What MRI should I order for a patient with suspected cervical radiculopathy and brachial plexus pain?

MRI Ordering for Cervical Radiculopathy vs. Brachial Plexus Pain

When cervical radiculopathy and brachial plexopathy are both in your differential, start with MRI cervical spine without contrast, and if this is negative or inconclusive but clinical suspicion for plexopathy remains high, proceed to dedicated MRI brachial plexus with and without contrast. 1

Initial Imaging Strategy

Order MRI cervical spine without contrast first because radiculopathy is far more common than plexopathy, and cervical spine MRI is often performed before brachial plexus imaging due to the considerably higher prevalence of radiculopathy-related degenerative spine disease. 1 MRI cervical spine has become the preferred method to evaluate suspected nerve root impingement, with 88% accuracy in correctly predicting lesions in cervical radiculopathy. 1

Key Clinical Distinction Points

Before ordering imaging, clarify which diagnosis is more likely:

• Radiculopathy typically presents with: Pain following a single dermatome distribution, weakness in a single myotomal pattern, and sensory loss in one dermatome 2
• Plexopathy typically presents with: Pain crossing multiple dermatomes, weakness in regions innervated by multiple nerves from the affected plexus, and sensory loss across multiple nerve distributions 2

When to Add Dedicated Brachial Plexus MRI

Proceed to MRI brachial plexus with and without contrast if: 1, 3

• Cervical spine MRI is negative or shows only asymptomatic findings (occurs in 13-15% of radiculopathy cases and 45% show compression without clinical substrate) 4
• Clinical examination suggests plexus involvement (multiple nerve distributions affected) 2
• Symptoms don't match cervical spine MRI findings 1
• You suspect a mass, tumor, or extrinsic compression beyond the neural foramina 1, 3

Critical Technical Requirement

Standard cervical spine MRI protocols are inadequate for evaluating the brachial plexus. 1, 3 Cervical spine MRI does not evaluate the brachial plexus lateral to the neural foramina, which is why dedicated brachial plexus imaging requires different sequences including orthogonal views through the oblique planes of the plexus with T1, T2, fat-saturated T2 or STIR, and fat-saturated T1 postcontrast sequences. 1, 3

Why This Sequential Approach

The clinical diagnosis of plexopathy can be challenging because there is considerable overlap in clinical presentations between radiculopathy and plexopathy. 1 However, dedicated brachial plexus MRI provides:

• Superior diagnostic accuracy: Sensitivity 81%, specificity 96%, positive predictive value 87%, and overall accuracy 87% for plexopathy 5
• Additional information: Provides diagnostic information beyond clinical evaluation and electrodiagnostic studies in 45% of patients 1
• Better specificity: Complementing spine imaging with brachial plexus MRI improves diagnostic accuracy by increasing specificity from 69% to 96% 5

Contrast Considerations

• For cervical spine MRI: Contrast is usually not necessary for initial evaluation of radiculopathy 1
• For brachial plexus MRI: Use both with and without contrast, as this can detect and characterize tumors, inflammatory conditions, and masses that may be missed on non-contrast studies 1, 3

Common Pitfalls to Avoid

• Don't assume cervical spine MRI adequately evaluates the plexus - it only shows the nerve roots within and immediately adjacent to the neural foramina 1, 3
• Don't over-interpret asymptomatic findings - 45% of cervical radiculopathy patients show root compression on MRI without clinical substrate, and 65% of asymptomatic patients aged 50-59 have radiographic cervical spine degeneration 1, 4
• Don't order "MRI neck" or "MRI chest" for plexus evaluation - these lack the specialized sequences needed for proper plexus visualization 1, 3
• Recognize that peripheral nerve T2-weighted lesions can be caused by cervical radiculopathy - 79% of cervical radiculopathy cases show peripheral nerve lesions that can mimic inflammatory neuropathies 5

Alternative if MRI Contraindicated

If the patient cannot undergo MRI due to implanted devices, CT myelography cervical spine is the next best option for radiculopathy evaluation, though it cannot evaluate the plexus itself beyond the neural foramina. 1