后颅窝静脉、脊髓血管

VENOUS DRAINAGE OF THE POSTERIOR FOSSA,长沙泰和医院神经外科 何承彪,The venous drainage of the posterior fossa can be divided into 3 groups according to the location and direction of drainage: 1.superior group (Galens vein group) 2.anterior group (petrosal group) 3.posterior goup (tentorial group),VENOUS DRAINAGE OF THE POSTERIOR FOSSA,1.SUPERIOR GROUP,It consists of veins that drain to the vein of Galen, including: 1.The precentral cerebellar vein 2.The superior vermian vein 3.The anterior pontomesencephalic vein 4.The lateral and posterior mesencephalic veins.,1.1 Precentral cerebellar vein,It is one of the most important landmark in the posterior fossa, which divides the superior part of the posterior fossa into the anterior and posterior half. The precentral cerebellar vein lies in the fissure between the lingula and central lobe of the cerebellar vermis. It is formed by the convergence of the brachial veins.,1.2 Superior vermian vein,It outlines the superior part of the vermis in lateral projection. It is formed by the convergence of the veins draining the culmen of the vermis. It goes superiorly from the culmen of the vermis and ends in the Galens vein or directly drains into the precentral cerebellar vein. Above the vermis is the triangle formed by the Galens vein, superior vermian vein and the straight sinus, where locates the supracerebellar cistern.,1.3 Posterior mesencephalic vein,It may be single or multiple, after arising from the interpeduncular fossa, it goes along the lateral aspect of the mesencephalon, then goes posteriorly, superiorly and medially around the midbrain to enter the vein of Galen or the posterior part of the internal cerebral vein. Its size varies inversely with the basal vein of Rosenthal. It may connect with the petrosal vein via the lateral mesencephalic vein.,1.4 Anterior pontomesencephalic vein,It collects several small veins and runs posteriorly to enter the interpeduncular fossa, then descends along the anterior surface of the pons in the midline. It usually drains into the basal vein of Rosenthal or the posterior mesencephalic vein. In lateral projections, it outlines the interpeduncular cistern and the superior pontine cistern.,1.5 Lateral mesencephalic vein,It is relatively constant and runs in the lateral aspect of the mesencephalon between the cerebral peduncle and the tegmentum. It drains to the basal vein of Rosenthal or posterior mesencephalic vein, and may also communicate with the petrosal vein.,1.6 Quadrigeminal vein,It drains the blood from the quadrigeminal bodies into the vein of Galen.,2. ANTERIOR GROUP,It drains the blood from the anterior surface of the pons, the superior and inferior part of the cerebellum, cerebellomedullary fissure and the lateral recesses of the fourth ventricle to the petrosal vein. It is located in the cerebellopontine angle and can be displaced by surrounding space occupying lesions, which is seen in A-P projection. It is a significant landmark in A-P view.,3. POSTERIOR GROUP,It drains the blood from the inferior cerebellar vermins and the medial aspect of the cerebellar hemisphere to the straight sinus, transverse sinuses and the torcular Herophili. The inferior vermian vein is the most important vein within this group which drains blood from the inferior vermis to the straight sinus or the proximal end of the transverse sinus. In lateral view, it is at about 1cm from the inner table of the occipital bone.,POSTERIOR GROUP,The posterior group includes the superior and inferior hemispheric vein, which drain the blood from the superior and inferior medial surface of the cerebellar hemispheres separately into the straight and transverse sinuses.,THE ARTERIAL AND VENOUS ANATOMY OF THE SPINAL CORD,Anterior spinal artery,It arises from the terminal end of the vertebral artery, and runs for about 2cm antero-inferiorly and medially to join with the contralateral anterior spinal artery, then it descends along the ventromedian fissure.,Posterior spinal artery,About 73% of the posterior spinal arteries arise from the posterior inferior cerebellar artery, a minority of them arises from the vertebral artery at the level of the medulla. It descends on the lateral side of the posteror aspect of the medulla and the spinal cord. The artery is rarely seen in vertebral artery angiograms.,Along its course, the branches from the vertebral artery, ascending cervical artery, intercostal arteries, lumbar arteries, middle sacral artery and the internal iliac artery join in different segments to form the anterior or posterior longitudinal spinal axis.,SPINAL ARTERIES,Spinal arteries are divided into 3 main groups:The first goup: It consists of the vertebral artery, ascending cervical artery, deep cervical artery and the first intercostal artery ,which all arise from the subclavian artery. The second group: It is from the intercostal and lumbar arteries of aorta The third group: from the iliolumbar artery, middle sacral artery and lateral sacral artery of the internal iliac artery.,1. The first group,It consists of the vertebral artery, ascending cervical artery, deep cervical artery and the first intercostal artery which all arise from the subclavian artery. The main branches from the subclavian artery from medial to lateral are: vertebral