Urgent MRI of the Entire Spine Without and With IV Contrast
This patient requires an emergent MRI of the entire spine (cervical, thoracic, and lumbar) without and with IV contrast as the first test to order. 1
Clinical Presentation Indicates Cauda Equina Syndrome with High Risk for Malignant Spinal Cord Compression
This patient presents with the classic triad of cauda equina syndrome:
- Unilateral leg weakness (left hip flexion and leg extension 3/5 strength) 1
- Decreased perineal sensation (saddle anesthesia) 1
- Reduced rectal sphincter tone with urinary retention (300 mL on bladder scan) 1
The history of prostate cancer treated 10 years ago is critical—prostate cancer metastasizes to the spine in 15-30% of cases through Batson's plexus, with a predilection for the lumbar spine. 2 Malignant spinal cord compression (MSCC) occurs in 4-8% of men with prostate cancer, and retrospective studies show occult spinal cord compression in up to 30% of men with metastatic disease. 1
Why MRI of the Entire Spine is Essential
The American College of Radiology designates MRI of the entire spine without and with IV contrast as the gold standard imaging modality for suspected spinal cord compression and states it should be performed emergently. 1
Key reasons for imaging the entire spine:
- Prostate cancer metastases occur at multiple levels—imaging only the symptomatic lumbar region misses occult compression sites above or below. 1
- Extensive bone metastatic disease is an independent predictive factor for MSCC at multiple levels. 1
- MRI is superior to CT for detecting early spinal cord compression, bone marrow infiltration, and epidural disease before plain radiographs become abnormal. 3, 4
Immediate Management While Awaiting Imaging
Administer high-dose corticosteroids immediately (typically dexamethasone 10 mg IV, then 4-6 mg every 6 hours) while awaiting imaging—this is standard practice for suspected MSCC even before imaging confirmation. 1
The rationale is that the degree of neurologic function at the time of treatment initiation is the strongest predictor of post-treatment neurologic outcome. 1 Patients who are ambulatory before treatment have a much higher chance of remaining ambulatory after treatment. 1
Why Not Other Imaging Modalities?
- Plain radiographs: Insensitive for early spinal cord compression and miss soft tissue involvement. 3
- CT spine: Limited soft-tissue characterization compared to MRI and cannot adequately visualize the spinal cord or early epidural disease. 5
- Bone scan: Useful for detecting osseous metastases but does not visualize spinal cord compression or soft tissue involvement. 5
Critical Pitfall to Avoid
Do not delay imaging to obtain a bone scan first—this patient has neurologic deficits indicating cord or cauda equina compression, which is a neurosurgical emergency. 1 Bone scans are appropriate for staging asymptomatic patients with elevated PSA, but this patient requires immediate evaluation of the spinal cord and nerve roots. 5, 6
Next Steps After MRI
If MRI confirms spinal cord compression or cauda equina syndrome: