Missed cauda equina syndrome

Cauda equina syndrome (CES) is an inherently challenging diagnosis to make. It is a needle in a haystack, with back pain being very common but CES being very rare. It carries devastating consequences for the patient and high medico-legal risks for providers.

A few weeks ago Steven Chiverton, a 39-year old man, was left paraplegic after his CES was missed multiple times. As he explained, “All I can do now is to try to make sure lessons are learned. Too many people are having their lives ruined unnecessarily by this awful condition. Doctors need to be alert to cauda equina syndrome and that scans and operations need to be done urgently when the red flags appear otherwise the chance of that patient recovering diminishes with every hour that passes.”

Like many emergencies, the “classic” presentation of CES is defined by its late findings: saddle anesthesia, bowel/bladder incontinence, and leg weakness. But if patients have to wait until they are incontinent and paraplegic to get an MRI, like Mr. Chiverton did, they will not benefit from the diagnosis and potential early surgical treatment. Instead we need to get MRIs on patients before these late complications develop. This is obviously challenging given the rarity of the condition, the limits of the clinical exam and the difficulties in accessing MRI and neurosurgery, but can hopefully be improved by considering the progression of CES and the possibility of early diagnosis.

Below is a brief overview of the pathophysiology, clinical findings, and stratification of suspected CES, with an emphasis on early diagnosis.


CAUDA EQUINA SYNDROME: compression of the lumbo-sacral nerve roots

  • etiology
    • traumatic: blunt/penetrating injury, post-operative
    • atraumatic: central disc protrusion, tumour, epidural abscess, epidural hematoma, spinal stenosis
  • symptoms: acute or gradual
    • back pain, bilateral radiculopathy
    • numb: perianal, bladder sensation
    • weak: rectal incontinence, urinary retention, erectile dysfunction, lower extremity weakness
  • diagnosis: MRI identify compression and cause (CT can miss disc, tumour, abscess, hematoma)
  • treatment: urgent/emergent neurosurgical decompression



Unfortunately there is poor correlation between the clinical exam and MRI findings, and by the time the patient has the most obvious clinical findings they often have irreversible neurological damage:

  • Predictive value of clinical characteristics in patients with suspected cauda equine syndrome. Eur J Neurol 2009 Mar:16(3):416-9
    • Best predictor >500cc in bladder
    • Other: bilateral sciatica, urinary retention, rectal incontinence
  • Does patient history and physical examination predict MRI proven cauda equine syndrome? Evid Based Spine Car J 2011 Nov;2(4):27-33
    • Systematic review of literature,  comparing symptoms/signs with MRI
    • Symptoms: low back pain, bilateral sciatica, bladder retention, bladder incontinence, frequent urination, decreased urinary sensation, bowel incontinence
    • Signs: saddle numbness, reduced anal tone
    • No sign/symptom have good likelihood ratios


  • Does rectal examination have any value in the clinical diagnosis of cauda equine syndrome. Br J Neurosurg 2013 Apr;27(2): 256-9
    • 57 suspected, 13 confirmed, DRE did not help discriminate


  • Reliability of clinical assessment in diagnosing cauda equine syndrome. Br J Neurosurg 2010 Aug;24(4):383-6
    • 80 patients suspected, 15 confirmed and operated
    • saddle anesthesia only finding with significant correlation to MRI
    • “As there is no symptom or sign which has an absolute predictive value in establishing the diagnosis of CES, any patient in whom a reasonable suspicion of CES arises must undergo urgent MRI to exclude this diagnosis.”