artery, internal thoracic artery, thyrocervical trunk, costocervical trunk, all except the internal thoracic artery supply the spinal cord and vertebrae.,1.1 The thyro-cervical trunk,It is a short segment, which divides into several branches immediately after arising from the medial margin of the anterior scalenus, which include:1). Inferior thyroid artery: It runs supero-medially to supply the inferior pole of the lateral lobe of the thyroid and the superior part of the oesophagus and pharynx.2). Suprascapular artery: It supplies the supraspinatus and the infraspinatus and the scapula.3). Ascending cervical artery: It may arise together with the inferior thyroid artery, it runs superiorly to supply the cervical muscles and mostly involves in the blood supply of the spinal cord and dura.,1.2 Costocervical trunk,It is also short and has important branches including the deep cervical artery and the first intercostal artery, both of which supply the cervical spinal cord.The vertebral artery, thyro-cervical trunk and the costocervical trunk should not be neglected in spinal angiography.,2. The second group,It is from the intercostal and lumbar arteries of aorta.,Intercostal Artery,The aorta usually gives 7-11 pairs of intercostal arteries, the left side ones usually arise from the midline of the posterior wall, while the right ones usually from the posterolateral wall. The origins of T2-4 intercostal arteries are at the same level of T5 vertebral body, while origins of the T5-11 intercostal arteries are at 1 vertebral level below the corresponding artery respectively. The subcostal artery is usually at the level between T12 and L1 vertebral bodies.The distance between the origins of the intercostal arteries is about 13.5-22.5mm and increases down the vertebral column.,Lumbar Arteriy,There are ususlly 4 pairs of lumbar arteries. The left ones arise from the midline of the posterior wall of the aorta, while the right ones usually from the posterolateral wall. There is about the distance of one vertebral body between two adjacent lumbar artery.,3. The third group,The third group: from the iliolumbar artery, middle sacral artery and lateral sacral artery of the internal iliac artery.,4. Radicualar Artery,In embryonic stage, the above arterial groups give 31 pairs of radicular artery to enter the spinal canal through the intervertebral foramina along the nerve roots. They are divided into the anterior and posterior radicualar artery (Lazorthes artery).,Radicualar Artery,Radicualar arteries distribute to 3 areas: 1. To supply the nerve roots and the spinal dura 2. To supply the pial and the peripheral zone of the spinal cord 3. To supply the intramedullary part of the spinal cord.,The radicular artery involving in contribution to the third area is called the radiculomedullary artery, in adults, most of them regress, and left behind 6-8 anterior radiculomedullary arteries and 10-23 posterior radiculomedullary arteries. Because the origin of spinal arteries is variable, spinal arteriography shoud include all of the three groups mentioned above.,4.1 Radiculomedullary Artery,Radiculomedullary arteries,They are divided into anterior and posterior radiculomedullary arteries, the anterior one are larger in size but smaller in number. The largest anterior radiculomedullary artery is the Adamkiewicz artery.,The radiculomedullary artery runs anterior to the dural sheath into the intervertebral foramen . It penetrates the dura, and ascends anterior to the dentate ligament, then turns acutely downwards, at the same time it gives an ascending branch, in a hairping manner. The anterior branch runs on the ventral median fissure while the posterior ones along both sides of the posteriolateral sulcus medial to the posterior nerve roots. The ascending and descending branches are called the spinal arteries.,5. Spinal Arteries,Spinal Arteries,5.1 Anterior spinal arteries,The first anterior spinal artery is formed by the branches from bilateral vertebral arteries before their anastomosis to become the basilar artery. It starts as a single trunk from C2-3 level and descends along the ventral median fissure , to anastomose with ascending branches of segmental spinal arteries from radiculomedullary arteries, longitudinally along the whole length of the spinal cord to the conus medullaris to form the anterior longitudinal spinal axis.,In angiogram, it forms the characteristic hairpin vessels, there may be increase in the angle between the radiculomedullary artery and the anterior spinal artery. The descending branches are usually larger than the ascending branches, they both situated in the midline of the spinal canal, and appear linearly except slightly winding at the cervical and lumbar enlargement. Lateral view shows the anterior spinal artery very close to the posterior margin of the vertebral bodies, with a gap less than 2mm. The anterior longitudinal spinal axis is narrowest or even interrupted at the mid-thorax level.,4.2 Posterior Spinal Arteries,The bilateral posterior spinal arteries arise from the left and right vertebral arteries, which descend bilaterally along the posteriolateral sulcus of the spinal cord. Althought there are anastomoses between the ascending and descending branches of the posterior spinal arteries, they rarely