If the arterial vascularisation of the osseous and muscular envelopes of spinal cord is rich since it comes from multiple metameric arteries, the arteries of the spinal cord which are rather delicate, are a different case in point. 
Indeed, the whole of the spinal cord is fed  by  only 6 or 8 anterior radiculo-medullary arteries  (leading to1 anterior spinal axis) and a score of posterior radiculo-medullary arteries (leading to the postero-lateral spinal axes).  The provision of vascularization of the osseous envelopes and musculo-ligaments of spinal cord is simpler since only two cervical and dorso-lumbar areas can be distinguished.
 
 

At this level, vertebro-medullary vascularization is ensured by the ascending branches of the right and left subclavian arteries : lower thryoidian artery, ascending cervical artery, depp vertebral and cervical artery. 
These are organized in 3 axes : 1 / anterior cervical  or pre-vertebral ( lower thyroidian and mid cervical ascending artery) / latero-vertebral (vertebral) and / posterior (cervical deep).
These 3 axes are largely anastomosed between each other by peri-vertebral horizontal or intrarachidian ramus which ensure the vascularization of the vertebrae. 
Thus, the vascularization of the body of the cervical vertebrae is ensured by branches coming from the thyroid arteries, the ascending and vertebral cervicals arteries and the posterior arc through the deep vertebral cervical arteries.
It is at the cervical level that the anterior spinal axis receives the most afferent arteries (13 to 4).
 
 

- the radiculo-medullary artery does not usually exist in the high cervical area (C1 to C3) 
and the afferents to the anterior spinal axis come from the joining of 2 spinal arteries developing from the end of each vertebral artery.
- at the mid and lower cervical level the anterior spinal axis is fed by 2 to 4 anterior radiculo-medullary arteries developing indifferently on the right or the left of the vertebral artery or the deep cervical artery, or exceptionally from the ascending cervical artery or directly from the subclavian artery. 
Generally, there are 2 principal radiculo-medullary arteries, one developing from the vertebral artery compared to the C5-C6 or C4 -C5 lateral foramen and an an artery developing from the deep cervical artery and penetrating into the rachidian channel through the C7-D1 lateral foramen. 
This artery ensures the vascularization of the cervical spinal cord but can be replaced by a radiculo-medullary artery coming from the vertebral and satellite artery of the 6th cervical root.
The posterior spinal axes are spindly and are fed by 4 to 6 very fine posterior radiculo-medullary arteries coming from the vertebral artery between C3 and C6.  At this level, the possibilities of substitution in the event of occlusion of one of the radiculo-medullary arteries are generally good, the rarity of medullary accidents observed at the time of atheroma or therapeutic occlusions of the vertebral artery.
 
 

DORSAL AND LUMBAR AREA

The vascularization of the rachis and spinal cord is ensured by the intercostal arteries and lumbar exiting in pairs from the dorsal face of the aorta.

1-VASCULARIZATION OF THE RACHIS:

- VASCULARIZATION OF BODY VERTEBRAL: 

-  COSTO-VERTEBRAL VASCULARIZATION :

-VASCULARIZATION OF POSTERIOR ARC :

2-VASCULARIZATION OF SPINAL CORD:

If the provision of the vascularization of the rachis is identical on the whole to that of the dorsal and lumbar rachis, it is different to the vascularization of spinal cord where it is necessary to distinguish after Lazorthes, two distinct upper and middle dorsal and dorsal-lumbar regions .
-Upper and middle dorsal (D3 to D7):

This This region is thus characterized by its poor vascularity and therefore its greater fragility.  In all this area, there is only one anterior radiculomedullary artery. It usually comes  from the posterior dorso-spinal branch of the 4th or 5th intercostal artery, more often on the left ( in 80 % of  cases) than on the right.
The posterior radiculo-medullary arteries are themselves little developed and vary in number, from 4 to 9. 
They come from the  dorso-spinal branch of the intercostal artery, after the crossing of the nerve root, skirt its posterior face, then cross the dura mater and move up and inside to the posterior collateral sulcus where they join the posterior spinal axis.
The frequent existence of a common trunk of the 4th and 5th intercostal right artery and the bronchial artery of the lower right lobe must be pointed out. 
In certain cases, this trunk can provide the anterior radïculo-medullary artery of the dorsal segment and this anatomical provision is certainly responsible for neurological complications which could be observed with the waning of embolization  of the bronchial arteries. 
Lastly, when speaking about anatomical variations, it is necessary to point out the possibility of partial or total vascularization of the upper dorsal region by branches of the sub-clavian artery.
 
