What is the most appropriate next step for a patient with severe low back pain, radiating pain from the right buttock to the foot, intermittent burning and tingling, and a positive straight leg raise test, who has not responded to over-the-counter (OTC) lidocaine?

MRI of the Lumbar Spine is the Most Appropriate Next Step

This patient requires MRI of the lumbar spine because the clinical presentation—severe radiating pain with positive straight leg raise test—strongly suggests lumbar disc herniation with radiculopathy, which warrants imaging to guide potential surgical or interventional treatment decisions. 1, 2

Clinical Reasoning

This patient presents with classic signs of lumbar radiculopathy, not simple nonspecific low back pain:

• Radiating pain from buttock to foot in a dermatomal distribution indicates nerve root compression 2
• Positive straight leg raise test has 91% sensitivity for herniated disc 1
• Pain worsening with cough suggests increased intraspinal pressure affecting a compressed nerve root 2
• Burning and tingling are neuropathic pain characteristics consistent with radiculopathy 3

Why MRI is Indicated Now

MRI (preferred) or CT should be ordered in patients with persistent pain and signs or symptoms of radiculopathy, specifically when the patient is a potential candidate for surgery or epidural steroid injection. 2 This patient meets these criteria because:

• The severity of symptoms ("severe" pain) and functional impairment from buttock-to-foot radiation suggests significant nerve compression 1
• Positive straight leg raise test objectively confirms radiculopathy 1
• Failed conservative management (OTC lidocaine) indicates this is not self-limiting 2

The American College of Radiology guidelines specify that imaging is appropriate for patients with radiculopathy who have undergone 4-6 weeks of conservative management with little improvement, but also for those presenting with severe symptoms or significant neurological findings at initial presentation. 1

Why Other Options Are Inappropriate

Trial of ibuprofen alone delays definitive diagnosis in a patient with clear radiculopathy who needs imaging to determine if surgical intervention is warranted. 2 While NSAIDs are reasonable for pain management, they should not replace diagnostic imaging in this clinical scenario. 2

Contrast-enhanced CT is inferior to MRI for evaluating disc herniation and nerve root compression, and contrast is unnecessary for diagnosing mechanical radiculopathy. 2 CT is reserved for patients who cannot undergo MRI. 1

Pregabalin addresses neuropathic pain symptoms but does not establish the underlying diagnosis. 3 Starting neuropathic pain medications without imaging in a surgical candidate delays appropriate treatment and may mask progressive neurological deterioration. 2

Specialist referral without imaging is premature because the specialist will require MRI before making treatment recommendations anyway. 2 Obtaining MRI first expedites definitive care.

Common Pitfalls to Avoid

• Do not assume all low back pain requires conservative management first. The presence of radiculopathy with positive objective findings (straight leg raise) changes the management algorithm. 1, 2
• Do not wait the full 6-8 weeks for imaging when symptoms are severe or there are clear signs of nerve root compression. 1, 2
• Do not confuse nonspecific low back pain with radiculopathy. This patient has radicular symptoms requiring different evaluation. 2

Concurrent Management

While arranging MRI, initiate NSAIDs for pain control and advise the patient to remain active within pain tolerance. 2 However, the primary action is obtaining MRI to guide definitive treatment, as the majority of disc herniations improve within 4 weeks with conservative management, but surgical candidates need early identification. 2