form 2 complete posterior longitudinal spinal axis only connects in network fashion.,In angiogram, it also forms hairpin vessels. There is decrease in angles between the radiculomedullary arteries and the posterior spina arteries compared with those of the anterior spinal arteries, and sometimes they are packed together. They run on both sides of the spinal canal in winding form, with a diameter less than that of the anterior spinal arteries . In lateral projections, the posterior spinal arteries should be at 10-13 mm from the posterior margin of the verbetral bodies.,The anterior and posterior longitudinal spinal axis anastomose at 1.5 cm below the conus medullaris to form the cruciate anastomotic arch. There are coronal anastomoses between the longitudinal axis surrouding the spinal cord.,4.3 Radiculo-pial Arteries,These arteries run along the spinal nerve root to the surface of the spinal cord with contribution to the pial coronal network and its centripetal supply. It has not obvious ascending and descending branches and does not form a hairpin vessel on angiograms which is different from the posterior spinal artery. This group of vessels is important in superselective embolization approaches because of its limited territory which oftern involves the blood supply of spinal AVMs.,5. Regional supply of the spinal cord,It can be divided into 3 regions according to the characteristic of blood supply: 1. Cervical region 2. Midthoracic region 3. Thoracolumbar region,5.1 Cervical Region,It includes the whole cervical spinal cord and the first two thoracic segment. It is supplied by 2-4 anterior radiculomedullary arteries. 1.The first arises from the radiculomedullary artery of the vertebral artery, runs along the C3 nerve root. 2. The second arises from the deep cervical artery and runs along the C6 nerve root, also known as the cervical enlargement artery. 3.The third arises from the first intercostal artery and runs along the C8 nerve root.,These radiculomedullary arteries run a short distance while going into the spinal cord through the dura of intervertebral foramina, with a small inclination and forms an angle of about 60-80o with the anterior spinal artery. There is 3 or 4 posterior spinal arteries in cervical region, hence results in the rich blood supply of the cervical spinal cord.,These radiculomedullary arteries run a short distance while going into the spinal cord through the dura of intervertebral foramina, with a small inclination and forms an angle of about 60-80o with the anterior spinal artery. There is 3 or 4 posterior spinal arteries in cervical region, hence results in the rich blood supply of the cervical spinal cord.,5.2 Midthoracic Region,It consists of the first 7 segments of the thoracic spinal cord. There is only one anterior radiculomedullary artery which runs along the nerve root of T4-7. In 15% of people there is absent of the posterior radiculomedullary artery above this level of the anterior radiculomedullary artery; and below this level, with only 1 posterior radiculomedullary artery for every 2 segments.,Midthoracic Region,The blood supply is poor in this region, sometimes the anterior longitudinal spinal axis may be interrupted.,5.3 Thoracolumbar Region,From T8 to conus medullaris. The anterior spinal arteries mainly originate from the Adamkiewicz artery. The Adamkiewicz artery arises from the left side in 80%, 75% from T9-T12, 15% from T5-T8, and 10% from L1-L2 nerve roots. Adamkiewicz artery has the longest path, it divides into the ascending and descending branches when reaching the ventral median fissure, the descending branch is larger and curved .,Thoracolumbar Region,There is 1 or 2 radiculomedullary artery from the lumbar arteries. Iliolumbar arteries or the lateral sacral artery, running along the filum terminale. The posterior radiculomedullary artery at the thoracolumbar region is well developed, but the main supply is from the anterior spinal arteries.,6. Compensatory circulation in various regions,Due to the fact that spinal cord receive its blood supply from 2 groups of vessels, in certain areas, there may be inadequate blood supply or inadequate anastomosis between these vessels, for example, T1 to T4 (especially T4) and ventral side of L1, which are called dangerous area. These area are prone to be injured in clinical situations. There may be formation of collateral anastomosis plexus when there is inadequate blood supply or interruption of the anterior longitudinal spinal axis in the cervical and thoracolumbar region.,6.1 Cervical spinal cord,If there is occlusion of the main arterial trunk (subclavian or vertebral artery), the upper 1/3 of the cervical cord can be supplied by reverse flow from the circumferentical anastomosis formed by the muscular branch of the vertebral artery, muscular branch of the deep cervical artery, ascending cervical artery, occipital artery and the posterior inferior cerebellar artery. The lower 1/3 can obtain blood from the superior and inferior thyroid artery, deep cervical artery and the internal thoracic artery.,6.2 Thoracolumbar segments,When there is occlusion of the Adamkiewicz artery, the spinal cord can obtain it blood supply from the anterior and posterior lumbosacral radiculo medullary artery through the anastom