 

-DORSO-LOMBAR TERRITORY: 

When its origin is  located on a low level, below D12, an anterior middle dorsal radiculomedullary artery is often found, coming from the 7th or 8th intercostal artery. It is not exceptional, in particular in  children or the adults, to observe the presence of one or two extra , anterior radiculo-medullary arteries in the lower dorsal area.
The posterior radiculo-medullary arteries (posterior spinal) are well developed at this level, and between 4 and  8 can usually be counted. Two of them, which are more developed, are constant : these are the posterior spinal arteries of the cone. They  usually emerge between D12 and L3 and are anastomosed with the ending of the Adamkiewicz artery to form the anastomotic conus arteriosus.
 
 

Finally,  the presence of very spindly radicular arteries, satellites of the lumbar roots,  which could provide for the vascularization of the final cone in the event of occlusion of the Adamkiewicz artery, must be pointed out.

There are very few  studies concerning the medullary venous return. 
Their anatomical position approaches that of the arteries : indeed, the intramedullary veins run into the anterior and posterior peri-medullary plexus. These drain into medullary-radicular veins and, from there, into the intrarachidian plexuses.
 

MEDULLARY VENOUS NETWORK 

This  is made of central veins which present a radiating position and run directly or via horizontal peri-medullary veins into 2 principal veins, the anterior spinal vein and the posterior spinal vein , whose gauge and tract are very variable, however the most frequent position deserves mention :
- the anterior , median and rectilinear spinal vein, leads into the anterior middle sulcus and drains the front quarter of spinal cord. This vein appears to be continuous from the cephalic extremity to the caudal extremity of the spinal cord ;
. - the posterior  spinal vein is sinuous and follows both sides of the centre line, its gauge is more significant than that of the forementioned vein and it is often bulkier at the level of the lumbar or cervical bulge. Lastly, it should be noted that this vein can be duplicated in the cervical area. This vein drains the back three-quarters of spinal cord.
 
 

EFFERENT VEINS 

These are formed from a varying number of the anterior and posterior medullary-radicular veins. Usually, there are 2 or 3 medullary-radicular veins in the cervical area, one at the upper dorsal level, one at the middle dorsal level, 2 at the level of the cone and 1 in the lumbar area ( filum vein). These veins run into the intrarachidian plexuses in comparison with the lateral foramen.
 

EMBOLIZATION
 

MECHANISM

The aim of  vertebral embolization  is  to significantly reduce  hypervascularisation related to the angiogenesis of tumoral origin.
The appearance of one tumoral necrosis results from embolization  if all the pedicles taking part in  neovascularization are treated.
The interest is threefold :
It can allow, through the reduction of bleeding during the operation, for an easier handling  of
certain primitive hypervascular tumours of the rachis or of  hypervascular metastases (kidney, thyroid...), by significantly reducing the bleeding of these lesions during the operation.
Through the tumoral necrosis that it leads to,  embolization  results in a reduction in the mass compression brought about by tumoral invasion and sometimes allows for a partial or complete lifting of a nervous compression beyond the reach of other therapeutic resources like  surgery or  radiotherapy.
Finally and undoubtedly related to the two forementioned mechanisms, embolization  can significantly attenuate the vertebral pains related to tumoral invasion.

One can, in certain circumstances, in particular for secondary lesions which are not numerous (one or two), and of a slow evolution, associate an intra-arterial local chemotherapy by carrying out a chemoembolization . The interest of chemotherapy in this case for lesions considered to be chemosensitive is to locally bring a significant concentration of  alkylant type cytostatics or anthracyclines within the tumour using weak concentrations  compared to the amounts injected for an intravenous treatment.  
This leads to a better clinical tolerance and a reduction in side effects particularly effects on full blood count.  It should be remembered that the intra-arterial administration of cytostatic must come within the framework of procedures which have already been used and after multidisciplinary consultation since this treatment falls outside the scope of the AMM for the products mentioned.
 

