Should MRI or CT with contrast be used to evaluate the vertebral artery before C1/2 and C0/1 injections?

From the Guidelines

MRI with contrast is the preferred imaging modality to evaluate the vertebral artery before C1/2 and C0/1 injections.

Key Points

• MRA allows for evaluation of the course and luminal caliber of the arteries, and can detect luminal filling defects, which may include thrombus, embolus, atherosclerotic plaque, dissection flap, or vascular web 1.
• The sensitivity, specificity, and accuracy of MRA were shown to be as high as 97%, 98%, and 93%, respectively, in evaluating vertebral artery origin stenosis 1.
• CTA has the highest reported sensitivity (100%) in detecting vertebral artery dissection, but MRA is still a valuable tool, especially when combined with nonluminal vessel wall imaging sequences 1.
• The use of CT with contrast may be appropriate in certain situations, but it is not the preferred initial imaging modality due to radiation concerns and lower sensitivity for certain types of lesions 1.

Imaging Recommendations

• MRA head and neck with IV contrast is usually appropriate for evaluating vertebral artery disease, with a rating of 6 or 8 depending on the specific clinical scenario 1.
• CTA head and neck with IV contrast may be appropriate in certain situations, but it is not the preferred initial imaging modality due to radiation concerns and lower sensitivity for certain types of lesions 1.

From the Research

Evaluation of Vertebral Artery before C1/2 and C0/1 Injections

To determine whether MRI or CT with contrast should be used to evaluate the vertebral artery before C1/2 and C0/1 injections, several factors must be considered, including the sensitivity and specificity of each imaging modality for detecting vertebral artery stenosis or anomalies.

Sensitivity and Specificity of Imaging Modalities

• Contrast-enhanced MR angiography has been shown to have the highest sensitivity and specificity for detecting vertebral artery stenosis, with sensitivity and specificity values of 0.83 and 0.91, respectively 2.
• CT angiography has good sensitivity and excellent specificity, with values of 0.68 and 0.92, respectively 2.
• MRI and nonenhanced CT have been found to have lower sensitivity for detecting high-risk vertebral artery anatomy, with sensitivity values of 0.31 and 0.37, respectively 3.
• The combination of MRI and nonenhanced CT has been shown to increase sensitivity to 0.50, with a minimal decrease in specificity 3.

Anomalies of the Vertebral Artery

• Anomalous courses of the vertebral artery, such as the C2 segmental type, can be detected using MRI and CT 4.
• MRI and MR angiography can also be used to diagnose vertebral artery dissection, with intramural dissecting hematoma appearing as crescentic or rounded high signal on T1-weighted images 5.

Comparison of MRI and CT

• MRI and contrast CT have been found to be comparable in their abilities to demonstrate spinal stenosis, with 96.6% agreement between the two modalities 6.
• MRI is more sensitive than CT in demonstrating disc degeneration, with detection rates of 74 and 27 segments, respectively 6.

Considerations for C1/2 and C0/1 Injections

• The choice of imaging modality for evaluating the vertebral artery before C1/2 and C0/1 injections should be based on the specific clinical scenario and the availability of imaging modalities.
• Contrast-enhanced MR angiography may be the preferred modality for detecting vertebral artery stenosis, while CT angiography may be preferred for evaluating high-risk vertebral artery anatomy.
• The combination of MRI and nonenhanced CT may be useful for increasing sensitivity and specificity in detecting vertebral artery anomalies.