CES has been defined with respect to its neurological complications, but these can be stratified by their timing and their response to surgery. There have been a number of different classification systems proposed, but they share the emphasis on progression and early recognition:

  • Clinical classification of cauda equine syndrome for proper treatment. Act Orthop 2010 Jun;81(3): 391-5
    • 39 patients with confirmed CES divided into four stages based on progression
      • group 1: preclinical = low back pain. Surgery prevents development of symptoms
      • group 2: early = saddle sensory disturbance, bilateral sciatica. Surgery restores function
      • group 3: middle = saddle sensory disturbance, bowel/bladder/sexual dysfunction, leg weakness. Good chance of surgical improvement
      • group 4: late = saddle anesthesia, bowel incontinence. Low chance of surgical improvement
    • It’s unrealistic to rush for MRIs in the preclinical stage, but this emphasizes the red flag of bilateral sciatica and the importance of assessing for subtle saddle sensory disturbances before anesthesia, and of assessing bladder dysfunction before incontinence

This is confirmed by a look at medico-legal literature:

  • Cauda equine syndrome: a review of the current clinical and medico-legal position. Eur Spine J 2011 May;20(5):690-697
    • Stratification
      • CES-Incomplete: altered urinary sensation, loss of desire to void, poor stream, need to strain, partial saddle sensory disturbance, trigone sensation intact (urge to pee when pull on foley)
      • CES-Retention: painless urinary retention, overflow incontinence, saddle anesthesia, trigone sensation gone
    • Presentations: half of patients present with CESI, half with CESR
    • Goal: diagnose and surgically treat before CESI progresses to CESR
  • Causes and outcomes of cauda equine syndrome in medico-legal practice: a single neurosurgical experience of 40 consecutive cases. Brit J Neurosurg, Aug 2011; 25(4):503-8
    • Classified into four groups
      • I post-op for unilateral sciatica: nerve injury or extradural hematoma
      • II bilateral sciatica, at risk for CES from central disc prolapse
      • III CES-Incomplete
      • IV CES-Retention
    • Excluding post-op patients there were 28 patients who progressed to neuro deficits: 1 had unilateral radiculopathy, 11 had bilateral radiculopathy, 14 had CESI, 2 had CESR.
    • This underscores the red flag of bilateral radiculopathy, and the need for diagnosing CESI before it progresses to CESR

A similar classification system proposes four categories, ranging from suspected to complete:

  • Standard of care in cauda equine syndrome. Brit J Neurosurg 2016, 30:5, 518-22
    • CES-Suspected: bilateral radiculopathy
      • unilateral radiculopathy, even with a large disc prolapse, is at low risk for CES
    • CES-Incomplete: altered urinary sensation, loss of desire to void, poor stream, need to strain
    • CES-Retention: painless urinary retention, overflow incontinent
    • CES-Complete: paralyzed bowel/bladder



In summary, CES is rare but devastating, and we need a high index of suspicion in order to diagnose it early before it progresses to neurological complications. What I took away from this review was the reassurance that unilateral radiculopathies rarely develop into CES, and that instead we should be on the lookout for early signs of CES: bilateral radiculopathy,  subtle sensory/bladder disturbances, and post-void residual:

  • History
    • risk factors: trauma, surgery, cancer, anticoagulants, immunocompromised,
    • pain: severe, bilateral radiculopathy, multiple visits
    • weak: bowel, bladder, sexual, lower extremities
    • numb: perianal, perineal, bladder
  • Physical
    • weak: rectal tone, lower extremity strength
    • numb: perianal
  • Bedside test
    • post-void residual
    • trigone sensation
  • Stratification
    • CESS: bilateral radiculopathy
    • CESI: altered sensation/function
    • CESR: retention
    • CESC: paralysis
  • Imaging
    • “As there is no symptom or sign which has an absolute predictive value in establishing the diagnosis of CES, any patient in whom a reasonable suspicion of CES arises must undergo urgent MRI to exclude this diagnosis.”
  • Consultation
    • as there are often delays in getting MRI and further delays in mobilizing operating room resources, consider early neurosurgical consultation if suspecting CESI/CESR as these treatments are the most time sensitive
  • Discharge instructions:
    • for back pain patients who are not suspected of CES (ie the vast majority of back pain patients), consider adding bilateral radiculopathies or subtle bladder/perianal sensory disturbances to your list of reasons they should return


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