1. Dr. Walid El Gaddafi PGY2,NSX
SPINAL AVM / FISTULA
Dr. Walid El Gaddafi
PGY2,NSX

2. INTRODUCTION
Spinal cord vascular malformations (arterial and venous) represent a heterogenous group of blood vessel disorders that affect the spinal cord parenchyma either directly or indirectly.
This group consists of;
spinal arteriovenous malformations (AVMs),
Dural arteriovenous fistulas (AVF),
Spinal hemangiomas,
Cavernous angiomas,
Aneurysms. .
MRI and angiography, have provided further insight into the anatomy and pathophysiology of these lesions.

3. TYPES
In 1992, Anson and Spetzler classified spinal cord vascular malformations into the following 4 categories;
Type 1: This is a dural AVF that arises at the dural nerve root sleeve and is the most common type of malformation,
These malformations are created when a single arterial feeder develops a fistula to the spinal venous circulation.
Pts with type 1 malformations become symptomatic because the AVF creates venous congestion and hypertension, resulting in hypoperfusion of the spinal cord.
Most occur spontaneously, but up to 40% may be traumatic.
These lesions are most frequently found in men between the fifth and eighth decades of life.

5. Type 2:
Glomus AVM, consist of a tightly compacted grp of arterial and venous vessels (nidus) inside a short segment of the spinal cord
The abnormal vessels are intramedullary in location.
Usually in younger pts with acute neurologic deterioration secondary to their location, which is usually the dorsal cervicomedullary region.
The mortality rate related to type 2 malformation is reported at 17.6%. After initial hemorrhage,
The rebleed rate is 10% within the first month and 40% within the first year.

7. Type 3:
These malformations are arteriovenous abnormalities of the spinal cord parenchyma fed by multiple vesseles
Both intramedullary and extramedullary in location.
Young adults and children.

8. Type 4:
These malformations are intradural extramedullary AVFs on the surface of the cord that result from a direct communication between a spinal artery and a spinal vein without an interposed vascular network.
Third and sixth decade of life.
Spinal vascular malformations can also be classified into 2 general groups. One group consists of the spinal dural fistulas (type 1), and the other group has intradural pathology (types 2-4).

9. HISTORY AND PRESENTATIONS
AVMs have been recognized as a potential cause of myelopathy for more than 100 years.
In 1914, Charles Elsberg performed the first successful operation on a spinal cord malformation.
In the 1960s, significant advances were made in the techniques of spinal angiography, which produced further understanding of normal spinal vasculature and the pathophysiology of spinal cord malformations.
Kendall and Loque used these modern imaging modalities to define a distinct subgroup of spinal AVMs classified as dural spinal AVFs.

10. In 1977, Kendall and Loque treated these lesions with the less-invasive technique of directly ligating the fistula origin along the dural sleeve, with good results.
The treatment of spinal cord malformations is being further expanded with the use of interventional neuroradiology.
With further improvements in spinal angiography and endovascular techniques or as a complement to open microsurgical techniques.

11. Eitiology
The etiology of AVMs of the spinal cord has not been clearly defined.
Intradural parenchymal malformations arise in a younger pt population and are believed to be congenital. However, spinal arterial dural fistulas commonly arise in an elderly population and are believed to be due to a traumatic occurrence.
These AVF malformations develop near a spinal dural artery, forming an abnormal arteriovenous communication with the venous circulation.

12. PATHOPHYSIOLOGY
Spinal malformations can be separated into 2 subgroups.
The first subgroup is spinal AVFs, which are believed to be acquired lesions.
They represent an abnormal connection between the spinal radicular artery and the medullary vein of the spinal cord.
This fistula creates a slow-flow vascular malformation that typically develops over months to years.
The high-pressure arterial flow from the radicular artery dilates the medullary venous system and results in venous stasis.

