What are cauda equina syndrome and conus medullaris syndrome?

Cauda Equina Syndrome and Conus Medullaris Syndrome

Cauda equina syndrome (CES) is a neurological emergency characterized by compression of the lumbosacral nerve roots causing urinary retention, saddle anesthesia, bilateral radiculopathy, and bowel/bladder dysfunction, while conus medullaris syndrome (CMS) results from injury to the terminal portion of the spinal cord with distinct neurological manifestations. 1, 2

Cauda Equina Syndrome

Definition and Anatomy

• Cauda equina syndrome results from compression of the lumbosacral nerve roots below the level of the conus medullaris (the terminal portion of the spinal cord) 2
• Most commonly caused by massive midline disc herniation at L4-L5 and L5-S1 levels 1
• Rare condition with an estimated prevalence of 0.04% among patients with low back pain 1

Clinical Presentation

• Early Warning Signs ("Red Flags"):

  • Bilateral radiculopathy (bilateral radicular pain, sensory disturbance, or motor weakness) 3, 4
  • New changes in bladder function with preserved control (hesitancy, poor stream, urgency) 3, 1
  • Progressive neurological deficits in the legs 3, 4
  • Subjective and/or objective loss of perineal sensation 3

• Late Signs ("White Flags"):

  • Urinary retention or incontinence (most frequent finding with 90% sensitivity) - often indicates irreversible damage 3, 1
  • Complete perineal anesthesia 3, 4
  • Fecal incontinence 3, 4

Diagnostic Approach

• Immediate MRI is essential for all suspected cases and should be performed as part of triage 3
• No single symptom or sign has high positive predictive value in isolation 1
• MRI confirmation rates are typically only 14-33%, with emergency surgery rates of only 4-7% 3

Management

• Emergency decompressive surgery is indicated for:
  • Suspected CES with severe radiological compression 3
  • All cases of incomplete CES 3
• Better outcomes are associated with surgery within 12-72 hours of symptom onset 3
• Steroids are not indicated or recommended in the emergency management of suspected CES 3

Prognosis

• Patients treated at the suspected or incomplete stage typically achieve normal or socially normal bladder and bowel control 3
• Patients treated at the complete stage have variable recovery, with 48-93% showing some improvement 3
• Only a minority of patients with severe deficits post-CES return to work 3

Conus Medullaris Syndrome

Definition and Anatomy

• Conus medullaris syndrome results from injury to the terminal portion of the spinal cord itself (conus medullaris) 2, 5
• Typically occurs from injuries at the thoracolumbar junction 5

Clinical Presentation

• Can present with symptoms similar to cauda equina syndrome but with some key differences 2, 5:
  • More symmetric motor and sensory deficits 2
  • Earlier onset of urinary retention and sexual dysfunction 5
  • Preservation of reflexes may occur (unlike CES) 6
  • Back pain with bilateral symptoms 5

Management

• Similar to CES, surgical decompression is recommended within 48 hours, preferably within 24 hours 2
• No data supports the role of steroids in acute CMS 2

Differentiating CES from CMS

• Key Differences:
  • CES affects the nerve roots below the spinal cord, while CMS affects the terminal portion of the spinal cord itself 2, 5
  • CMS typically presents with more symmetric findings 2
  • Reflexes may be preserved in CMS but are often absent in CES 6
  • CES may sometimes mimic CMS, requiring careful evaluation of the entire lumbosacral region 6

Common Pitfalls to Avoid

• Waiting for complete urinary retention before referral (it's a late sign) 3, 4
• Delaying MRI when CES is suspected 3
• Relying on late "white flag" symptoms for diagnosis, which often results in permanent neurological damage 4
• Inadequate assessment leading to missed diagnosis 4
• Failing to examine the lower cauda equina when symptoms suggest conus medullaris compression 6