• 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.

Purpose
Indications for performing Magnetic Resonance Angiography (MRA) or Magnetic Resonance Venography (MRV) of the head/brain.
NOTE: Authorization for MR Angiography covers both arterial and venous imaging. The term angiography refers to both arteriography and venography
 

INDICATIONS FOR BRAIN MR ANGIOGRAPHY/MR VENOGRAPHY
Evaluation of Suspected Intracranial Vascular Disease (1,2)
Brain MRI/MRA are not approvable simultaneously unless they meet the criteria described below in the indications for Brain MRI/Brain MRA combination studies section. If there is a combination request* for an overlapping body part, either requested at the same time or sequentially (within the past 3 months) the results of the prior study should be:

• Inconclusive or show a need for additional or follow up imaging evaluation OR
• The office notes should clearly document an indication why overlapping imaging is needed and how it will change management for the patient.

(*Unless approvable in the combination section as noted in the guidelines)

Aneurysm Screening

• Screening for intracranial aneurysm if two or more first-degree family members (parent, brother, sister, or child) with history of intracranial aneurysm ⁽¹⁾
  • Note: Repeat study is recommended every 5-7 years ⁽³⁾
• For one first degree relative with aneurysm, asymptomatic screening is not indicated

- would require a neurological sign or symptom supporting clinical concern for aneurysm. ⁽⁴⁾

• Screening for aneurysm in high-risk populations ^{(1,5,6,7,8,9,10)}:
  • KNOWN genetic syndromes (see Genetic Syndromes and Rare Diseases)
  • Bicuspid aortic valve
  • Known aortic diseases (aneurysm, coarctation, dissection)

Suspected Vascular Abnormalities

• Suspected vascular malformation (arteriovenous malformation (AVM) or dural arteriovenous fistula) in patient with previous or indeterminate imaging study ⁽²⁾
• Thunderclap headache with continued concern for underlying vascular abnormality (i.e., aneurysm or reversible cerebral vasoconstriction syndrome) after initial negative brain imaging. (11,12,13,14)
  • Note: Negative brain CT < 6 hours after headache onset excludes subarachnoid hemorrhage in neurologically intact patients ⁽¹³⁾. MRI lacks sensitivity in excluding subarachnoid hemorrhage less than 24 hours after headache onset. ^(11,15)
• Headache associated with exercise, exertion, Valsalva or sexual activity ⁽¹¹⁾
• Isolated third nerve palsy (oculomotor) with pupil involvement to evaluate for aneurysm ^(16,17)
• Horner’s syndrome, non-central (miosis, ptosis, and anhidrosis) ⁽¹⁸⁾
• Pulsatile tinnitus to identify a suspected arterial vascular etiology^(19,20)

Note: MRI is the study of choice for detecting cavernomas, developmental venous anomalies and capillary telangiectasia (see backgroundsection) ⁽²⁾

Cerebrovascular Disease
Ischemic

• Recent ischemic stroke or transient ischemic attack (See backgroundsection) ^(21,22)
  • Note: For remote strokes with no prior vascular imaging, imaging can be considered based on location/type of stroke and documented potential to change management
• Known or suspected vertebrobasilar insufficiency (VBI) in patients with symptoms such as dizziness, vertigo, headaches, diplopia, blindness, vomiting, ataxia, weakness in both sides of the body, or abnormal speech. ^{(23,24,25,26)}
• Suspected carotid or vertebral artery dissection; secondary to trauma or spontaneous due to weakness of vessel wall ^(27,28)

Hemorrhagic

• Known subarachnoid hemorrhage (SAH) – CTA is favored over MRA ^(1,2)
• Known cerebral intraparenchymal hemorrhage with concern for underlying vascular abnormality ^(2,22)

Venous – MRV*** (14,22)

• Suspected venous thrombosis (dural sinus thrombosis)
• Distinguishing benign intracranial hypertension (pseudotumor cerebri) from dural sinus thrombosis

Sickle cells disease (ischemic and/or hemorrhagic) (29)

• Neurological signs or symptoms in sickle cell disease
• Stroke risk in sickle cell patients (2 - 16 years of age) with a transcranial doppler velocity > 200

