How do you determine which spinal level to MRI for a suspected herniated disc?

From the Guidelines

To determine which spinal level to MRI for a suspected herniated disc, focus on the patient's clinical presentation, particularly their neurological symptoms and pain distribution, as the most recent and highest quality study from 2021 suggests that accurate diagnosis of disc disease can be provided by MRI 1. When evaluating a patient with suspected herniated disc, it is essential to begin with a thorough neurological examination to identify specific dermatomes, myotomes, and reflexes affected, as these correlate with particular spinal levels. For example, L4-L5 disc herniations typically cause weakness in foot dorsiflexion and pain radiating to the lateral leg, while C6-C7 herniations often present with weakness in the triceps and altered sensation in the middle finger. Some key points to consider when determining which spinal level to MRI include:

• Imaging should include the symptomatic region plus adjacent levels, such as the entire lumbar spine for lower back and leg symptoms or the cervical spine for neck and arm symptoms.
• When symptoms are unclear or suggest multiple levels, consider imaging a broader region.
• Electromyography (EMG) and nerve conduction studies can provide additional information about specific nerve root involvement before ordering an MRI.
• The MRI findings must correlate with clinical symptoms to guide treatment decisions effectively, as stated in the 2021 study 1.
• According to the American College of Radiology, patients presenting with subacute or chronic low back pain or radiculopathy who have failed 6 weeks of conservative therapy, and with physical examination signs of nerve root irritation, should be imaged if they are believed to be candidates for surgery or intervention or if diagnostic uncertainty remains 1. It is crucial to prioritize the patient's clinical presentation and correlate the MRI findings with their symptoms to ensure appropriate diagnosis and treatment, as recommended by the American College of Physicians and the American Pain Society in their 2007 guideline 1.

From the Research

Determining Spinal Level for MRI in Suspected Herniated Disc

To determine which spinal level to MRI for a suspected herniated disc, several factors and tests can be considered:

• The patient's symptoms, such as the location and radiation of pain, can provide clues about the affected spinal level 2.
• Physical examination tests, including the Straight Leg Raising (SLR) test and the Slump test, can be used to assess for nerve root compression and identify the level of herniation 3, 4.
• The SLR test has been found to have high sensitivity in detecting lumbar disc herniations, especially those leading to root compression that may require surgery 4.
• The Slump test, a variant of the SLR test, has been shown to be more sensitive than the SLR test in detecting lumbar disc herniations, but less specific 4.
• Combining the results of physical examination tests and medical history can increase the predictive value of these diagnostic tools 5.
• Imaging tests, such as MRI, are typically delayed until a patient is clearly a surgical candidate, and are used to confirm the diagnosis and identify the level of herniation 2, 6.

Common Spinal Levels Affected by Herniated Discs

• The majority of lumbar disc herniations occur at the L4-5 or L5-S1 levels, making these levels a common focus of physical examination and imaging studies 2.
• The physical examination should focus on abnormalities of the L5 and S1 nerve roots, as these are the most commonly affected nerve roots in lumbar disc herniations 2.

Importance of Accurate Diagnosis

• An accurate diagnosis is essential to prevent recurrences of low back pain and chronic spinal pain, and to guide management decisions 4, 5.
• Confirmatory tests, such as MRI, are necessary for a definitive diagnosis when making management decisions, especially when considering surgery 2, 6.