Summary

Cauda Equina Syndrome (CES) is a rare but devastating surgical emergency caused by compression of the nerve roots below the Conus Medullaris (L1/L2). The hallmark is Saddle Anaesthesia and Bladder/Bowel Dysfunction. It is classified into Incomplete (CES-I), where sensation is altered but retention is not complete, and Retention (CES-R), characterised by painless urinary retention and overflow incontinence. CES-I is the surgical window of opportunity; decompression must occur before retention sets in to prevent permanent disability. The "48-hour rule" is the absolute upper limit; ideally, decompression should occur within 4 hours of diagnosis. [1,2,3]

Key Facts

• Level: L1/L2 is where the Spinal Cord ends (Conus). Below this, the roots float (Cauda Equina).
• Incomplete vs Retention:
  • CES-I (Urgent): Reduced saddle sensation, difficulty voiding, but can void.
  • CES-R (Emergency): Painless retention (>500ml), overflow incontinence. Prognosis is significantly worse.
• Painless Retention: The bladder is numb. A full bladder (1000ml) that is not painful is a catastrophic sign.

Clinical Pearls

"The White Flags": Bilateral Sciatica is a "White Flag". It heralds impending CES. Do not ignore it.

"Painless is BAD": If a patient with severe back pain suddenly becomes "comfortable" but hasn't peed for 8 hours, panic. They have lost visceral sensation.

"Digital Rectal Exam (DRE)": It tests S2-S4. You assess: 1. Sensation (Pinprick), 2. Tone (Anal pinch), 3. Reflex (Bulbocavernosus). Documenting "No DRE done" is medicolegal suicide.

1. Neurological Exam (Lower Limb)

• Power: Test L2-S1. Bilateral weakness is a red flag.
• Sensation: Test dermatomes.

2. Saddle Sensation (Crucial)

• Test with a neurotip (pinprick).
• "Does this feel sharp?" on the buttock vs the perineum.

3. Digital Rectal Exam (DRE)

• Mandatory.
• Assess: Tone (Resting/Squeeze) and Sensation.

4. Bladder Scan (PVR)

• Post Void Residual: Ask patient to void. Scan bladder.
• >200ml: High suspicion.
• >500ml: Diagnostic of Retention (CES-R).

                 SUSPECTED C.E.S.
               (Bilateral Sciatica + ?)
                        ↓
            BLADDER SCAN + NEURO EXAM
                        ↓
             IS THERE DYSFUNCTION?
             ┌──────────┴──────────┐
            NO                    YES
             ↓                     ↓
       URGENT MRI           EMERGENCY MRI
       (Within 24h)         (Walk patient to scanner)
                                   ↓
                           CONFIRMED COMPRESSION?
                                   ↓
                          EMERGENCY SURGERY
                        (Decompression <48h)

Principle

Decompression of the Cauda Equina.

1. Urgent Discectomy / Laminectomy

• Timing:
  • CES-I: IMMEDIATELY (Day or Night). Goal is to prevent progression to retention.
  • CES-R: ASAP (Next available list). Evidence suggests outcome is already guarded, but decompression <48h maximizes chance of recovery.
• Technique: Wide Laminectomy (removing the back of the vertebra) to give the nerves room. Removal of disc fragment.

Bladder Care

• Catheter (IDC) remains until mobile.
• Trial of Void (TWOC): If fail, teach Intermittent Self Catheterization (ISC). Bladder recovery can take 2 years.

Rehabilitation

• Intensive Physio for leg weakness.
• Psychological support (Sexual dysfunction is devastating).

Gleave & Macfarlane (2002) - The 48 Hour Rule

• Landmark paper.
• Patients decompressed within 48 hours had significantly better bladder recovery than those delayed >48h.
• Nuance: Recent evidence suggests CES-I should be decompressed within hours (Stat), whereas CES-R has a poorer prognosis regardless of timing, but <48h is still the target.

Todd (2017) - Documenting DRE

• Review of litigation. "Failure to perform or document a DRE" was a primary factor in 40% of successful claims against GPs/ED doctors.

What is this condition?

The bundle of nerves at the bottom of your spine (the horse's tail) is being crushed. These nerves control your legs, bladder, bowel, and sexual function.

Why is surgery urgent?

Nerves are like electrical cables; if you squeeze them too long, they die. Once they die, they don't grow back. We have a very small window (hours) to take the pressure off.

Will I recover fully?

If we caught it early (before the bladder stopped working), the chances are good. If the bladder had already stopped working, recovery is slow (months to years) and may not be complete. Nerves grow back at 1mm per day.

Q1: Differentiate between CES-I and CES-R. A: CES-I (Incomplete): Sensory changes (saddle), subjective urinary difficulty, but retention is not complete (can still void). This is the critical window for salvage. CES-R (Retention): Painless urinary retention with overflow incontinence. Nerves are already ischaemic/damaged. Prognosis is worse.

Q2: What is the pathognomonic sensory finding in CES? A: Saddle Anaesthesia (S2-S5 dermatomes).

Q3: Describe the Bulbocavernosus Reflex. A: Squeezing the glans penis (or clitoris) / tugging on the catheter should cause reflex contraction of the anal sphincter. Absence indicates a lesion at S2-S4 (Conus/Cauda level).

Q4: What is the medicolegal "danger zone" for MRI timing? A: Delays >4 hours from presentation to scan in a hospital setting are often deemed indefensible if the patient deteriorates.

(End of Topic)