Urgent MRI and Immediate Surgical Consultation Required
This patient has cauda equina syndrome (CES) until proven otherwise—obtain urgent MRI lumbar spine without contrast within 1 hour and arrange immediate neurosurgical consultation. 1, 2, 3
Critical Red Flags Present
This patient demonstrates the classic triad of CES:
- Difficulty with urination (bladder dysfunction—the most sensitive early finding) 1, 2
- Perineal numbness (saddle anesthesia) 1, 2, 3
- Unilateral radicular pain (left leg pain suggesting nerve root compression) 1, 2
The combination of these symptoms following trauma with normal plain radiographs is highly suspicious for acute disc herniation causing cauda equina compression. 4, 3
Immediate Diagnostic Approach
Urgent MRI Protocol
- MRI lumbar spine without IV contrast is the imaging study of choice and should be obtained within 1 hour of presentation to the emergency department 1, 2, 3
- MRI accurately depicts soft-tissue pathology, assesses vertebral marrow, and evaluates spinal canal patency—critical for identifying disc herniation compressing the cauda equina 1, 2
- Normal X-rays do not exclude CES; most cases result from soft tissue pathology (disc herniation in 45% of cases) that is invisible on plain films 4, 5
If MRI Unavailable or Significantly Delayed
- CT myelography is an acceptable alternative if MRI cannot be obtained urgently, though MRI remains strongly preferred 1, 6
- Do not delay evaluation beyond 1-2 hours waiting for MRI if it requires transfer to another facility—arrange immediate transfer 3
Surgical Timing is Critical
Emergency decompressive surgery within 48 hours of symptom onset provides the best chance for neurologic recovery. 4, 3, 7
- Of patients who underwent surgery within 48 hours, 70% had no postoperative incontinence 7
- All patients with persistent incontinence in one series had surgery delayed beyond 48 hours 7
- Any delay in diagnosis and treatment leads to poor prognosis with potentially permanent bladder, bowel, and sexual dysfunction 4, 3
Clinical Assessment Details to Document
Before imaging, rapidly assess and document:
- Bladder function: Ask specifically about urinary retention (inability to void), overflow incontinence, or loss of urge sensation 1, 2, 3
- Saddle anesthesia: Test sensation in the perineum, perianal area, and inner thighs 1, 2
- Motor examination: Test bilateral hip flexion, knee extension/flexion, ankle dorsiflexion/plantarflexion, and great toe extension 2
- Rectal examination: Assess anal sphincter tone and voluntary contraction 3, 5
- Reflexes: Check bilateral patellar and Achilles reflexes 2
Common Pitfalls to Avoid
- Do not wait for "complete" CES (bilateral sciatica, complete saddle anesthesia, frank incontinence)—early/incomplete CES with urinary difficulties and perineal numbness warrants the same urgent approach 3, 5
- Do not be falsely reassured by normal X-rays—disc herniations causing CES are soft tissue lesions not visible on plain radiographs 4, 5
- Do not delay imaging to complete a trial of conservative management—the presence of bladder dysfunction and saddle anesthesia are absolute indications for immediate imaging regardless of symptom duration 1, 2
- Do not order MRI "outpatient" or "within a few days"—this is a surgical emergency requiring imaging within 1 hour 3
Most Likely Diagnosis
L4-L5 or L5-S1 disc herniation causing cauda equina compression (these levels account for >85% of CES cases from disc herniation). 7, 5