Fig. 8.1
Lateral non-subtracted and subtracted angiograms (a, b) show the course of anterior spinal artery (white arrows) emerging from the cisternal segment of the vertebral artery and descending on the anterior surface of the spinal cord. Odontoid arch anastomosis (red arrowheads) is one of the common connections between vertebral artery and ascending pharyngeal artery, branch of the external carotid artery. AP and lateral subtracted views (c, d) show a radiculo-medullary artery at C3 level feeding the anterior spinal artery
This basic anatomy must always be kept in mind when approaching any vascular lesion of this system and even more when switching to any kind of endovascular treatment.
Occlusion of spinal arteries is obviously to be avoided, since the risk of causing an infarct and a severe medullary syndrome is high, much higher for the anterior axis, though, compared to the posterior arteries, because collateral circulation is unlikely to work if the occlusion is inside the axis itself, caused by injection of solid or liquid embolics.
From a pragmatic point of view, for local lesions involving one or two vertebral bodies in the dorsal or lumbosacral segments, it is probably enough to visualize some metameres above and below the lesions, to be sure to image all the possible feeders to the lesion together with the spinal arteries.
For more extensive diseases or when dealing with vascular malformation (AVMs, direct or dural fistulas, etc.), a complete examination must be accomplished.
Differently, anatomy and vascularization of the cervical spine are more complex. Caudal cervical bodies are fed by branches arising from the tireocervical arteries, whereas the median vertebrae are fed by arteries of the costocervical trunk.
The C1-C3 segment is vascularized also by vessels coming off the occipital artery. But anatomic variations are very frequent, so that imaging of all these arteries is needed before taking any diagnostic and therapeutic decision.
The extremely rich arterial network of the head, face, and neck makes it mandatory to check for possible collaterals, linking arteries of the external carotid to the vertebro-basilar and cervical medullary system.
If an endovascular treatment is planned, attention must be paid to possible nontarget embolization of the brain [5].
8.1.3 Endovascular Treatment
After transfemoral puncture, the diagnostic part of the procedure requires the choice of a correct catheter. Different curves are available, in accordance with the personal experience but also the diameter of the aorta, the presence of atheromatous plaque, and even its possible aneurysmatic dilation.
Djindjan, Simmons, Cobra, Headhunter or special (custom) curves are generally used.
Of note, the possibility to steam shape the catheters is often very useful to negotiate difficult origin of intercostals and lumbar arteries and large diameter aortas.
For presurgical procedures, once the diagnostic phase has shown a significant pathologic blush at the level of the tumor, injection of particulate embolic agents is almost always enough to obtain a useful and reasonably stable devascularization in the next 48–72 h, allowing the surgeon to perform a safer operation.
Different issues and concerns must be taken into consideration when it comes to the presurgical treatment of vertebral tumors.
The kind of surgery (debulking, “standard” resection, en bloc resection, and local stabilization, etc.) may require a different rate of devascularization, and the high flow shunts inside the tumoral tissue may need different embolic material and devices.
In our experience the use of PVA particles in the range of 150–350 microns of diameter results to be easy, safe, and effective.
Injection is realized at different dilution of the particles, according to operator’s experience, until the flow in the feeder is almost absent and the pathological blush not visible anymore (Fig. 8.2).
Fig. 8.2
Seventy-four-year-old woman with renal carcinoma’s metastasis in C7 undergoing a preoperative endovascular treatment. Post-contrast axial T1-weighted (a) and sagittal T1-weighted (b) images show involvement of the posterior arch by the metastasis with compression of the spinal cord. DSA AP view (c) demonstrates the high vascularization of the lesion fed by branches of both the tireo-cervical trunks. AP angiogram (d), immediately after the embolization with PVA particles, shows a consistent reduction of blood supply in the lesion
Angiographic runs have to be taken at intervals during the procedure, to check for the state of the flow and especially for the appearance of spinal arteries or for collateral circulation, since the lesser the flow, the more likely the injection can open and jeopardize these vessels.
These particles tend to aggregate, thus occluding vessels larger in diameter than nominal and probably in a less homogeneous mixture [6].
On the other side, when using more recent products, such as calibrated microspheres, attention must be paid to oversize the diameter of the particles compared to PVA, because these embolics do not aggregate, are compressible and consequently injectable through smaller catheters compared to their nominal size, and, moreover, are very slippery and elastic, making it possible to easily pass through AV shunts and reach the venous drainage or, more risky, embolize collaterals as soon as they open: all these potential sources of complications will not be visible during fluoroscopy.
The use of liquid embolics, such as glue, Onyx, Phil, and solid materials as coils, has a very limited role in the treatment of vertebral tumors, unless a large mass has to be treated in a relatively safe anatomical region, like the sacral area (Fig. 8.3).
Fig. 8.3
Sixty-year-old patient presenting with progressive paraplegia, bilateral limb numbness, and back pain. MR images (a, b, c) reveal a huge mass of the sacrum with posterior extension to spinal canal and sacral foraminae. A-P angiographic runs (d, e, f) show high vascularization of the lesion with drainage into a vein inside the spinal canal. Patient undergoes a preoperative embolization (g, h) of the lesion with Onyx and with PVA particles with reduction of blood supply of the lesion. Non-enhanced CT (i) shows the results of the endovascular procedure
In other territories, the more complex procedure, even considering the higher stability of the devascularization, doesn’t seem to carry a consistent benefit in the presurgical approach [7].
Even if no randomized trial has been designed so far to show the usefulness of presurgical embolization in reducing intraoperative blood loss, this approach is widely accepted and many series support this concept [7].
Conceptually and technically, things are different when the anatomical region involved is the proximal cervical spine and when the lesion is large, thus not only entering the spinal canal but also surrounding one or both vertebral arteries.
In some of these cases, after considering histology, age, and comorbidity, an en bloc resection could highly improve patient’s prognosis or even be the only possible solution, other than palliative surgery or embolization.
In these cases, PVA embolization needs very careful injection because the risk of nontarget embolization in this region is consistent, thus making it obligatory a preliminary six-vessel study (vertebral arteries, internal and external carotid of both sides) [8].
A less common requirement from the surgeon is the occlusion of one or even both vertebral arteries. Occlusion of the vertebral artery on one side (Figs. 8.4 and 8.5) at the distal cervical segment (C1-C2 level) can be easily accomplished, provided that the contralateral artery has a sufficient caliber, up to the vertebro-basilar junction, to provide blood flow for the basilar and the branches coming off it and also to feed the contralateral PICA, once the omolateral vertebral has been occluded.
Fig. 8.4
Preoperative therapeutic vertebral artery occlusion in a 62-year-old man with the recurrence of a previously operated chordoma of C2 on the left side. Non-enhanced CT images (a, b) demonstrate the chordoma of C2 vertebral body extending to the odontoid process. Patient undergoes a preliminary DSA (c), after which occlusion of the left vertebral is realized with platinum coils (d, e). Right vertebral selective angiogram (f) shows a perfect flow in the basilar artery and a reverse flow feeding the distal left vertebral
Fig. 8.5
Preoperative therapeutic vertebral artery occlusion in a patient suffering from a chordoma of C2. Post-contrast MR images (a, b, c) show a chordoma of C2-C3-C4 extending to the anterior and paraspinal soft tissues. Non-enhanced CT (d) better defines the erosion of the vertebral bodies. Patient undergoes a preliminary DSA (e, f), showing that both vertebral arteries, of good caliber, reach the basilar artery, thus allowing occlusion of the right one. Frontal single shot radiographs (g) and left vertebral artery selective angiogram (h) demonstrate the occlusion with platinum coils of the extracranial vertebral artery with good supply of posterior fossa circulation from left vertebral artery
If these criteria are respected, then it is possible to go on with the occlusion deploying detachable platinum coils, which best fit the need of the surgeon.
No clinical test occlusion is feasible nor needed at this level.
A reliable neurological examination would be impossible, since posterior fossa symptoms are often subtle and need complex movements and orders to be investigated. Moreover, angiographic evaluation, as for the carotids, has proved to be highly reliable and very easy to obtain.
More unusual is bilateral vertebral occlusion, more likely to be feasible in young patients (Fig. 8.6).
Fig. 8.6
Thirteen-year-old girl with an osteosarcoma of C2-C3 extending to the paraspinal soft tissues as shown in the MR images (a, b, c). The patient undergoes a preoperative endovascular occlusion of both vertebral arteries (d, e) after performing an occlusion test in order to evaluate the collateral supply from anterior circulation. Right internal carotid selective angiogram (f), acquired after occlusion of both vertebral arteries, demonstrates a good supply of the posterior circulation via the posterior communicating artery. Sagittal MR image shows the result of the reconstructive surgery (g)
It is technically similar, but needing an angiographic balloon occlusion test, to make sure that the patency of the basilar and distal vertebral arteries is guaranteed by the reverse flow through one or two posterior communicating arteries. Provided the flow is consistent, the second vertebral may be occluded with coils, as well.