Vasculitis and Other Intracranial Vascular Disease

• Suspected secondary CNS vasculitis based on neurological signs or symptoms in the setting of an underlying systemic disease with abnormal inflammatory markers or autoimmune antibodies ⁽¹⁾
• Suspected primary CNS vasculitis based on neurological signs and symptoms with completed infectious/inflammatory lab work-up ^(1,30,31)
• Large vessel vasculitis (Giant cell or Takayasu arteritis) with suspected intracranial involvement (32,33,34,35,36)
• Suspected Moyamoya disease ^(2,37)
• Suspected reversible cerebral vasoconstriction syndrome ^(14,38)

Note: Vessel wall MRI (ordered as Brain MRI) can also be performed in the evaluation of vasculitides (39)

Evaluation of Known Intracranial Vascular Disease (1,2)

• Known intracranial aneurysm, treated aneurysm, or known vascular malformation (i.e., AVM or dural arteriovenous fistula)
• Known vertebrobasilar insufficiency with new or worsening signs or symptoms (VBI) (23,24,26)
• Follow-up of known carotid or vertebral artery dissection within 3-6 months for evaluation of recanalization and/or to guide anticoagulation treatment ^(40,41)
• Known vasculitis, reversible cerebral vasoconstriction syndrome or Moyamoya disease (2,31,42,43,44,45)

Pre-operative/procedural Evaluation

• Pre-operative evaluation for a planned surgery or procedure
• Refractory trigeminal neuralgia or hemifacial spasm when done for surgical evaluation ^(46,47)

Post-operative/procedural Evaluation (48,49)

• 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.

Further Evaluation of Indeterminate Findings
Unless follow up is otherwise specified within the guideline:

• For initial evaluation of an inconclusive finding on a prior imaging report (i.e., x-ray, ultrasound or CT) 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.)

Genetic Syndromes and Rare Diseases

• Fibromuscular dysplasia (FMD):^(50,51)
  • One-time vascular study from brain to pelvis
• Vascular Ehlers-Danlos syndrome:^(52,53)
  • At diagnosis and then every 18 months
  • More frequently if abnormalities are found
• Loeys-Dietz:⁽⁵⁴⁾
  • At diagnosis and then every two years
  • More frequently if abnormalities are found
• Spontaneous coronary arteries dissection (SCAD) ⁽⁵⁵⁾
  • One-time vascular study from brain to pelvis
• Fabry disease annual neurologic assessment with brain MRI/MRA every two to three years beginning at age 18 years ⁽⁵⁶⁾
• For other syndromes and rare diseases not otherwise addressed in the guideline, coverage is based on a case-by-case basis using societal guidance.

Combination Studies
Brain MRA and Neck MRA

• Symptomatic patients with an abnormal ultrasound of the neck or carotid duplex imaging (e.g., carotid stenosis ≥ 50%, technically limited study, aberrant direction of flow in the carotid or vertebral arteries) and patient is surgery or angioplasty candidate ^(62,65)
• Pulsatile tinnitus to identify a suspected arterial vascular etiology^(19,20)

Brain MRI and Brain MRA

• Recent ischemic stroke or transient ischemic attack (TIA) ^(21,22)
• Thunderclap headache with continued concern for underlying vascular abnormality (i.e., aneurysm or reversible cerebral vasoconstriction syndrome) after initial negative brain imaging (11,12,13,14)
  • Note: Negative brain CT < 6 hours after headache onset excludes subarachnoid hemorrhage in neurologically intact patients ⁽¹³⁾. MRI lacks sensitivity in excluding subarachnoid hemorrhage less than 24 hours after headache onset. ^(11,15)
• Acute, sudden onset of headache with personal history of a vascular abnormality or first-degree family history of aneurysm ^(1,14)
• Headache associated with exercise, exertion, Valsalva or sexual activity ⁽¹¹⁾
• Suspected venous thrombosis (dural sinus thrombosis) ⁽²²⁾– MRI/MRV**
• Neurological signs or symptoms in sickle cell patients ⁽²⁹⁾
• High stroke risk in sickle cell patients (2 - 16 years of age) with a transcranial doppler velocity > 200 ⁽²⁹⁾
• Known Moyamoya disease ^(2,37) or reversible cerebral vasoconstriction with any new or changing neurological signs or symptoms ^(14,38)
• Suspected secondary CNS vasculitis based on neurological signs or symptoms in the setting of an underlying systemic disease with abnormal inflammatory markers or autoimmune antibodies ⁽¹⁾
• Suspected primary CNS vasculitis based on neurological signs and symptoms with completed infectious/inflammatory lab work-up ^(1,30,31)
• Giant cell arteritis with suspected intracranial involvement
• Fabry disease annual neurologic assessment with brain MRI/MRA every two to three years beginning at age 18 years ⁽⁵⁶⁾

