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 Venography¹⁰ — Typically, contrast-enhanced 3D time of flight techniques and contrast-enhanced CT angiography (CTA) have been used for evaluation of the spinal arteries, veins, and related pathology as a non-invasive alternative to the gold standard catheter angiography. Magnetic resonance angiography is well suited to patients who cannot receive iodinated contrast. 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.⁸ MRI has the advantage over CT of detecting areas of ischemia via diffusion weighted imaging as is very sensitive in detecting recurrent spinal arteriovenous fistulas post-treatment.¹

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.¹¹

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.

Contraindication and Preferred Studies
Contraindications and reasons why a CT/CTA cannot be performed may include: impaired renal function, significant allergy to IV contrast, pregnancy (depending on trimester)

Contraindications and reasons why an MRI/MRA cannot be performed may include: impaired renal function, claustrophobia, non-MRI compatible devices (such as non- compatible defibrillator or pacemaker), metallic fragments in a high-risk location, patient exceeds wight limit/dimensions of MRI machine.

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)

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. Mathur S, Symons S, Huynh T, Marotta T, Aviv R. First-Pass Contrast-Enhanced MR Angiography in Evaluation of Treated Spinal Arteriovenous Fistulas: Is Catheter Angiography Necessary? AJNR Am J Neuroradiol. 2017; 38: 200-205. 10.3174/ajnr.A4971.
2. Mathur S, Symons S, Huynh T, Muthusami P, Montanera W. First-Pass Contrast-Enhanced MRA for Pretherapeutic Diagnosis of Spinal Epidural Arteriovenous Fistulas with Intradural Venous Reflux. AJNR. American journal of neuroradiology. 2017; 38: 195-199. 10.3174/ajnr.A5008.
3. Shin J, Choi Y, Park B, Shin N, Jang J 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: e0214289. 10.1371/journal.pone.0214289.
4. Wójtowicz K, Przepiorka L, Maj E, Kujawski S, Marchel A. Usefulness of time-resolved MR angiography in spinal dural arteriovenous fistula (SDAVF)-a systematic review and meta-analysis. Neurosurgical review. 2023; 47: 9. 10.1007/s10143-023-02242-7.
5. Agarwal V, Shah L, Parsons M, Boulter D, Cassidy R et al. ACR Appropriateness Criteria® Myelopathy: 2021 Update. Journal of the American College of Radiology. 2021; 18: S73 - S82. 10.1016/j.jacr.2021.01.020.
6. Vargas M, Gariani J, Sztajzel R, Barnaure-Nachbar I, Delattre B et al. Spinal cord ischemia: practical imaging tips, pearls, and pitfalls. AJNR Am J Neuroradiol. 2015; 36: 825-30. 10.3174/ajnr.A4118.
7. Montalvo M, Bayer A, Azher I, Knopf L, Yaghi S. Spinal Cord Infarction Because of Spontaneous Vertebral Artery Dissection. Stroke. 2018; 49: e314-e317. 10.1161/strokeaha.118.022333.
8. Backes W, Nijenhuis R. Advances in spinal cord MR angiography. AJNR Am J Neuroradiol. 2008; 29: 619-31. 10.3174/ajnr.A0910.
9. Mordasini P, El-Koussy M, Schmidli J, Bonel H, Ith M 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; 81: 979-84. 10.1016/j.ejrad.2011.02.025.
10. 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–SABI–SSR PRACTICE PARAMETER FOR THE PERFORMANCE OF MAGNETIC RESONANCE IMAGING (MRI) OF THE ADULT SPINE. American College of Radiology. 2023; Accessed March 5, 2024: https://www.acr.org/-/media/ACR/Files/Practice-Parameters/MR- Adult-Spine.pdf.
11. National Institute of Neurological Disorders and Stroke. Arteriovenous Malformations and Other Vascular Lesions of the Central Nervous System Fact Sheet. 2022; 2023:

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

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