13. Venous outflow obstruction then impairs the neural circuit because the spinal cord parenchyma is being hypoperfused.
Neurologic compromise is thought to occur secondary to this venous engorgement and to the resulting spinal cord ischemia.
The second subgroup is spinal intradural AVMs, which are congenital lesions that consist of abnormal vasculature.
These lesions recruit arterial blood vessels and have thin-walled venous vessels.
Hemorrhage occurs when the high-flow arterial system overcomes the capacity of the abnormal venous vessels.

14. CLINICALLY - TYPE 1 Pts with AVFs are typically older than 40 years.
AVFs occur more frequently in males than in females.
Symptoms increase over an extended period of months to years and include progressive weakness of the legs and concurrent bowel or bladder difficulties.
Painful radiculopathy may be present.
Foix-Alajouanine syndrome is an extreme form of spinal dural AVF that affect a minority of pts who present with a rapidly progressive myelopathy due to venous thrombosis from spinal venous stasis.

15. TYPE 2-4
Younger than 30 years and presents with a subarachnoid or intraparenchymal hemorrhage and, mass effect on the spinal cord.
Patients with spinal intradural malformations typically present acutely either after intraparenchymal or subarachnoid hemorrhage.
Pts with SAH may experience sudden onset of a severe headache, meningismus, or photophobia.
A spinal AVM should be considered in the differential diagnosis of any pt with a SAH who has negative cerebral angiography results.

16. If the hemorrhage is intraparenchymal, the pt presents with sudden neurologic deterioration, a sudden onset of pain, and a distinct spinal level of neurologic dysfunction.
Lastly, pts with intradural lesions can present with mass effect caused by growth of the AVM.
The enlargement of the vascular malformation compresses the surrounding neural tissue, impairing neurologic function.
These intradural spinal vascular malformations (types 2-4) develop during embryogenesis and, therefore, are present in an even distribution throughout the spinal cord.

18. ANATOMY
Physical examination findings and the type of spinal malformation are as follows:
Bruit over spinal cord - Intradural AVM
Hyperreflexia caudal to lesion - Dural AVF and intradural AVM In order to understand and treat these arterial and venous malformations, knowledge of the normal spinal cord vascular supply is imperative.
The aorta contributes to blood flow through the segmental arteries, which, in turn, supply the spinal medullary and radicular arteries.
The radicular artery provides circulation to the nerve root dural sleeve. This is the artery typically involved in the formation of a spinal arteriovenous fistula (AVF) by its connection to the medullary spinal veins.

19. This medullary artery bifurcates into anterior and posterior divisions, which then merge and form the spinal arteries. The spinal cord has 3 main spinal arteries (1 anterior and 2 posterior), which parallel the spinal cord.
Upper motor signs - Dural AVF and intradural AVM
Weakness - Dural AVF and intradural AVM
Increased tone - Dural AVF and intradural AVM
Saddle region sensory disturbance - Dural AVF
Gait disturbances - Dural AVF

20. The blood supply to the spinal cord can be divided into 3 anatomic regions:
The first is the cervicothoracic region, which receives segmental blood vessels from the vertebral arteries and the great vessels of the neck (ie, aorta, subclavian and carotid arteries).
The second is the midthoracic region, which receives most of its segmental blood supply from the aorta.
This region of the spinal cord receives most of its blood supply from collateral circulation (superior and inferior arteries) and, therefore, is susceptible to infarction.

21. The third is the thoracolumbar region, which receives segmental vessels from the abdominal aorta and the iliac arteries.
The largest segmental vessel, the artery of Adamkiewicz, may be variably located between levels T9 and L2 and, in most cases, arises from the left side of the vertebral column.
The venous plexus in the spinal column, the Batson plexus, is unique compared with other venous plexuses in the body.
This network of venous vessels does not have valves and thus does not prevent retrograde venous flow. Therefore, this valveless system allows an arterial fistula from the radicular artery to create congestion through the entire venous plexus, which can manifest as spinal cord ischemia.