Brain MRI/Brain MRA/Neck MRA

• Recent ischemic stroke or transient ischemic attack (TIA) ^(21,22)
• Suspected carotid or vertebral artery dissection with focal or lateralizing neurological deficits
• Pulsatile tinnitus with concern for a suspected arterial vascular and/or intracranial etiology ^(19,20) (Brain MRI should include IAC)
• Giant cell arteritis with suspected intracranial and extracranial involvement
• Approved indications as noted above and being performed in a child under 8 years of age who will need anesthesia for the procedure and there is a suspicion of concurrent intracranial pathology ⁽⁶⁶⁾

Note: CTA and MRA are generally comparable noninvasive imaging alternatives each with their own advantages and disadvantages. Brain MRI can be combined with Brain CTA/Neck CTA.

Brain/Neck/Chest/Abdomen/Pelvis MRA

• For patients with fibromuscular dysplasia (FMD), a one-time vascular study from brain to pelvis ^(50,51)
• Vascular Ehlers-Danlos syndrome: At diagnosis and then every 18 months; more frequently if abnormalities are found ^(52,53)
• Loeys-Dietz: at diagnosis and then every two years, more frequently if abnormalities are found ⁽⁵⁴⁾
• For assessment in patients with spontaneous coronary artery dissection (SCAD), can be done at time of coronary angiography ⁽⁶⁷⁾

Rationale
Magnetic resonance angiography (MRA) or magnetic resonance venography (MRV) can be used as a first-line investigation of intracranial vascular disease. It is an alternative to invasive intra-catheter angiography that was once the mainstay for the investigation of intracranial vascular disease. MRA/MRV may use a contrast agent, gadolinium, which is non-iodine-based, for better visualization. It can be used in patients who have history of contrast allergy and who are at high risk of kidney failure. A single authorization covers both MRA and MRV.

MRA and Non-Aneurysmal Vascular Malformations
Non-aneurysmal vascular malformations can be divided in low flow vascular malformations and high flow vascular malformations. Low flow vascular malformations include dural venous anomalies (DVA), cavernomas, and capillary telangiectasias. High flow vascular malformations include AVM and dural arteriovenous fistulas (dAVF). For low flow malformations, MRI is the study of choice. There is limited medical literature to support vascular imagining (CTA or MRA). CTA plays a limited role in the assessment of cavernoma but may be used to demonstrate a DVA. MRA is not usually helpful in the assessment of cavernoma, capillary telangiectasia, and DVA. Vascular imaging is indicated in high flow vascular malformations. (1,2,68)

There is no evidence to support screening of first-degree relatives for AVMs (69). The risk of having an AVM may be higher than in the general population, but absolute risk is low.
 

Pulsatile tinnitus
Pulsatile tinnitus has many etiologies, and the choice of study should be based on accompanying signs and symptoms. For general screening MRI brain with IAC/MRA brain and neck is approvable. If IIIH is suspected (typically with headache and vision changes in a younger woman with a high BMI), MRI/MRV brain is indicated. If there is concern for vascular etiology, CTA or MRA brain/neck is indicated. If there is associated hearing loss and neurological signs/symptoms, MRI brain with IAC is indicated. If the temporal bone is suspected to be involved and/or retrotympanic lesion seen on otoscopy, CT temporal bone/IAC is indicated. If there is concurrent concern for boney and a vascular issue, CTA of the head and neck can be used to evaluate both.

MRA and Recent Stroke or Transient Ischemic Attack

• When revascularization therapy is not indicated or available in patients with an ischemic stroke or TIA, the focus of the work-up is on secondary prevention. Both stroke and TIA should have an evaluation for high-risk modifiable factors such as carotid stenosis atrial fibrillation as the cause of ischemic symptoms ⁽⁷⁰⁾. Diagnostic recommendations include neuroimaging evaluation as soon as possible, preferably with magnetic resonance imaging, including DWI; noninvasive imaging of the extracranial vessels should be performed, and noninvasive imaging of intracranial vessels is reasonable. ⁽⁷¹⁾
• Patients with a history of stroke and recent work-up with new signs or symptoms indicating progression or complications of the initial CVA should have repeat brain imaging as an initial study. Patients with remote or silent strokes discovered on imaging should be evaluated for high-risk modifiable risk factors based on the location and type of the presumed etiology of the brain injury.

