Table 1.

Recommendations from The American Heart Association/American Stroke Association guideline for vascular imaging of vertebral artery disease[21]

Size of treatment effect	Indications	Recommended imaging study	Level of evidence (A,B,C1)
Class 1 (benefit>>>risk)
1	-With symptoms referable to posterior circulation and subclavian steal syndrome	Noninvasive imaging	C
2	-With asymptomatic bilateral carotid occlusions or-Unilateral carotid artery occlusion and incomplete circle of Willis	Noninvasive imaging	C
3	-With symptoms of posterior cerebral ischemia or -With symptoms of cerebellar ischemia	Noninvasive imaging (MRA or CTA rather than Doppler US)	C
Class 2a (benefit>>risk)
1	-With symptoms of posterior cerebral ischemia or -With symptoms of cerebellar ischemia	Serial noninvasive imaging	C
2	-Revascularization candidates with symptoms of posterior cerebral ischemia or -Revascularization candidates with symptoms of cerebellar ischemia	-Noninvasive imaging -DSA (if noninvasive imaging fails)	C
3	-Patients undergone vertebral artery revascularization	-Serial noninvasive imaging	C

¹Level of evidence C indicates that very limited populations were evaluated and it depends on consensus opinion of experts, case studies or standard of care. MRA: Magnetic resonance angiography; CTA: Computed tomography angiography; Doppler US: Doppler ultrasonography; DSA: Digital subtraction angiography.