What type of Magnetic Resonance Imaging (MRI) is indicated for foot drop after lumbar surgery?

From the Guidelines

For foot drop after lumbar surgery, an MRI of the lumbar spine with and without IV contrast is the most appropriate imaging study. This recommendation is based on the most recent and highest quality study available, which suggests that MRI lumbar spine without and with IV contrast is useful in distinguishing recurrent or residual disc herniations from scar, evaluating nerve root compression or arachnoiditis, and identifying the extent of infection in patients with new or progressive symptoms and previous lumbar surgery 1, 2.

The MRI should include T1 and T2-weighted sequences with axial and sagittal views to evaluate for potential causes such as recurrent disc herniation, epidural fibrosis, hematoma, or hardware complications that might be compressing the nerve roots (particularly L4-L5 or L5-S1 that supply the foot dorsiflexors). The use of contrast (gadolinium) is essential to help differentiate between scar tissue and recurrent disc herniation 2.

Some key points to consider when ordering an MRI for foot drop after lumbar surgery include:

• The importance of prompt imaging after the onset of symptoms to improve the chances of recovery
• The potential need for additional imaging studies, such as an MRI of the affected leg, to rule out peripheral nerve compression
• The usefulness of electromyography (EMG) and nerve conduction studies to assess the function of the nerves and muscles
• The role of CT myelography in assessing the patency of the spinal canal/thecal sac and of the subarticular recesses and neural foramen, particularly in patients with significant artifact from metallic surgical hardware on MRI 1

Overall, the goal of imaging in foot drop after lumbar surgery is to identify the underlying cause of the condition and guide appropriate management to improve morbidity, mortality, and quality of life outcomes. An MRI of the lumbar spine with and without IV contrast is the best initial imaging study to achieve this goal.

From the Research

Magnetic Resonance Imaging (MRI) for Foot Drop after Lumbar Surgery

• The type of MRI indicated for foot drop after lumbar surgery is not explicitly stated in the provided studies.
• However, the studies suggest that MRI is a crucial diagnostic tool for identifying the underlying cause of foot drop, such as lumbar disc herniation 3, 4, 5.
• For example, a study published in the British Journal of Neurosurgery 3 used urgent MRI to reveal an L4-L5 centrally located lumbar disc herniation with bilateral compression of the L5 nerve roots and the cauda equina.
• Another study published in the Journal of Spinal Disorders & Techniques 5 found that preoperative MRI was useful in diagnosing herniated nucleus pulposus and/or lumbar spinal stenosis, which can cause foot drop.

Diagnosis and Treatment of Foot Drop

• Foot drop can be caused by various factors, including lumbar disc herniation, nerve injury, and compartment syndromes 6.
• Treatment options for foot drop include ankle-foot orthoses, neurolysis, nerve repair, and tendon transfers 6, 7.
• A study published in the Journal of Clinical Neuroscience 7 found that soleus nerve transfer to deep peroneal nerve can be an effective treatment for foot drop caused by injury to the lumbar root or peroneal nerve.