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 Arteriovenous Malformations (AVMs) — Spinal cord arteriovenous malformations are comprised of snarled tangles of arteries and veins which affect the spinal cord. They are fed by spinal cord arteries and drained by spinal cord veins. 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 defines the vascular malformation and may assist in determining treatment.

Spinal MR Angiography/MR Venography
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% (Backes, 2008). 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 (Backes, 2008). MRI has the advantage over CT of being able to detect areas of ischemia through the use of diffusion weighted imaging. Mathur et al. showed a 100% sensitivity in detecting recurrent spinal arteriovenous fistulas post treatment.

Spinal Arteriovenous Malformations (AVMs) — Spinal cord arteriovenous malformations are comprised of snarled tangles of arteries and veins which affect the spinal cord. They are fed by spinal cord arteries and drained by spinal cord veins. 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 defines the vascular malformation and may assist in determining treatment (NIH, 2015).

Spinal Arteries/Veins (Vargas, 2015)
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 artery of Adamkiewicz. 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. 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 (Vargas, 2015).

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) (Amarouche, 2015; Mathur, 2017; NINDS, 2019; Shine, 2019).
• Myelopathy when the suspected etiology is compromise of blood flow or drainage to the spinal cord 9ACR, 2015; Vargas, 2015).
• 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.(ACR, 2015; Vargas, 2015).
• 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) (Goldberg, 2010; Montalvo, 2018).
• 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) (Backes, 2008; Mordasini, 2011; Vargas, 2010).
• Myelopathy when the suspected etiology is compromise of blood flow or drainage to the spinal cord (ACR, 2015; Vargas, 2015).
• 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 (Mathur, 2017).

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, et al. Time-resolved contrast-enhanced MR Angiography of spinal vascular malformations. AJNR Am J Neuroradiol. 2015 Feb; 36(2):417-422.
2. American College of Radiology (ACR). ACR Appropriateness Criteria®. Myelopathy. http://www.acr.org/Quality-Safety/Appropriateness-Criteria/Diagnostic. Published 2015.
3. Backes WH, Nijenhuis RJ. Advances in spinal cord MR angiography. AJNR Am J Neuroradiol. 2008 Apr;; 29(4):619-631. doi: https://doi.org/10.3174/ajnr.A0910. http://www.ajnr.org/content/29/4/619. Retrieved March 16, 2018.
4. Goldberg AL, Kershah SM. Advances in imaging of vertebral and spinal cord injury. J Spinal Cord Med. 2010; 33(2):105–116. doi:10.1080/10790268.2010.11689685.
5. Mathur S, Symons SP, Huynh TJ, et al. First-pass contrast-enhanced MR angiography in evaluation of treated spinal arteriovenous fistulas: Is catheter angiography necessary? AJNR Am J Neuroradiol. January 2017; 38(1):200-205; doi: https://doi.org/10.3174/ajnr.A4971. http://www.ajnr.org/content/38/1/200. Retrieved March 27, 2018.
6. Montalvo M, Bayer A, Azher I, et al. Spinal cord infarction because of spontaneous vertebral artery dissection. Stroke. 2018 Nov; 49(11):, e314-e317. https://doi.org/10.1161/STROKEAHA.118.022333.
7. 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. 2012 May; 81(5):979-84. doi: 10.1016/j.ejrad.2011.02.025. Epub 2011 Mar 4.
8. National Institute of Neurological Disorders and Stroke (NINDS), National Institutes of Health (NIH). Arteriovenous Malformations and other Vascular Lesions of the Central Nervous System: Fact Sheet. Bethesda, Maryland: NIH Publication No. 04-4854 Revised 2019.
9. 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 Mar 28; 14(3):e0214289.
10. 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):825-830. doi: https://doi.org/10.3174/ajnr.A4118. http://www.ajnr.org/content/36/5/825. Retrieved March 27, 2018.
11. Vargas, MI, Nguyen, D, Viallon, M, et al. Dynamic MR angiography (MRA) of spinal vascular diseases at 3T. Eur Radiol. 2010; 20,: 2491–2495. https://doi.org/10.1007/s00330-010-1815-6.

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 non-affiliated technology evaluation centers, reference to federal regulations, other plan medical policies, and accredited national guidelines.

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