Vascular Malformations of the Spinal Cord Treatment & Management

Updated: Feb 17, 2016
  • Author: James S Harrop, MD; Chief Editor: Brian H Kopell, MD  more...
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Treatment

Medical Therapy

Presently, no acceptable pharmacological means are available to treat spinal vascular malformations.

The use of glucocorticoids may improve the patient's neurologic function for a short period. These steroids decrease vasogenic edema, but they do not treat the underlying pathology of the disorder. Unfortunately, these medications have adverse long-term affects. The prolonged use of steroids is associated with adverse systemic effects, such as gastric ulceration, elevated blood glucose levels, and suppression of the immune system.

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Surgical Therapy

Each spinal vascular malformation is a unique lesion; therefore, an individualized treatment algorithm must be tailored to each patient. 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%. The benefit of the endovascular technique is that it is less invasive. If the patient 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. [4, 7, 8, 9, 10, 11]

Intradural AVMs (types 2-4) are typically best treated with endovascular surgery and, if required, open surgery and resection.

Endovascular treatment

Treatment options are dictated by the location of the lesion, the patient'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). The role of partial embolization is not clear. Long-term clinical results in patients 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.

The new generation of liquid embolic material and microcatheters has made interventional treatment of spinal AVMs safer, with better results. [12, 13] 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 arteriovenous malformation (AVM) and reduces the risk of inadvertent embolization of normal vessels.

Liquid embolic agents are the first choice for most spinal AVMs because they are the most likely to fill distal nidus and because they are associated with a low recanalization rate. The authors' agents of choice are n-butyl cyanoacrylate (n-BCA) and Onyx (ethylene vinyl alcohol copolymer). 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 patients. [14]

The manipulation of viscosity of the liquid embolic as in the case of n-BCA or use of different viscosity Onyx (Onyx-18 versus Onyx-34) helps to ensure more precise deposition. Polymerization should occur in transit through the arteriovenous shunt. 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. 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.

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Preoperative Details

The preoperative evaluation consists of a detailed neurologic examination, baseline urodynamic evaluation, and appropriate imaging studies that confirm the diagnosis of a vascular malformation. MRI of dural AVFs on the thoracolumbar junction usually shows serpiginous vessels in the intradural compartment, along with vasogenic edema in the spinal cord (see the images below). Intradural vascular spinal malformations appear as lesions in the spinal parenchyma.

Spinal malformation. This is a sagittal T2-weighte Spinal malformation. This is a sagittal T2-weighted MRI of the thoracic spine of a 68-year-old woman with a 9-month history of back pain and sensory loss, progressing to the point of loss of bowel and bladder function along with a sudden onset of paraparesis. Note the thoracolumbar junction with an edematous spinal cord and dilated serpiginous intradural venous plexus.
Spinal malformation. This is an axial T2-weighted Spinal malformation. This is an axial T2-weighted MRI of the thoracic spine of a 68-year-old woman with a 9-month history of back pain and sensory loss, progressing to the point of loss of bowel and bladder function along with a sudden onset of paraparesis. Note the lumbar spine with an edematous spinal cord and dilated intradural venous plexus.

Once the diagnosis is considered, the anatomy of the malformation can be further defined with spinal arteriography. Spinal arteriography illustrates the detailed anatomy with dynamic images, providing the surgical team the information necessary to decide the best treatment option.

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Intraoperative Details

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.

Recently, indocyanine green videoangiography has been used by some neurological surgery centers during the treatment of spinal dural AVFs. This new technology allows surgeons to view, in real time, the vasculature within the operating field to ensure the AVF has been obliterated. [15]

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Postoperative Details

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.

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Follow-up

Patients 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.

Postoperative MRI findings do not necessarily correlate with clinical outcomes. It is not uncommon for spinal cord abnormalities to persist on MRIs for many months, even with successful treatment. [16]

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Complications

Risks of open surgical or endovascular treatment

See the list below:

  • 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

Complications that result from open surgical ligation or resection

See the list below:

  • Infection of meninges (meningitis)

  • Cerebrospinal fluid leak

  • Wound dehiscence

Complications that result from the endovascular technique

See the list below:

  • Femoral hematoma

  • Pseudoaneurysms and thrombosis

  • Arterial dissection

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Outcome and Prognosis

Patient outcome is directly related to neurologic function at the time of the surgical intervention. Patients who are able to ambulate when treated tend to remain ambulatory and may increase their strength with physical therapy. Patients who do not have antigravity strength in the lower extremities before treatment are unlikely to regain neurologic function to the point of ambulation. Patients 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.

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Future and Controversies

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 type 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.

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.

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