22. INVISTIGATIONS
CT scanning may demonstrate dilated vessels in the thecal sac, but findings are usually normal.
If a pt presents with symptoms of SAH, CT scanning demonstrates blood in the spinal fluid.
Myelography findings, with or without CT, show dilated vessels in the intradural space.
This imaging modality is very sensitive and shows these abnormalities in detail.
This is an invasive procedure that requires injection of a contrast agent into the thecal sac. Postprocedure headaches are not uncommon.

23. MRI is a noninvasive imaging modality.
The soft tissue and neural elements are visualized in detail with this technique.
Dilated intradural vessels can be seen as flow voids or can be seen filling with contrast. Edema or hemorrhage in the spinal cord parenchyma can be assessed. The exact fistula site cannot be localized.
Arteriography is the criterion standard modality for visualizing AVMs.
This is a dynamic study that allows visualization of the pathology in real time, allowing assessment of high-flow versus low-flow AVMs. In addition, the location of the fistula can be visualized.
It is an invasive procedure that may cause morbidity such as spinal cord ischemia, cerebral vascular accident, and vascular dissection

26. MEDICAL TREATMENT
Presently, no acceptable pharmacological means are available to treat spinal vascular malformations.
The use of glucocorticoids may improve the pt's neurologic function for a short period.
These steroids decrease vasogenic edema, but they do not treat the underlying pathology of the disorder.

27. SURGICAL TREATMENT
Each spinal vascular malformation is a unique lesion; therefore, an individualized treatment algorithm must be tailored to each pt.
The present surgical treatment options include open surgical ligation or resection of the malformation, endovascular occlusion, spinal radiation, or a combination of these techniques.
Dural arteriovenous fistulas (AVFs), type 1, can be treated with either open or endovascular ligation.
Both techniques yield excellent results, with occlusion rates reported as higher than 80%.

28. The benefit of the endovascular technique is that it is less invasive.
If the pt has multiple sites of fistula formation, open ligation is more appropriate because all feeding vessels may be ligated under direct vision.
Open surgery is necessary if the arterial feeding vessel is impossible to access because of tortuous vascular anatomy or if the vessel supplies blood to healthy regions of the spinal cord.
Intradural AVMs (types 2-4) are typically best treated with endovascular surgery and, if required, open surgery and resection.

29. ENDOVASCULAR TREATMENT
Treatment options are dictated by the location of the lesion, the pt's medical condition, and the risk-versus-benefit ratio.
The most important factor in determining treatment options is the presence of intramedullary or extramedullary shunting.
Malformations that are subpial in location are less likely to be cured. These are usually supplied by subcommissural branches of the anterior spinal artery (ASA).

30. The role of partial embolization is not clear.
Long-term clinical results in pts with symptomatic spinal AVMs have demonstrated a lower incidence of recurrent hemorrhage; this may have a role in difficult lesions.
Lesions on the surface of the spinal cord that are supplied by circumferential branches of the ASA may be safely treated with either embolization or surgery.

31. The new generation of liquid embolic material and microcatheters has made interventional treatment of spinal AVMs safer, with better results.
The goal of any intervention is to eliminate the shunt.
Microcatheterization is of paramount necessity in achieving effective results.
Delivery of embolic material to the nidus of the lesion reduces the AVM and reduces the risk of inadvertent embolization of normal vessels.

32. The authors' agent of choice is n-butyl cyanoacrylate (n-BCA).
Embolization of lesions supplied by the ASA requires selective catheterization and deposition of embolic material.
Permanent deficits due to embolizations in the ASA territory occur in up to 11% of pts (Veznedaroglu, 2006).
In higher-flow lesions, pharmacologically induced hypotension is used, typically with a mean arterial pressure of 50 mm Hg. With larger draining vessels, the Valsalva maneuver also helps to delay transit time.
When preoperative embolization is planned, polyvinyl alcohol microparticles (PVAs) are a reasonable choice of embolic material.

