EM@3AM – Cauda Equina Syndrome

Author: Erica Simon, DO, MHA (@E_M_Simon, EM Chief Resident, SAUSHEC, USAF) // Edited by: Alex Koyfman, MD (@EMHighAK, EM Attending Physician, UT Southwestern Medical Center / Parkland Memorial Hospital) and Brit Long, MD (@long_brit, EM Attending Physician, SAUSHEC, USAF)

Welcome to EM@3AM, an emdocs series designed to foster your working knowledge by providing an expedited review of clinical basics. We’ll keep it short, while you keep that EM brain sharp.

A 72-year-old male, with a history of stage IV prostate cancer, presents to the emergency department for fecal incontinence and right lower extremity weakness. The man reports the sudden onset of his symptoms eight hours prior to arrival.  He denies a history of spinal surgery, recent trauma, anticoagulation, IVDA, and fevers. Review of systems is significant for chronic low back pain.

Initial VS: BP 134/82, HR 88, T 98.6F Oral, RR 14, SpO2 98% on room air.

Examination is remarkable for decreased rectal tone, 1+ right patellar and Achilles reflexes, diffuse atrophy of the right knee extensors, and decreased pinprick/light touch sensation of the S1 and S2 dermatomes (R > L).

What’s the next step in your evaluation and treatment?

Answer: Cauda Equina Syndrome (CES)1-3

  • Etiology: Resulting from lesions compressing the conus medullaris and nerve roots (e.g. herniated disk, bone fragment, hematoma, infection, tumor, vascular insufficiency), usually below the level of L1.1,2 
  • Presentation: Patients may present with low back pain, leg pain, lower extremity paralysis or paresthesias, saddle anesthesia, impotence and/or bowel/bladder dysfunction.
    • Urinary retention is the most consistent finding (sensitivity of 90%).3 
  • Evaluation:
    • Perform a thorough H&P:
      • Question specifically regarding: spinal instrumentation (to include injection), recent trauma, anticoagulation, IVDA, B symptoms, or history of malignancy.
    • Examination:
      • Neuro: Most often affecting levels below L1:
        • Deficits of the lower extremities; frequently asymmetrical, unilateral, and c/w lower motor neuron signs (areflexia, hypotonia, atrophy if chronic cord compression).
        • Absent or decreased rectal tone.
        • Absent or decreased bulbercavernosus reflex.
      • Abdomen: Palpable bladder secondary to urinary retention.
    • Imaging:
      • MRI is the imaging modality of choice. CT myelography may be utilized in patients ineligible for MRI (e.g. pacemaker or metal implants).2
      • Bedside ultrasound: post void residual of 100-200 mL in a patient without a history of voiding difficulty suggests a neurologic etiology.2
  • Treatment:
    • Surgical emergency => neurosurgical consultation:
      • Surgical decompression within a 24-hour window is advised for preservation of function.
  • Pearls:
    • Most meaningful indicator of recovery in CES: initial severity of neurologic deficit. Incomplete injury = more likely to demonstrate improvement post decompression.1
    • Examination should include testing of sensory function (pinprick and light touch) of the sacral dermatomes => sacral sparing may indicate an incomplete lesion and thus an improved prognosis.2
    • Conus medullaris syndrome differs from CES in that1:
      • Deficits are often symmetric, affecting the bilateral lower extremities.
      • Examination is frequently significant for signs of upper motor neuron dysfunction: hyperreflexia and spasticity.
      • T11-L1 spinal cord levels are commonly involved.



  1. Seecharan D, Arnold P. Spinal Cord Injuries and Syndromes. In Textbook of the Cervical Spine. Philadelphia, Saunders. 2015; 19: 192-196.
  2. Perron A, Huff J. Spinal Cord Disorders. In Rosen’s Emergency Medicine. Philadelphia, Saunders. 2014; 106: 1419-1427.e2.
  3. Jailoh I, Minhas P. Delays in the treatment of cauda equina syndrome due to its variable clinical features in patients presenting to the emergency department. Emerg Med J. 2007; 24:33.


For Additional Reading:

Cauda Equina Syndrome:

Cauda Equina Syndrome

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