MRA vs CTA for CVA
Preferred vascular imaging of the head and neck includes non-contrast head MRA and contrast-enhanced neck MRA. MRA may not be able to be performed in patients with claustrophobia, morbid obesity, or implanted device, but it can be useful in patients with renal failure or contrast allergies. In patients with high radiation exposure, MRA as an alternative should be considered. For acute stroke, CTA is preferred after CT (to rule of hemorrhage) and to look for thrombus/possible intervention that is time-sensitive. (2,22)

MRA and Intracerebral Hemorrhage (72)
MRA is useful as a screening tool for an underlying vascular abnormality in the evaluation of spontaneous intracerebral hemorrhage (ICH). Etiologies of spontaneous ICH include tumor, vascular malformation, aneurysm, hypertensive arteriopathy, cerebral amyloid angiopathy, venous thrombosis, vasculitis, RCVS, drug-induced vasospasm, venous sinus thrombosis, Moyamoya disease, anticoagulant use and hemorrhagic transformation of an ischemic infarct. History can help point to a specific etiology. Possible risk factors for the presence of underlying vascular abnormalities include age younger than 65, female, lobar or intraventricular location, and the absence of hypertension or impaired coagulation.
 

MRV and Central Venous Thrombosis **
MR Venogram is indicated for the evaluation of a central venous thrombosis/dural sinus thrombosis. The most frequent presentations are isolated headache, intracranial hypertension syndrome (headache, nausea/vomiting, transient visual obscurations, pulsatile tinnitus, CN VI palsy, papilledema) (73), seizures, focal neurological deficits, and encephalopathy. Risk factors are hypercoagulable states inducing genetic prothrombotic conditions, antiphospholipid syndrome and other acquired prothrombotic diseases (such as cancer), oral contraceptives, pregnancy, puerperium (6 weeks postpartum), infections, and trauma. COVID-19 infection is associated with hypercoagulability, a thromboinflammatory response, and an increased incidence of venous thromboembolic events (VTE) (74,75). Since venous thrombosis can cause SAH, infarctions, and hemorrhage, parenchymal imaging with MRI/CT is also appropriate (76,77,78).

MRA and Dissection
Craniocervical dissections can be spontaneous or traumatic. Patients with blunt head or neck trauma who meet Denver Screening criteria should be assessed for cerebrovascular injury (although about 20% will not meet criteria). The criteria include focal or lateralizing neurological deficits (not explained by head CT); infarct on head CT; face, basilar skull, or cervical spine fractures; cervical hematomas that are not expanding; Glasgow coma score less than 8 without CT findings; massive epistaxis; cervical bruit or thrill. (27,79,80)

Spontaneous dissection presents with headache, neck pain with neurological signs or symptoms. There is often minor trauma or precipitating factor (i.e., exercise, neck manipulation). Dissection is thought to occur due to weakness of the vessel wall, and there may be an underlying connective tissue disorder. Dissection of the extracranial vessels can extend intracranially and/or lead to thrombus which can migrate into the intracranial circulation, causing ischemia. Therefore, MRA of the head and neck is warranted. (28,81)

Moyamoya Disease
Family members of Moyamoya Disease (MMD) patients may also have MMD, but not have any obvious symptoms. Routine screening should be implemented for all family members of MMD patients. TCD may be the preferred choice for screening because it is inexpensive and safe and as a high diagnostic agreement with MRA.

Combination MRI/MRA of the Brain
This is one of the most misused combination studies and other than what is indicated above these examinations should be ordered in sequence, not together. Vascular abnormalities can be visualized on the brain MRI.

Patients presenting with a new migraine with aura (especially an atypical or complex aura) can mimic a transient ischemic attack or an acute stroke. If there is a new neurologic deficit, imaging should be guided by concern for cerebrovascular disease, not that the patient has a headache. (14)

Contraindications 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 weight limit/dimensions of MRI machine.

References