Description
Application of spinal magnetic resonance angiography (MRA) allows for more effective and noninvasive screening for vascular lesions than magnetic resonance imaging (MRI) alone. It may improve characterization of normal and abnormal intradural vessels while maintaining good spatial resolution. Spinal MRA may be used for the evaluation of spinal arteriovenous malformations, as well as injuries to blood vessels supplying the spine and cord.

OVERVIEW
Spinal MR Angiography/MR Venography¹³ — Typically, contrast-enhanced 3D time of flight techniques and contrast-enhanced CT angiography (CTA) are used for evaluation of the spinal arteries, veins, and related pathology as a non-invasive alternative to the gold standard catheter angiography. The detection rate of the Adamkiewicz artery (AKA) by MRA is in the range of 69% – 100%, but with modern equipment both MRA and CTA detection rates should approach 100%.¹¹ Magnetic resonance angiography is well suited to patients who cannot receive iodinated contrast and undergo CTA. CTA has the advantage over MRA of providing greater spatial resolution, can image the entire spine during one contrast bolus, and provides for a faster exam time that is less prone to motion artifact. MRA is limited by a finite field of view, typically ≤ 50 cm.11 MRI has the advantage over CT of detecting areas of ischemia via diffusion weighted imaging. Mathur et al showed a 100% sensitivity in detecting recurrent spinal arteriovenous fistulas post-treatment.²

Spinal Arteriovenous Malformations (AVMs) — Spinal cord arteriovenous malformations are comprised of snarled tangles of arteries and veins that affect the spinal cord. They are fed by spinal cord arteries and drained by spinal cord veins. Spinal dural arteriovenous (AV) fistulas are the most encountered vascular malformation of the spinal cord and are a treatable cause of progressive paraparesis. Magnetic resonance angiography (MRA) can record the pattern and velocity of blood flow through vascular lesions as well as the flow of cerebrospinal fluid throughout the spinal cord. MRA can define the vascular malformation and may assist in determining treatment.⁵

Spinal Arteries/Veins — Vascular malformations, trauma, disc herniations, neoplasms, and coagulopathies or infection causing thrombosis can compromise the spinal cord blood supply and drainage. The spinal cord arterial supply is derived from the anterior spinal artery, posterolateral spinal artery, and the arteria radicularis magna or artery of Adamkiewicz (AKA). The anterior spinal artery supplies the anterior two-thirds of the cord and arises from the vertebral arteries. It receives contributions from the ascending cervical artery, the inferior thyroid artery, the intercostal arteries, the lumbar artery, the iliolumbar artery, lateral sacral arteries, and the AKA. The AKA arises on the left side of the aorta between the T8 and L1 segments, to anastomose with the anterior spinal artery and supply the lower two-thirds of the spinal cord. Two posterolateral spinal arteries arise from the posteroinferior cerebellar arteries and supply the posterior third (posterior columns, posterior roots, and dorsal horns) of the spinal cord. The spinal venous system is divided into intrinsic and extrinsic veins differentiated by their location within the spinal canal or extrinsic to the canal, respectively. They drain into the radiculomedullary veins, subsequently to paravertebral and intervertebral plexuses, then to the segmental veins that eventually drain into the ascending lumbar veins, azygos system, and pelvic venous plexuses.⁶

GENERAL INFORMATION

It is an expectation that all patients receive care/services from a licensed clinician. All appropriate supporting documentation, including recent pertinent office visit notes, laboratory data, and results of any special testing must be provided. If applicable: All prior relevant imaging results and the reason that alternative imaging cannot be performed must be included in the documentation submitted.

Where a specific clinical indication is not directly addressed in this guideline, medical necessity determination will be made based on widely accepted standard of care criteria. These criteria are supported by evidence-based or peer-reviewed sources such as medical literature, societal guidelines and state/national recommendations.
 

Policy
SPINAL CANAL MRA is considered MEDICALLY NECESSARY for the following indications:

INDICATIONS FOR SPINAL CANAL MAGNETIC RESONANCE ANGIOGRAPHY (MRA)

• For the evaluation of spinal arteriovenous malformation (AVM)^1,2,3,4,5
• Myelopathy when the suspected etiology is a compromise of blood flow or drainage to the spinal cord^6,7
• For the evaluation of a known cervical spine fracture, disc herniation, infection, or venous thrombosis where there is concern for vascular pathology (compression or thrombosis) compromising spinal cord blood flow or venous drainage^6,7
• For the evaluation of known or suspected vertebral artery injury when there is also concern for vascular compromise to the spinal canal and its contents (otherwise neck MRA or CTA is sufficient to evaluate vertebral artery injury)^8,9
• Preoperative evaluation (e.g., localization of the spinal arteries prior to complex spinal surgery, aortic aneurysm repair, or characterization of suspected vascular lesion of the spinal canal and its contents)^10,11,12
• A follow-up study may be needed to help evaluate a patient’s progress after treatment, procedure, intervention, or surgery. Documentation requires a medical reason that clearly indicates why additional imaging is needed for the type and area(s) requested.²

Other Indications
 
Further evaluation of indeterminate findings on prior imaging (unless follow up is otherwise specified within the guideline):

• For initial evaluation of an inconclusive finding on a prior imaging report that requires further clarification
• One follow-up exam of a prior indeterminate MR/CT finding to ensure no suspicious interval change has occurred. (No further surveillance unless specified as highly suspicious or change was found on last follow-up exam.)
   

