Cauda Equina Syndrome¶

Definition¶

Cauda equina syndrome (CES) is compression of the cauda equina nerve roots (below the conus medullaris, typically below L1-L2), causing a characteristic clinical syndrome of bilateral leg pain, saddle anesthesia, and bowel/bladder dysfunction. It is a surgical emergency requiring urgent decompression.

Clinical Features¶

Bilateral lower extremity pain and weakness (may be asymmetric)
Saddle anesthesia (perineal/perianal numbness)
Bowel and/or bladder dysfunction (urinary retention or incontinence)
Decreased anal sphincter tone
Sexual dysfunction

Imaging Findings¶

MRI (Urgent — Modality of Choice)¶

Large central disc herniation — Most common cause; typically at L4-5 or L5-S1
Filling of the entire thecal sac — The herniated disc or mass completely effaces the cauda equina
Nerve root compression/displacement — The cauda equina roots are compressed against the posterior thecal sac
DWI — May show restricted diffusion in severely compressed nerve roots

Other Causes¶

Epidural abscess
Epidural hematoma
Tumor (metastasis, ependymoma, schwannoma)
Spinal stenosis (rarely acute enough for CES unless superimposed on chronic stenosis)
Post-surgical hematoma

Clinical Pearl

CES is a surgical emergency — the timing of decompression directly affects neurological outcome. MRI should be obtained urgently (same-day) in any patient with suspected CES. Bladder dysfunction, particularly urinary retention, is the most clinically significant finding and, once established, may be irreversible even after decompression. Decompression within 48 hours is associated with better outcomes, and earlier is better.

Key Points¶

Compression of the cauda equina — bilateral symptoms, saddle anesthesia, bladder dysfunction
Surgical emergency — urgent MRI and decompression within 48 hours
Large central disc herniation is the most common cause
Bladder dysfunction is the most clinically significant finding
MRI shows complete effacement of the cauda equina by the compressing lesion

References¶

Rider LS, Marra EM. Cauda Equina and Conus Medullaris Syndromes. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; updated 2023 Aug 7. Available from: https://www.ncbi.nlm.nih.gov/books/NBK537200/
Gardner A, Gardner E, Morley T. Cauda equina syndrome. Radiopaedia.org. Available from: https://radiopaedia.org/articles/cauda-equina-syndrome
McNamee J, Flynn P, O'Leary S, Love M, Kelly B. Imaging in cauda equina syndrome — a pictorial review. Ulster Med J. 2013;82(2):100-108. Available from: https://pmc.ncbi.nlm.nih.gov/articles/PMC3756868/
Qureshi A, Sell P. Cauda equina syndrome treated by surgical decompression: the influence of timing on surgical outcome. Eur Spine J. 2007;16(12):2143-2151. Available from: https://pubmed.ncbi.nlm.nih.gov/17828560/
Heyes G, Jones M, Verzin E, McLorinan G, Darwish N, Eames N. Influence of timing of surgery on Cauda equina syndrome: outcomes at a national spinal centre. J Orthop. 2018;15(1):210-215. Available from: https://pmc.ncbi.nlm.nih.gov/articles/PMC5895895/
Long B, Koyfman A, Gottlieb M. Evaluation and management of cauda equina syndrome in the emergency department. Am J Emerg Med. 2020;38(1):143-148. Available from: https://pubmed.ncbi.nlm.nih.gov/31471075/
Expert Panel on Neurological Imaging; Hutchins TA, Peckham M, Shah LM, et al. ACR Appropriateness Criteria® Low Back Pain: 2021 Update. J Am Coll Radiol. 2021;18(11S):S361-S379. Available from: https://pubmed.ncbi.nlm.nih.gov/34794594/