see also:

• back pain in the ED
• sensory & motor testing including dermatomes, myotomes, reflexes, coordination & balance

• an important complication of various conditions which cause low back pain (although it can occur without back pain), which requires urgent MRI to avoid delay in surgical Rx which increases risk of permanent urinary +/- faecal incontinence due to neuropraxia of the S2-4 nerve roots
• early recognition and treatment of CES is associated with improved outcome with respect to bladder function.
• failure to recognise and treat this condition expediently may have outcome and medico-legal implications
• mostly due to issues at lumbar levels L4/L5 (and L5/S1, and to a lesser extent, L3/L4) as these are the levels with the most densely packed nerve roots where the sacral level nerves are most vulnerable, and are the commonest levels for major lumbar disc herniation
  • NB. spinal cord itself typically ends near the L1/L2 vertebral level
  • whilst L2/L3 issues can cause CES, these cases are rare
• 2 main groups of presentations:
  • acute onset within 24 hours (85% of cases)
    • most will have had chronic lumbar back pains but some may not have a prior history of pain until this episode
  • gradual progression to CES in patients who have chronic back pain and sciatica

• incidence: 1 per 33,000-100,000 annually
• CES accounts for 1-10% of L4/L5 or L5/S1 lumbar disc prolapses which require surgical Rx

• lumbar disc prolapse - ~50% of cases - mostly L4/L5 but also L5/S1 and to lesser extent L3/L4
• lumbar canal stenosis - 15-30% of cases
• spinal trauma with fractures
• spinal tumours
• epidural abscess
• complication of spinal anaesthesia or similar procedures
• spina bifida
• spinal haemorrhage
• intravascular lymphomatosis
• lipomas
• multiple sclerosis (MS)
• late stage ankylosing spondylitis (AS)
• sarcoidosis
• propagated deep venous thrombosis (DVT) of the spinal veins
• ivc thrombosis
• dural sac ectasia (associated with connective tissue (CT) disorders, particularly Marfan's syndrome)

• urinary symptoms - eg. incontinence or retention (S2-S4)
• saddle anaesthesia (S2-S4)
• +/- reduced anal tone (S2-S4)
• +/- faecal incontinence (S2-S4)
• usually in a setting of acute or chronic low back pain +/- radicular pain to buttocks &/or legs
  • it may also present with acute foot drop although this is usually L4 level (loss of Achilles reflex and foot eversion is mainly S1 and some S2 while great toe dorsiflexion and hip abduction and 1st dorsal web space sensation is L5)
• “complete lesions” are typically characterised by painless urinary retention with overflow incontinence.
• “incomplete lesions” present with symptoms of impaired bladder function including urinary frequency, painful urinary retention or inability to void in past 6hrs, and/or urge incontinence, +/- muscle weakness in legs.

• suggestive features
  • acute urinary retention in setting of back pain (~90% sens.)
  • bilateral sciatica + urinary symptoms + perianal sensory changes (60-70% sens.)
  • urgent MRI assessment in all patients who present with new onset urinary symptoms in the context of lumbar back pain or sciatica.
    • ~40% of urgent scans fail to show structural evidence of CES as clinical findings have low specificity and some cases may be functional
• radiologic CES
  • usually defined as an over 75% occlusion of the spinal canal or an absence of cerebrospinal fluid (CSF) visible around the cauda equina
  • patients without clinical CES criteria but radiologic CES criteria
    • occurs in approximately 11% of referrals with radiologic CES criteria²⁾
    • these patients are usually generally referred with only sciatica, sciatica with leg weakness, foot drop or back pain and don't have CES symptoms
    • most appear to be due to L4/L5 level issues - mostly due to disc herniation, and most will have significant ongoing chronic pains even after emergent or elective surgery - particular issues in this group were with standing, lifting weights and pain intensity, only a minority (<15%) developed chronic bladder or significant sexual dysfunction issues³⁾
• clinical CES
  • occurs in ~19% of cases of suspected CES⁴⁾
  • radiologic confirmation plus at least one of the following must be present:
    • bladder and/or bowel dysfunction
    • reduced sensation in the saddle area
    • sexual dysfunction; with possible neurological deficit in the lower limb (motor/sensory loss, reflex change)

• patients with severe pain anywhere may develop urinary difficulties, presumably due to increased sympathetic tone
• conus medullaris syndrome
  • the most distal bulbous part of the spinal cord at L1-2 is called the conus medullaris
  • aetiology is similar to that of cauda equina syndrome except the usual lumbar disk prolapses are too low to affect the cord
  • clinical features tend to overlap those of cauda equina syndrome however, neurology involving higher level dermatomes and myotomes may be affected, and reflexes are generally hyper-reflexic if UMN lesion rather than LMN lesions as in cauda equina syndrome.
• spinal cord compression from abscess, tuberculosis (TB), haematoma or malignancy
• “functional”

• is it complete or incomplete lesion:
  • post-void bladder scan to exclude urinary retention (if can't pass urine just do bladder scan ASAP)
    • a post-void residual of > 200mL is highly suggestive of CES in the context of other features
    • a post-void residual of < 100mL should not be used to exclude clinical CES as it may be incomplete CES which is still needing emergent Rx
  • is there overflow or urge incontinence?
  • check perianal sensation and anal tone
• is there evidence of, or risk for malignancy and spinal cord compression?
• if urinary retention then insert IDC
• urgent MRI scan - same day!
• discuss with neurosurgeons ASAP - consider doing so even before the MRI referral as their support may be important to ensure time critical MRI scanning!
  • the window of opportunity to surgically reduce permanent disability in incomplete CES without urinary retention is only 24-48hrs
  • appears to be no benefit in Rx within 24hrs compared to Rx within 24-48hrs, although re-analaysis suggests some patients with incomplete CES may have further benefit in surgery under 24hrs ⁵⁾⁶⁾
  • general consensus is that surgery should be performed within 48hrs of onset but avoid overnight surgery when complication rates are likely to be higher ⁷⁾
  • patients who develop urinary retention early after disc prolapse (complete CES) are far less likely to benefit from surgery as the damage is probably irreversible within 6hrs based upon physiologic studies, and outcome studies of this group demonstrate generally poor outcomes suggesting the “die is cast” before surgery is possible
  • 75% of all CES cases will eventually have acceptable urological function and 20% of all CES patients will have a poor outcome usually with the need for ongoing treatment e.g. management of sexual dysfunction, self catheterisation, colostomy, urological and gynaecological surgery, spinal injuries rehabilitation and psycho-social support.⁸⁾