Cauda Equina Syndrome

Cauda equina syndrome is a rare but potentially devastating condition that results from the dysfunction of multiple sacral and lumbar nerve roots in the lumbar vertebral canal that can result in permanent disability (bowel, bladder and sexual dysfunction). All patients presenting to the ED with back pain must be assessed for signs and symptoms of cauda equina syndrome as clinical diagnosis is difficult with potential for considerable morbidity and associated medicolegal implications. Signs and symptoms of cauda equina syndrome mandate urgent spinal surgery referral and MRI lumbosacral spine for consideration of operative management. It is a true spinal emergency.

Source: Lavy, C. et al. Cauda equina syndrome, BMJ;2009, 338:b936

Signs and Symptoms of Cauda Equina Syndrome with Back Pain

  • ‘Saddle anaesthesia’

    • Reduction or loss of perianal sensation.

  • Anal sphincter disturbance:

    • Faecal incontinence

    • Constipation

    • Reduction or loss of anal tone (on PR examination).

  • Urinary symptoms:

    • Incomplete cauda equina syndrome.

Reduced urinary sensation, loss of desire to void, poor stream.

No urinary retention or overflow.

  • Cauda equina syndrome with retention or overflow incontinence.

Incontinence at presentation is a poor prognostic sign.

Patients may present with the above signs or symptoms of cauda equina syndrome in one of three classic patterns:

  • Acutely with back pain as the first symptom of lumbar disc herniation

  • Chronic back pain with slow neurological progression to numbness and urinary symptoms

  • The end-point of a long history of chronic back pain with or without sciatica.


  • Large central lumbar disc herniation at L4/5 and L5/S1 levels.

Source: Lavy, C. et al. Cauda equina syndrome, BMJ;2009, 338:b936

  • Less common causes include:

    • Spinal injury with fractures or subluxation

    • Spinal neoplasms – primary of metastatic

    • Infective abscess or spinal osteomyelitis

    • Iatrogenic – spinal anaesthesia, epidural haematoma (post-operatively), spinal manipulation.

Investigation and Management

When signs or symptoms of cauda equina syndrome are present urgent senior ED doctor review should be sought.

Urgent MRI scan is the investigation of choice. Where this is unavailable a CT scan should be performed (see acute low back pain - investigations)

Routine pre-operative blood tests and investigations (e.g. ECG) should be taken including coagulation studies and a blood group and hold. Blood cultures should be taken if febrile and there is suspicion that spinal abscess or osteomyelitis is the cause of cauda equine syndrome.

Urgent spinal surgery referral should be made without delay and prior to investigations being completed. The patient will most likely require urgent surgical decompression. The timing of surgery is somewhat controversial and will be decided upon clinical and radiological review by the spinal surgeon.

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