Cauda equina syndrome


Cauda equina and filum terminale seen from behind. The dura mater has been opened and spread out, and the arachnoid mater has been removed.
  • The cauda equina (Latin for "horse's tail") begins at the 2nd Lumbar space extending down to the beginning of the sacral nerves. It is distal to the tapered end of the spinal cord, or conus medularis.[1]

Epidural compression syndromes

Sensory dermatome by spinal level.

Clinical Features

Approximate area of "saddle anesthesia" seen from posterior (yellow highlight).
  • Most common in young men[2]
  • The onset of perineal anesthesia associated with bladder dysfunction is typical of the start of cauda equina syndrome and the time at which the clock starts on diagnosis and management.[3]
  • The most common presenting symptom is urinary retention with or without resultant overflow urinary incontinence.
    • Painless urinary retention often has the greatest predictive value as a stand-alone symptom, but it is unfortunately indicative of late, often irreversible cauda equina syndrome[4]

Epidural compression syndromes table[5]

Syndrome Spinal cord compression Conus medullaris syndrome Cauda equina syndrome
Location of lesion Lesions at vertebral level L2
Spontaneous pain Unusual and not severe; bilateral and symmetrical in perineum or thighs Often very prominent and severe, asymmetrical, radicular
Motor findings Deficits usually affect both legs but are often asymmetric Not severe, symmetrical; rarely twitches May be severe, asymmetrical, fibrillary twitches of paralyzed muscles are common
Sensory findings Weakness in lower extremities, paresthesias/sensory deficits, gait difficulty Saddle distribution, bilateral, symmetrical, disassociated sensory loss (impaired pain and temperature with sparing of tactile) Saddle distribution (75% pts), may be asymmetrical, no dissociation of sensory loss
Reflex changes Achilles reflex may be absent Patellar and Achilles reflexes may be absent
Sphincter disturbance Bladder and rectal sphincter paralysis usually reflect the involvement of S3-S5 nerve roots Early and marked (both urinary and fecal) Late and less severe (60-80% pts)
Male sexual function Impaired early Impairment less severe
Onset Sudden and bilateral Gradual and unilateral
Other Urinary retention with or without overflow incontinence (Sn 90%, Sp 95%)

Differential Diagnosis

Lower Back Pain

Spinal Cord Syndromes


MRI of an abscess causing cauda equina syndrome.
  • Emergent MRI
    • If considering compression due to neoplasm obtain scan of entire spine
  • Consider Bladder scan/ultrasound for bladder volume (post-void residual)


General Epidural Compression Syndrome Management

  • Dexamethasone: at least 16 mg IV as soon as possible after assessment[6]
    • Note: dexamethasone can be used to reduce compressive edema from epidural metastases, but is more likely to worsen an infection from spinal epidural abscess.
  • Consult spine service
  • Consider foley for bladder decompression
  • Consider dexamethasone 4 mg q4 hours after first dose


  • Admit

See Also


  1. Cohen MS, Wall EJ, Kerber CW, et al. The Anatomy of the Cauda Equina on CT Scans and MRI. J Bone Joint Surg Br 1991; 73 (3): 381-84.
  2. Rider LS, Marra EM. Cauda Equina And Conus Medullaris Syndromes. In: StatPearls. StatPearls Publishing; 2023. Accessed March 29, 2023.
  3. Quaile A. Cauda equina syndrome-the questions. Int Orthop. 2019;43(4):957-961. doi:10.1007/s00264-018-4208-0
  4. Todd NV. Guidelines for cauda equina syndrome. Red flags and white flags. Systematic review and implications for triage. Br J Neurosurg. 2017;31(3):336-339. doi:10.1080/02688697.2017.1297364
  5. Bradley WG. Neurology in Clinical Practice: Principles of diagnosis and management. P363
  6. Metastatic spinal cord compression: Diagnosis and management of patients at risk of or with metastatic spinal cord compression. Full Guideline. November 2008. Developed for NICE by the National Collaborating Centre for Cancer. ©2008 National Collaborating Centre for Cancer