All other uses of this technology are investigational and/or unproven and are therefore considered NOT MEDICALLY NECESSARY.

References

1. Amarouche M, Hart JL, Siddiqui A, Hampton T, Walsh DC. Time-resolved contrast-enhanced MR angiography of spinal vascular malformations. AJNR Am J Neuroradiol. Feb 2015;36(2):417-22. doi:10.3174/ajnr.A4164
2. Mathur S, Symons SP, Huynh TJ, Marotta TR, Aviv RI, Bharatha A. First-Pass Contrast- Enhanced MR Angiography in Evaluation of Treated Spinal Arteriovenous Fistulas: Is Catheter Angiography Necessary? AJNR Am J Neuroradiol. Jan 2017;38(1):200-205. doi:10.3174/ajnr.A4971
3. Saindane AM, Boddu SR, Tong FC, Dehkharghani S, Dion JE. Contrast-enhanced time- resolved MRA for pre-angiographic evaluation of suspected spinal dural arterial venous fistulas. J Neurointerv Surg. Feb 2015;7(2):135-40. doi:10.1136/neurintsurg-2013-010981
4. Shin JH, Choi Y, Park B, et al. Diagnostic accuracy and efficiency of combined acquisition of low-dose time-resolved and single-phase high-resolution contrast-enhanced magnetic resonance angiography in a single session for pre-angiographic evaluation of spinal vascular disease. PLoS One. 2019;14(3):e0214289. doi:10.1371/journal.pone.0214289
5. National Institute of Neurological Disorders and Stroke. Arteriovenous Malformations and Other Vascular Lesions of the Central Nervous System Fact Sheet. National Institutes of Health (NIH). Updated July 25, 2022. Accessed January 29, 2023. https://www.ninds.nih.gov/Disorders/Patient-Caregiver-Education/Fact-Sheets/Arteriovenous- Malformation-Fact-Sheet
6. Vargas MI, Gariani J, Sztajzel R, et al. Spinal cord ischemia: practical imaging tips, pearls, and pitfalls. AJNR Am J Neuroradiol. May 2015;36(5):825-30. doi:10.3174/ajnr.A4118
7. American College of Radiology. ACR Appropriateness Criteria® Myelopathy. American College of Radiology (ACR). Updated 2020. Accessed January 29, 2023. https://acsearch.acr.org/docs/69484/Narrative/
8. Goldberg AL, Kershah SM. Advances in imaging of vertebral and spinal cord injury. J Spinal Cord Med. 2010;33(2):105-16. doi:10.1080/10790268.2010.11689685
9. Montalvo M, Bayer A, Azher I, Knopf L, Yaghi S. Spinal Cord Infarction Because of Spontaneous Vertebral Artery Dissection. Stroke. Nov 2018;49(11):e314-e317. doi:10.1161/strokeaha.118.022333
10. Vargas MI, Nguyen D, Viallon M, et al. Dynamic MR angiography (MRA) of spinal vascular diseases at 3T. Eur Radiol. Oct 2010;20(10):2491-5. doi:10.1007/s00330-010-1815-6
11. Backes WH, Nijenhuis RJ. Advances in spinal cord MR angiography. AJNR Am J Neuroradiol. Apr 2008;29(4):619-31. doi:10.3174/ajnr.A0910
12. Mordasini P, El-Koussy M, Schmidli J, et al. Preoperative mapping of arterial spinal supply using 3.0-T MR angiography with an intravasal contrast medium and high-spatial-resolution steady-state. Eur J Radiol. May 2012;81(5):979-84. doi:10.1016/j.ejrad.2011.02.025
13. American College of Radiology (ACR), American Society of Neuroradiology (ASNR), Society of Computed Body Tomography and Magnetic Resonance (SCBT-MR), Society for Skeletal Radiology (SSR). ACR–ASNR–SCBT-MR–SSR Practice Parameter for the Performance of Magnetic Resonance Imaging (MRI) of the Adult Spine. American College of Radiology. Updated 2018.

Coding Section

Procedure and diagnosis codes on Medical Policy documents are included only as a general reference tool for each policy. They may not be all-inclusive. 

This medical policy was developed through consideration of peer-reviewed medical literature generally recognized by the relevant medical community, U.S. FDA approval status, nationally accepted standards of medical practice and accepted standards of medical practice in this community, Blue Cross Blue Shield Association technology assessment program (TEC) and other nonaffiliated technology evaluation centers, reference to federal regulations, other plan medical policies, and accredited national guidelines.

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