What is the diagnostic approach to suspected cauda equina syndrome?

Diagnostic Approach to Cauda Equina Syndrome

Immediate MRI is essential for all suspected cases of cauda equina syndrome and should be performed at the district general hospital as part of triage. 1, 2

Red Flag Signs Requiring Immediate Action

• Bilateral radiculopathy (bilateral radicular pain and/or bilateral sensory disturbance or motor weakness) 1, 2
• New difficulties in micturition with preserved control (any new change in bladder function) 1, 2
• Subjective and/or objective loss of perineal sensation 1, 2
• Progressive neurological deficits in the legs 2

Diagnostic Algorithm

Initial Assessment

• Evaluate for red flag symptoms with high index of suspicion, as no single symptom or sign has high positive predictive value 1, 2
• Perform thorough neurological examination focusing on:
  • Lower extremity motor and sensory function 2, 3
  • Perineal and perianal sensation (saddle anesthesia) 4, 3
  • Rectal tone assessment 3
  • Bladder function assessment (including post-void residual measurement) 5

Imaging

• MRI without and with IV contrast is the gold standard with 96% sensitivity and 94% specificity for suspected cauda equina syndrome 1
• MRI should be performed emergently (within 1 hour of presentation) 4
• MRI cannot diagnose CES alone (which is a clinical diagnosis) but can identify significant compression of cauda equina nerve roots 1
• CT has limited utility with only 6% sensitivity for epidural abscess and should not be the primary imaging modality 1

Post-Imaging Management

• Emergency neurosurgical consultation for all cases with MRI-confirmed compression 2, 4
• Surgical decompression is recommended within 48 hours, preferably within 24 hours 6
• Better outcomes are associated with surgery within 12-72 hours of symptom onset 2

Classification of Cauda Equina Syndrome

• Suspected CES: Red flag symptoms without complete retention 2, 6
• Incomplete CES: Partial bladder dysfunction with sensory/motor deficits 2, 6
• Complete CES with retention: Late-stage with urinary retention (white flag symptom) 1, 2

Common Pitfalls to Avoid

• Waiting for complete urinary retention before referral (this is a late "white flag" sign indicating potentially irreversible damage) 1, 2
• Delaying MRI when cauda equina syndrome is suspected 2, 4
• Inadequate assessment of perineal sensation and anal tone 6
• Attributing early signs and symptoms to common postoperative findings in post-surgical patients 3
• Expecting all classic symptoms to be present (most patients do not present with all symptoms) 5

Expected Outcomes Based on Timing

• Patients treated at the suspected or incomplete stage typically achieve normal or socially normal bladder and bowel control 2
• Patients treated at the complete stage have variable recovery, with 48-93% showing some improvement 2
• High rates of negative MRI (67-86%) are expected and necessary to achieve the lowest false negative rate 1