33. They are also useful for embolization of type 2 AVMs.
The advantages of PVA are that embolization may be performed at a more proximal location and that the size of particle can be determined depending on the size of the lesion and its collaterals. The goal of treatment with either agent is to provide distal occlusion of the nidus.
Proximal occlusion results in collateral reconstitution, with little hope of cure.
Regardless of the choice of material used for embolization, all procedures should be performed under general anesthesia with neurophysiologic monitoring, depending on the location of the lesion.
Somatosensory-evoked potentials (SSEPs) are very accurate in assessing spinal cord function. Motor-evoked potentials (MEPs) are also useful when a spinal AVM is supplied by the ASA.

34. INTRAOPERATIVE
Once the lesion has been defined and the surgical treatment plan (either endovascular, open surgical, or a combination of the two) is determined, the patient is taken to the operating room or endovascular suite.
The procedure is performed with the patient under general anesthesia, with the use of neurophysiological monitoring.
Intraoperative monitoring allows analysis of ischemia to the spinal cord so that normal vascular channels are not inadvertently permanently disturbed.
Arteriography may be performed in the operating room, with either endovascular or an open technique to confirm closure of the fistula.

35. POSTOPERATIVE
The patient is awakened from anesthesia and taken to a monitored setting where serial neurologic examinations can be performed. With ligation of the dural AVF, most patients show neurologic improvement and can begin physical therapy. Improvement in neurologic examination findings may take several weeks.
If arteriography was not performed in the operating room, it should be performed in the immediate postoperative period to document closure of the fistula.

36. FOLLOW UP
Pts should be monitored with serial neurologic examinations and imaging studies in an outpatient setting to confirm closure of the fistula.
With intradural lesions, a procedure is deemed successful based on intraoperative assessment of complete resection and a postoperative arteriogram that shows no arteriovenous shunting.
If patients experience any worsening from their neurologic baseline, an appropriate evaluation with imaging studies is completed to rule out fistula recurrence.

37. RISKS OF SURGERY AND ENDOVASCULAR
Skin infection or cellulitis
Bleeding
Injury to nervous tissue, causing paralysis, bladder or bowel dysfunction, or sexual dysfunction
Chronic pain syndromes
Thrombosis of epidural veins and neurologic loss
Recurrence of fistula
Spinal cord infarction

38. COMPLICATION POST SURGERY
Infection of meninges (meningitis)
Cerebrospinal fluid leak
Wound dehiscence

39. COMPLICATION POST ENDOSCOPIC
Femoral hematoma
Pseudoaneurysms and thrombosis
Arterial dissection

40. OUTCOME
Pt outcome is directly related to neurologic function at the time of the surgical intervention.
Pts who are able to ambulate when treated tend to remain ambulatory and may increase their strength with physical therapy.
Pts who do not have antigravity strength in the lower extremities before treatment are unlikely to regain neurologic function to the point of ambulation.
Pts who present with bowel or bladder dysfunction have a limited return of neurologic function.
Diagnosing these lesions early and providing appropriate treatment is important if patients are to achieve an optimal neurologic outcome.

41. FUTURE
MRI should be the first diagnostic modality performed when a spinal vascular malformation is suspected.
If a lesion is found, spinal angiography is considered the criterion standard for optimal analysis of the angioarchitectural features.
Embolization with a liquid embolic agent is the first-choice treatment for types 2-4 malformations, whereas surgery may be a better option for type 1 malformations.
The prognosis of these lesions seems better than previously thought, especially with advances in endovascular techniques and new embolic agents that offer a high success rate with low morbidity.

42. Further advances in endovascular and microneurosurgical techniques will be made in the future.
Advances in endovascular techniques and equipment should include smaller and more navigable catheters that can be manipulated through tortuous anatomy.
The use of noninvasive techniques, such as stereotactic spinal radiosurgery, is presently being investigated.

43. THANK YOU