Cauda Equina Syndrome

Cauda equina syndrome is compression of the lumbosacral nerve roots below the conus medullaris producing variable dysfunction of:

• Bladder
• Bowel
• Saddle sensation
• Sexual function
• Lower limb motor and sensory pathways

The commonest cause is a large central lumbar disc prolapse, but other causes include:

• Lumbar spinal stenosis
• Tumour
• Epidural abscess
• Epidural haematoma
• Trauma
• Postoperative haematoma
• Severe spondylolisthesis
• Inflammatory disease

CES is a spinal surgical emergency because prolonged compression can produce permanent bladder, bowel, sexual and motor disability.

Practical clinical classification

CES suspected

Red flag symptoms without objective major sphincter dysfunction.

Incomplete CES, CESI

Neurogenic urinary dysfunction is present but voluntary bladder emptying remains possible.

Features can include:

• Altered urinary sensation
• Loss of desire to void
• Poor stream
• Need to strain
• Saddle sensory change

CES with retention, CESR

The patient has painless urinary retention with overflow or loss of effective voluntary bladder control.

CESR generally has a poorer neurological recovery than CESI.

Do not wait for complete urinary retention before obtaining emergency imaging.

High value red flags are:

• Bilateral sciatica
• New saddle or perineal numbness
• New urinary difficulty
• Reduced awareness of bladder filling
• Poor urinary stream
• Urinary retention
• New faecal incontinence
• Reduced anal tone
• New sexual dysfunction
• Bilateral or progressive leg weakness

A patient can have CES without every classical feature.

Examination

Document:

• Hip, knee and ankle motor power
• Great toe extension
• Dermatomal sensation
• Saddle sensation
• Lower limb reflexes
• Anal tone
• Voluntary anal contraction where appropriate
• Bladder function

Do not overrely on digital rectal examination. Normal anal tone does not reliably exclude CES.

Bladder scan

Measure post void residual where available.

A PVR greater than approximately 200 mL increases concern for neurogenic bladder dysfunction.

However, a low PVR does not safely exclude incomplete CES when saddle symptoms or neurological deficits are present.

Emergency MRI lumbar spine: diagnostic investigation of choice.

When clinical suspicion is moderate or high, obtain MRI urgently rather than observing for progression.

Service standards support MRI in the next available emergency slot, aiming within approximately 4 hours of request for suspected acute CES.

If MRI is contraindicated or impossible:

• CT myelography can demonstrate compressive pathology

but it is invasive and requires specialist availability.

Do not delay emergency spinal referral while waiting for routine outpatient imaging.

Immediate management

Keep the patient:

• Nil orally if urgent surgery is likely
• Adequately analgesed
• Under serial neurological observation

If urinary retention exists:

Insert a urinary catheter and document the drained volume.

Catheterisation treats retention but does not treat the nerve compression.

Disc related CES

Once MRI confirms a surgically remediable disc prolapse producing cauda equina compression, perform urgent decompression as soon as safely possible.

Operations include:

• Lumbar laminotomy or laminectomy
• Discectomy
• Adequate decompression of affected roots

Do not delay an available decompression simply to reach an arbitrary 24 or 48 hour threshold.

Outcome generally worsens as established severe sphincter dysfunction persists for longer. Surgical care should therefore proceed without avoidable delay.

CESI

Incomplete CES has meaningful potential for preservation or recovery of bladder function.

Treat urgently before progression to painless retention.

CESR

Established urinary retention is a more severe injury but remains an indication for urgent decompression.

Do not deny surgery because the patient has already developed retention.

Recovery can continue for months after decompression.

Epidural abscess

If CES is caused by infection:

• Obtain blood cultures
• Start appropriate IV antibiotics
• Perform urgent surgical drainage when there is neurological deficit or significant compression

A practical empirical regimen is:

Vancomycin IV plus ceftriaxone 2 g IV every 12 to 24 hours

with broader Gram negative coverage when risk factors warrant.

Epidural haematoma

Urgently reverse anticoagulation and decompress when the haematoma produces significant neurological dysfunction.

Malignant CES

Treat according to spinal oncological compression principles with:

• Urgent MRI
• Dexamethasone when appropriate
• Surgical decompression and stabilisation in suitable patients

or

• Urgent radiotherapy where surgery is inappropriate

Postoperative care

Document postoperative:

• Saddle sensation
• Motor function
• Bladder emptying
• Bowel function

Patients with persistent neurogenic bladder need:

• Urology input
• Intermittent catheterisation where appropriate
• Urodynamic assessment later
• Renal protection

Bowel dysfunction can require a structured bowel programme.

Sexual dysfunction should be addressed rather than omitted from long term follow up.

Prognosis

Motor recovery can occur relatively early.

Bladder, bowel and sexual recovery may continue for many months.

Poorer prognostic features include:

• Complete painless urinary retention before decompression
• Severe saddle anaesthesia
• Longstanding dense neurological deficit
• Severe bilateral weakness

Even severe deficits do not prove that recovery is impossible, so long term rehabilitation and bladder management remain essential.