoid membrane. Abnormal filling defects are seen in the subdural space, and after contrast enhancement, abnormal vascular masses within and around the spinal cord can be displayed.

　　4. Magnetic Resonance Imaging:It is possible to fully understand the location of intramedullary vascular malformations, the size of the vascular masses, whether there is venous thrombosis, and use it for follow-up after surgery or angiography. In addition to cavernous hemangiomas, all types of vascular malformations in MRI images are displayed as serpentine low signal flow emptying phenomena. When there is venous congestion in the subarachnoid space or within the spinal cord, it can be displayed as spinal cord enlargement, with signals that are either strong or weak. Intramedullary cavernous hemangiomas are characterized by a more typical 'black ring' sign on the T1-weighted image, which is high signal in the middle, indicating the deposition of hemosiderin after hemorrhage, and low signal around it.

　　5. Spinal cord angiography:This method is the only method currently used to diagnose and classify spinal cord vascular malformations, and it also provides extremely valuable information for treatment.

　　Spinal cord vascular malformations are congenital lesions, and there are no special dietary requirements for patients. During pregnancy, women need a nutritious and balanced diet, appropriate exercise, to ensure the normal and healthy development of the fetus, and to prevent the occurrence of congenital diseases.

　　The main cause of spinal cord lesions in patients with this disease is the increased pressure of the coronal venous plexus and the decreased perfusion pressure within the spinal cord, so the goal of treatment is to eliminate the arteriovenous fistula connections that cause increased venous pressure, and intravascular surgery or microsurgery can achieve this goal.

　　First, type I treatment
　　1. Endovascular embolization: For patients with spinal cord dura arteriovenous malformations, endovascular treatment is mainly used to terminate the distal feeding arteries, arteriovenous communications, and the proximal part of the intradural venous reflux by means of embolization or occlusion, and it is also possible to embolize the root of the feeding arteries.
　　If it is difficult to selectively catheterize the segmental spinal cord arteries, or if the direct or collateral blood supply of the anterior spinal artery to the arteriovenous fistula supplying the dura mater through the segmental spinal cord arteries, then endovascular treatment should be contraindicated, and surgical operation should be performed at this time. 10% to 15% of spinal cord dura arteriovenous fistulas are supplied by arteries that also supply the anterior spinal artery.

　　2. Microsurgical surgery: The microsurgical treatment of spinal dura arteriovenous malformations includes coagulation and transection of intradural reflux veins, or excision of intradural nerve root sheath arteriovenous malformation lesions, while coagulating and transecting the reflux veins.
　　The patient is placed in a prone position during surgery, and it is crucial to locate the lesion level before and during the operation. Laminectomy is performed in a certain range above and below the venous-arterial malformation lesion. Examination of the dura mater and the proximal nerve root sheath, for segmental arteries that do not supply both the anterior spinal artery and the venous-arterial malformation at the same time, it is possible to excise the dura mater and the venous-arterial malformation, and then repair the dura mater. When opening the dura mater, identify the accompanying nerve root dura mater veins and coagulate them with electricity. For patients with segmental arteries that supply both the anterior spinal artery and the arteriovenous fistula, it is necessary to incise the dura mater, coagulate and cut the intradural veins in the subarachnoid space and the posterior lateral aspect of the spinal cord, and then repair the dura mater.

　　2. Type Ⅱ, Ⅲ Treatment
　　The treatment of intramedullary arteriovenous malformations often combines the methods of intravascular treatment and microsurgical surgery. When there are many arterial supplies from the posterior spinal cord arteries, intravascular treatment is the most effective method. The injection of angiography in the anterior spinal cord arteries may damage the normal spinal cord blood flow and become complex, especially when the anterior spinal cord arteries do not terminate at the vascular malformation. Temporary balloon occlusion, pentobarbital test, and somatosensory evoked potentials (SEP) help in selecting cases for intravascular treatment. Microsurgical treatment of intramedullary arteriovenous malformations is suitable for multiple vascular spheroid lesions. These lesions are often scattered and have clear arterial supply. Immature lesions tend to be more extensive in the spinal cord and involve a wider range. Distinguishing these lesions from functional spinal cord tissue is often difficult. The application of somatosensory evoked potentials and temporary ligation of feeding arteries helps in microsurgical manipulation of these lesions. Generally, lesions located on the dorsal or midline are most suitable for surgical treatment. Lesions extending from the head to the tail direction over two vertebral segments, as well as lesions closely connected with the anterior spinal cord artery, are not suitable for surgical treatment.

　　3. Type Ⅳ Treatment
　　Combining intravascular treatment and microsurgical surgery. Since type Ⅳa lesions are usually smaller feeding arteries with low blood flow, they are usually not suitable for intravascular treatment. Surgical management sometimes includes intraoperative angiography to confirm complete occlusion of the arteriovenous fistula, which is an effective treatment method for type Ⅳa, Ⅳb lesions, especially suitable for lesions on the lateral side of the thoracolumbar spinal canal. For type Ⅳc lesions, intravascular embolization is performed using floating balloons, sometimes using metallic coils or injectable embolic materials.

　　4. Treatment of Cavernous Vascular Malformations
　　Saccular vascular malformations without symptoms occurring in the spinal cord do not require special treatment. The risk of bleeding in intracranial cavernous vascular malformations is estimated to be 0.25% to 0.8% per person per year. Although there is a risk of deterioration of neurological function in patients with asymptomatic lesions, the risk seems to be low. In patients with symptoms, especially those with recurrent episodes of neurological deterioration due to bleeding, surgical treatment is effective.