TECHNIQUE

This technique is common to the diagnostic vertebromedullary angiography and thus shares these main principles.  
Thus it relies on a perfect knowledge of the arterial and venous vertebromedullary vascular anatomy.  
The advantages, the drawbacks and the risks of this technique will have been explained to the patient beforehand.
An assessment of clotting time, a full blood count and an ionogram are essential to avoid all risks of bleeding and renal insufficiency, considering the volume of iodine injected, and to ensure the absence of red or white blood cell depletion before a possible chemoembolization  . 
Of course if necessary medication to prevent any allergy will have been given beforehand.
The examinations are preferably carried out under neuroleptanalgesy.

The catheterization is usually done by a femoral artery way (seldinger) and an initiator adapted to the gauge of the catheter is used (5F generally). This initiator allows for catheter to be changed, something which can sometimes be frequent considering the variations in the access to the intercostal or lumbar arteries.
The length of the treatment leads to the use of a continuous system of rinsing the initiator and of any coaxial system introduced into the patient's vascular network at the risk of embolic migration or occlusion of  the carrying catheter in particular the microcatheters.
An angiographic cartography is highly desirable with the aim of locating the anterior or posterior  spinal artery before any embolization  treatment.
The principle of STABILITY of the catheter on the level of an intercostal or lumbar is fundamental in avoiding any migration of occlusion particles towards the aorta and its branches.
Thus the choice of the catheter is adapted to the shape of the catheterized vessels to ensure an introduction of the catheter well beyond the arterial ostium. If the catheterization remains limited a microcatheter will be used to reach the distality of the artery to be embolised.
 

It is imperative to respect the anterior and posterior radiculo-medullary arteries.
Once in place a high quality angiography  is carried out to check one final time the absence of arterial branches destined for the spinal cord or dangerous anastomosis.
 

After each sequences of embolization an angiographic control is necessary in order to eliminate the appearance of dangerous anastomoses which can appear with the disappearance of the phenomenon of theft of tumoral hypervascularization. It is often necessary of embolize both sides as well as the levels just above and just under considering transverse and cranio-caudal anastomoses.

MATERIEL

The The catheter used must be adapted to the configuration of the branches being catheterized.
The most commonly used are those known as COBRA which  can have various curves (type I, II, III). For the low lumbar arteries and the branches destined for the rachidian of the hypogastric artery, the counter curve of the catheter can be used to transform them into SIMMONS.
 

Microcatheters are sometimes essential if you want to avoid any risk of backward flow.  
The Mag 2F-3F replaced recently by Magellan can be quoted.  
The most used occlusion agents are particles of Ivalon (ultra Drivalon) gauged into 150 -250, 250-500 microns, Embospheres and sometimes free coils (to treat a carrier trunk).

Digitalization is interesting because it gives a very good quality of imagery by subtraction,  and reduces the amounts of iodine tracer injected, with a reduction of the time of the examination.
 

COMPLICATIONS

Complications are slight when the treatment is  carried out by experienced hands, since the major risk is the embolization  of an artery destined for the spinal cord and  the precautions mentioned previously fortunately mean that this risk  is rare.  
The other complications are in connection with the point of puncture like a hematoma or the femoro-femoral arteriovenous fistula.

INDICATIONS

The indications must be given within the framework of multidisciplinary meetings bringing together cancer specialists, radiotherapists, surgeons and radiologists.
They concern  secondary hypervascular lesions like metastases of thyroid cancer, renal cancer, melanomas or of pheochromocytomas.
 

They can also relate to primitive lesions considered to be hemorrhagic during surgical approach (Tumours with giant cells, vertebral angiomas, benign osteoblastomas , aneurismal bone cysts).

The goal of the angiography is to indicate the hypervascularization, to locate the anterior spinal axes and to allow the embolization to finally be carried out.