8.1.4 Anesthesiology
All the procedures can be carried out with patients awake, or with some degree of sedation, also depending on the clinical conditions, age, etc.
General anesthesia might be considered for specific situation, including very long procedures in old patient or patients suffering from untreatable back pain.
In some situation, whenever surgery is planned right after the endovascular procedure, a single anesthesia may be done.
8.1.5 Timing for Surgery
Since the effect of the presurgical treatment with particles is decreasing over time, it is generally accepted that surgery should not be delayed of more than 48–72 h from the endovascular treatment, knowing that the sooner, the better.
8.1.6 Complications
Complications of spinal tumor embolization are low [11].
Apart from those related to any endovascular access, i.e., problems due to vascular access (hematoma or pseudoaneurysm), radiation exposure, and reaction to contrast medium, most serious complications are those connected with the navigation in the metameric and supraortic arteries and with the injection of embolic agents.
Dissection and rupture of arteries is always possible but is a rare evenience.
More frightening, embolization of cerebral territories or spinal arteries can occur, whose rate can be kept low, if a complete study of the vascular territories is performed before injecting embolic material.
And also keeping in mind that the endovascular procedures are preparatory to a main surgery, therefore, morbidity must be kept low also by not pushing too much the technique.
Otherwise, the effort focused on making surgery easier and at lower risks is vanished.
8.2 Part II: Vertebral Hemangiomas Embolization
8.2.1 General Information
Vertebral hemangiomas are extremely frequent in the general population (incidence of 10% to 12%), often solitary (70%) and, less frequently, multiple (30%) [12], mostly involving the lumbar and dorsal spine. They are benign vascular lesions, almost always asymptomatic, and defined as vascular malformations, dysplasias [13], or hamartomas. Only 1% to 2% of these cases cause problems, such as localized pain (symptomatic hemangiomas), fractures, or neurological deficits caused by the growth of a soft extraosseous component [14] invading the spinal canal and thus compressing the spinal cord and/or spinal nerves (aggressive hemangiomas).
Symptomatic hemangiomas, with or without associated fracture, are now effectively and permanently treated with percutaneous vertebroplasty (VP) (Figs. 8.7 and 8.8) gold standard [15]: the complete filling and subsequent sclerosis of the hemangioma result in remission and full recovery [16].
Fig. 8.7
Thirty-two-year-old female, T1-weighted coronal MR scan with gadolinium. Symptomatic vertebral hemangioma (thoracic back pain for more than 1 year) in T8 involving the entire vertebral body, with strong enhancement and minimal involvement of the left paravertebral side (white arrow). There is also a somatic fracture with sinking of both vertebral end plates (black arrows)
Fig. 8.8
AP follow-up radiograph of same patient post D8 hemangioma embolization and percutaneous vertebroplasty PMMA cementing material, highly radiopaque, entirely filled the hemangioma (black arrow); in the left paravertebral side is highlighted (white arrow) the employed coil for the pre-vertebroplasty embolization
Aggressive vertebral hemangiomas sometimes represent a complex diagnostic issue, since they can resemble, both clinically and radiologically, more harmful diseases, such as primary or metastatic bone tumors [17]; in these uncertain cases, performing a percutaneous biopsy under CT guidance or fluoroscopy is mandatory (Figs. 8.9 and 8.10).
Fig. 8.9
Fifty-seven-year-old female, CT sagittal view of the bone architecture demonstrates a lesion in D12, showing structural rearrangement of the vertebral body with large lytic areas (white arrow), also involving posterior vertebral wall (black arrow). Since x-ray images are not pathognomonic, more than one diagnostic hypothesis can be suggested: vertebral hemangioma, myeloma, or another aggressive disease
Fig. 8.10
Same patient of the previous figure. Guided biopsy by CT fluoroscopy, with semiautomatic guillotine 18G needle (black arrow); histology confirms expected diagnosis of aggressive vertebral hemangioma, subsequently treated by percutaneous vertebroplasty
The differential diagnosis for a potential spinal hemangioma includes multiple myeloma, aneurysmal bone cyst, bone metastases, lymphoma, osteosarcoma, and Paget’s disease.
Aggressive vertebral hemangiomas with extraosseous tissue component, classified as Stage 3 according to Enneking [18], grow rather slowly over years or decades. Such growth is not due to mitosis [19] and over the year it will spread in the paravertebral area and/or invade the spinal canal. The consequent compression of nerve root or spinal cord is associated to neurological symptoms, usually progressive [20]. In a few cases, bleeding [21] or thrombosis located in the hemangioma will cause a rapid onset of the neurological symptoms.
Related posts:
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
