Neurology · Year 3 · from Neurology

Case 2: Cauda Equina Syndrome

Patient Demographics

  • Age: 45 years
  • Sex: Female
  • Occupation: Nurse

Chief Complaint

"I can't feel when I need to pee and my legs are weak."

History of Present Illness

The patient, a nurse with a 10-year history of chronic low back pain and known L4-L5 disc herniation, presents with acute worsening of symptoms over 48 hours. Three days ago, she had sudden onset of severe low back pain radiating down both legs while lifting a patient at work. Over the past 2 days, she has developed progressive weakness in both legs, difficulty walking, and numbness in her buttocks and inner thighs. Most concerning, she noticed yesterday that she could not feel when her bladder was full - she had an episode of urinary incontinence without awareness. She also has not had a bowel movement in 3 days and has difficulty initiating urination. She denies any trauma, fever, or weight loss. She has tried over-the-counter NSAIDs without relief.

Neurological Examination Findings

Mental Status:

  • Alert, oriented, in significant distress from pain

Motor Examination:

Muscle GroupRightLeft
Hip flexion (L1-L2)4/54/5
Knee extension (L3-L4)4/54/5
Ankle dorsiflexion (L4-L5)3/52/5
Great toe extension (L5)2/52/5
Ankle plantarflexion (S1-S2)3/53/5
  • Upper extremities: 5/5

Sensory Examination:

  • Saddle anesthesia: Decreased sensation over perineum, perianal region, posterior thighs bilaterally (S2-S5 distribution)
  • Decreased sensation: L4-S1 dermatomes bilateral lower extremities
  • Proprioception intact

Reflexes:

  • Upper extremities: 2+
  • Patellar: 1+ bilateral (diminished - L3-L4)
  • Achilles: Absent bilateral (S1-S2)
  • Plantar responses: Absent (cannot elicit)
  • Bulbocavernosus reflex: Absent
  • Anal wink: Absent

Rectal Examination:

  • Decreased anal sphincter tone
  • Absent voluntary anal contraction
  • Decreased perianal sensation (S2-S4)

Bladder:

  • Bladder scan: 650 mL (significant retention)
  • Unable to void

Red Flags Present - Cauda Equina Syndrome

  1. Bilateral leg weakness - motor involvement
  2. Saddle anesthesia - sensory loss in perineal region
  3. Urinary retention with overflow incontinence - bladder dysfunction
  4. Fecal incontinence/constipation - bowel dysfunction
  5. Absent bulbocavernosus reflex - sacral arc dysfunction
  6. Bilateral lower extremity symptoms

Neuro Workup - EMERGENT

MRI Lumbar Spine without and with Contrast (STAT):

  • Large central disc herniation at L4-L5 (14mm posterior protrusion)
  • Severe compression and displacement of the cauda equina nerve roots
  • Nerve roots pushed posteriorly and laterally
  • No enhancement to suggest tumor or infection
  • Mild degenerative changes at L3-L4 and L5-S1 without significant compression

Laboratory Studies:

  • CBC, CMP, coagulation: Normal
  • ESR, CRP: Normal (arguing against infection)

Diagnosis

Cauda Equina Syndrome secondary to L4-L5 disc herniation

Management - SURGICAL EMERGENCY

Immediate Steps:

  1. Foley catheter - decompress bladder
  2. NPO status - preparation for surgery
  3. IV access, labs, type and screen
  4. STAT neurosurgery consultation

Surgical Treatment:

  • Emergent L4-L5 laminectomy and discectomy
  • Surgery performed within 12 hours of presentation
  • Decompression of cauda equina achieved
  • Large disc fragment removed

Intraoperative Findings:

  • Large central disc extrusion compressing thecal sac
  • Cauda equina nerve roots severely compressed but intact
  • Good decompression achieved

Post-operative Care:

  • Neurological monitoring every 4 hours
  • Continued Foley catheter
  • DVT prophylaxis
  • Pain management
  • Physical therapy on post-op day 1

Post-operative Course and Prognosis

Immediate Post-op:

  • Pain significantly improved
  • Motor function: Gradual improvement over weeks
  • Sensory: Saddle sensation slowly returning

At 6 Weeks:

  • Ambulating independently
  • Lower extremity strength 4+/5 bilateral
  • Some residual sensory deficit in S1 distribution

Bladder Function:

  • Initially required intermittent catheterization
  • By 3 months: Able to void spontaneously but with incomplete emptying
  • Urology follow-up for long-term management

Bowel Function:

  • Improved with bowel regimen
  • Occasional urgency but no incontinence

Prognostic Factors

  1. Time to surgery: Most critical factor - surgery within 24-48 hours optimal
  2. Severity of deficits at presentation: Complete deficits = worse prognosis
  3. Duration of symptoms before surgery: Shorter = better
  4. Bladder dysfunction: Often slowest to recover, may be permanent
  5. This patient: Incomplete syndrome, surgery within 12 hours - favorable

Clinical Image

Image Description: Sagittal MRI of the lumbar spine showing a large central disc herniation at L4-L5 causing severe compression of the cauda equina nerve roots within the thecal sac.

Attribution: Image from Wikimedia Commons. Public domain. Source: https://commons.wikimedia.org/wiki/File:CaudaEquinaMRI.jpg

Key Teaching Points

Metastatic Spinal Cord Compression

  1. Back pain is the earliest symptom - often precedes neurological deficits by weeks
  2. Red flags: Pain worse at night, pain with recumbency, known cancer history
  3. MRI entire spine - multiple levels common
  4. Dexamethasone immediately - do not wait for imaging
  5. Surgery vs radiation depends on: Tumor type, stability, single vs multiple levels, deficit severity
  6. Ambulatory status at treatment = ambulatory outcome - time is critical

Cauda Equina Syndrome

  1. Surgical emergency - decompress within 24-48 hours
  2. Cardinal features: Saddle anesthesia, urinary retention, bilateral leg weakness
  3. Cauda equina = LMN lesion (hyporeflexia, flaccid) vs cord = UMN (hyperreflexia, spastic)
  4. Most common cause: Large central disc herniation
  5. Bladder function often last to recover, may be permanently impaired
  6. Always check: Post-void residual, rectal tone, perianal sensation, bulbocavernosus reflex

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