Definition

• Cauda equina syndrome (CES) is the collection of symptoms and signs accompanying compression of the cauda equina
• equivalent of spinal cord compression but occurring below L1/2 (termination of the spinal cord)
• a surgical emergency

Assessment

• Frequently missed so have a high index of suspicion
• Not uncommon for patients to present time after time with symptoms suggestive of CES, only for it to be disproved by MRI
• take each presentation seriously as some such patients have eventually been found to have CES

Causes

• Common: massive lumbar disc prolapse
• Tumour
• Trauma
• Epidural haematoma or abscess
• Occasional: progressive lumbar spinal stenosis
• where a relatively small disc prolapse can cause symptomatic CES

History

• Mechanism of injury (if any)
• Pain: (back pain in addition to unilateral or Bilateral sciatica)
• site
• onset and duration
• character
• radiation
• Associated symptoms:
• saddle anaesthesia or altered perianal, perineal or genital sensation
• recent onset bladder dysfunction (e.g. painless urinary retention, overflow incontinence), difficulty initiating micturition or impaired sensation of urinary flow)
• recent onset faecal incontinence or loss of sensation of rectal fullness
• recent onset altered sexual function
• progressive neurological deficit

Investigations

• FBC, U&E, LFT, bone profile, clotting screen
• Myeloma screen
• Urinalysis

Imaging

• MRI scan is the definitive test for cauda equina compression. Request urgently to be carried out within 4 hr of request
• correlates closely with symptomatic CES
• spinal plain film imaging usually unnecessary in addition to MRI
• If suspected unstable fracture, CT scan

Differential diagnosis

• Spinal cord compression
• examine upper limbs as well and examine for sensory level. See Spinal cord compression guideline
• Neurological disorders such as
• demyelination
• transverse myelitis
• Guillain-Barré syndrome
• Bladder/bowel problem
• Effect of pain/analgesia/anxiety

Examination

• Full neurological examination with clear documentation on ASIA chart
• Lower limb strength and reflexes
• Sensory examination of lower limbs and perineum
• Presence or absence of perianal pin-prick sensibility, documented bilaterally
• Presence or absence of voluntary anal contraction
  • note that anal tone is an unreliable sign
• Presence or absence of ‘anal wink’ reflex
  • test anal wink reflex by looking for contraction of anal sphincter whilst testing perianal skin for pinprick sensibility
  • if there is reflex contraction, lower motor neurones are intact and spinal shock has worn off, even if there is spinal cord injury preventing voluntary contraction
  • absent in profound lower motor neurone (i.e. cauda equina as opposed to spinal cord) lesion
• Unless patient to be catheterised anyway (see below), assess post-void residual urine with bladder scanner

• Immediate orthopaedic or neurosurgical referral - do not delay
• MRI scan - to be done within 4 hr of request
• if contraindicated, discuss possibility of CT myelogram with orthopaedic spinal or neurosurgical consultant
• where possible, send patient for MRI scan from Emergency Department before admission to ward
• Remember to keep patient nil-by-mouth until surgical decision has been made
• Analgesia may be required
• If CES strongly suspected, catheterise patient. See Urethral catheterisation guideline
• ask patient to void bladder before catheterisation and document residual urine. A residual over 100 mL is abnormal and may correlate with CES