Assessment and Management of Suspected Cauda Equina Syndrome
Any patient with bilateral leg symptoms (pain, numbness, or weakness) combined with new bladder changes or perineal sensory disturbance requires immediate emergency MRI and neurosurgical consultation—do not wait for urinary retention, as this represents irreversible damage. 1
Critical Red Flag Symptoms Requiring Immediate Action
The following symptoms demand emergency MRI within 1 hour of presentation 2:
- Bilateral radiculopathy (bilateral leg pain radiating below the knee, bilateral sensory disturbance, or bilateral motor weakness)—this is the earliest warning sign with 90% sensitivity for progression to urinary retention 1, 3
- Any new bladder symptoms with preserved control (hesitancy, frequency, incomplete emptying)—not just retention 1
- Subjective or objective perineal sensory changes in the "saddle" distribution—even if subtle 1, 3
- Progressive neurological deficits in both lower extremities 1
White Flag Symptoms Indicating Late-Stage Disease
These findings represent established, often irreversible damage 1:
- Painless urinary retention (90% sensitivity for established CES) 1
- Fecal incontinence 1
- Complete saddle anesthesia rather than partial sensory loss 1
- Patulous anus 1
Physical Examination Protocol
Perform the following focused examination 3:
- Perineal sensation testing—though subjective and easily missed, especially subtle impairment 1
- Digital rectal examination for voluntary anal tone—note that this has low interobserver reliability among inexperienced clinicians 1, 4
- Bulbocavernosus reflex testing 3
- Bilateral lower extremity motor and sensory examination 1
A combination of normal bulbocavernosus reflex, normal voluntary rectal tone, and intact perianal sensation can effectively rule out CES 1, but any abnormal findings mandate immediate MRI 1.
Diagnostic Imaging Algorithm
- MRI without and with IV contrast is the gold standard with 96% sensitivity and 94% specificity 1
- CT scan is inadequate—it has only 6% sensitivity for epidural abscess and neural compression and cannot visualize nerve root compression necessary for surgical decision-making 1
- Do not rely on CT findings alone to rule out CES, as significant neural compression can be missed 1
- MRI should be performed within 1 hour of presentation to the emergency department 2
Management Based on Clinical Stage
Incomplete CES (CESI)—bladder symptoms present but no retention:
- Emergency surgical decompression is indicated 1
- Patients treated at this stage typically achieve normal or socially normal bladder and bowel control 1, 5
- Do not catheterize before determining retention status, as this obscures whether the patient has CESI versus complete CES with retention (CESR) 3
Complete CES with retention (CESR):
- Urgent surgery within 12 hours is recommended 3
- Better outcomes occur with surgery within 12-72 hours of symptom onset compared to further delayed surgery 1, 5
- Variable recovery with 48-93% showing some improvement 1
- Recovery more likely if some perineal sensation preserved preoperatively 5, 3
Critical Pitfalls to Avoid
- Never wait for complete urinary retention before referral—this is a late sign indicating irreversible damage 1, 3
- Never dismiss bilateral leg symptoms as "just sciatica"—bilateral radiculopathy is the earliest red flag 3
- Never delay MRI when CES is suspected, even if clinical findings are subtle 3
- Never use steroids—they are not indicated in emergency CES management 1
- Recognize that symptoms typically develop gradually over weeks to months, which can lead to misattribution to benign causes 1
Expected Diagnostic Yield
Accept that MRI confirmation rates are typically only 14-33%, with emergency surgery rates of only 4-7% 1. A high true negative rate from MRI is necessary to achieve the lowest false negative rate based on clinical assessment 1. This low positive predictive value is acceptable and necessary given the catastrophic consequences of missed diagnosis 1.