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    Cauda Equina and Conus Medullaris Syndromes

    Administration and Operational Issues, Gastrointestinal, Neurological, Orthopedic, Trauma, Urological

    Last Updated May 31, 2023
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    By Julian Marsden, Alexander Forrester

    First 5 Minutes

    Consider in all patients with back pain.

    Prompt neurosurgical or orthopedic consultation and imaging is necessary in suspected cases of cauda equina (CES) and conus medullaris syndromes (CMS).

    Critical information to identify during initial examination includes [1] [2] [3]:

    • Saddle anesthesia.
    • Bladder dysfunction (urinary retention, may manifest as overflow incontinence).
    • Bowel dysfunction (fecal incontinence).
    • Sexual dysfunction.

    Post void residual bladder scanning (PVR) is recommended as an assessment tool in suspected CES.

    A PVR of ≤ 200 ml reduces the likelihood of having CES but does not exclude it; clinical suspicion of CES should always lead to an MRI scan/consultation [4].


    CES and CMS are rare but serious conditions that can be surgical emergencies requiring immediate diagnosis and treatment to prevent permanent neurological damage [2].

    The most recent definition of CES is presence of one or more of the following signs or symptoms:

    • Bladder and/or bowel dysfunction.
    • Reduced sensation in the saddle area.
    • Sexual dysfunction, with possible neurological deficit in the lower limb (motor/sensory loss, reflex change).

    Because the commonest cause of CES is lumbar disc herniation, most cases of CES also have back pain, sciatica or leg pain, sensory loss and/or weakness. However, these are not essential to the definition [3].

    Common causes [1]:

    • Herniated intervertebral disc (L4 – L5 or L5 – S1 for CES; T12 – L2 for CMS). MOST common cause.
    • Degenerative spine conditions (spinal stenosis, spondylolisthesis).
    • Tumor – primary or metastatic.
    • Trauma (even chiropractic manipulation reported rarely).
    • Infection.
    • Ischemia (aortic aneurysm).

    Main difference between Cauda Equina Syndrome (CES) or Conus Medullaris Syndrome (CMS) is a more symmetrical distribution of sensory and motor deficits with CMS.  CMS can give Upper Motor Neuron signs such as spasticity and hyperreflexia.

    Table 1. Common neurological findings of CMS and CES, adapted from Radcliffe (2011).

    Figure 2. (A) lumbar disc herniation L4-5 on sagittal T2-weighted MRI. (B) lumbar disc herniation was observed at L4-5 on sagittal T1-weighted MRI. (C) lumbar disc herniation on left side at L4-5 on axial T2-weighted MRI. Ordinary lumbar disc herniation was observed on the lef | Open-i (nih.gov).

    Diagnostic Process

    • Clinical History
      • Onset of symptoms with emphasis on history of saddle anesthesia, bladder and/or bowel issue, and sexual dysfunction [3].
    • Physical Exam [5]
      • Saddle area for loss of sensation (more valid and reliable indicator of CES or CMS compared to rectal examination).
      • Rectal examination for anal tone.
      • Establish presence of any dermatome, myotome, or reflex change.
    • Imaging
      • MRI is gold standard for diagnosing and differentiating between CES and CMS [6].
      • CT can detect bony abnormalities and some soft tissue lesions [1].
      • X-ray of the lumbar spine can be used as an initial screening tool.
    • Bladder scan (PVR) [4]
      • Post void residual bladder scanning (PVR) is recommended as an assessment tool in suspected CES.
      • A PVR of ≤ 200 ml reduces the likelihood of having CES but does not exclude it; clinical suspicion of CES or CMS should always lead to an MRI scan.
    • Urinalysis rule out UTI.
    • Blood tests (limited utility) – normal CRP may rule out infection.

    Recommended Treatment

    • Initial stratification of CES occurs follows imaging, completed by consulting specialists (neurosurgery or orthopedics).
    • Patients that do not have compression of the CE or CM can be discharged with pain management in consultation (and follow-up) with neurosurgery/orthopedics [7] [1].
    • Patients may be admitted and treated for pain relief and further investigations if neurological symptoms continue to progress.
    • Patients with pathology indicating CES or CMS require surgical decompression of the intervertebral disc [7] [2]. Patients that receive surgery within 48 hours typically have better outcomes. No statistical difference for those receiving surgery within 24 hours or 48 hours [1].

    Criteria For Hospital Admission

    Guidance for admitting patients with CES or CMS:

    • Confirmed CES or CMS diagnosis via clinical history, physical exam, and pathology seen on imaging.
    • Consult with neurosurgery or orthopedic surgery prior to admitting.
    • Objective or progressive neurological deficits with normal lumbosacral MRI (further investigation needed).

    Criteria For Transfer To Another Facility

    MRI is the gold standard for diagnosing CES or CMS. Imaging guides the treatment pathway [1]. Therefore:

    • Diagnostic imaging modalities (MRI) not available.
    • Surgical decompression of CES or CMS pathology not possible at facility.
    • Medical management not possible due to resource limitations.

    This is done in consult with the receiving surgical service.

    Criteria For Close Observation And/or Consult

    • Consult acute pain service for pain management.
    • Consult the on-call spine surgery service (neurosurgery or orthopedic surgery) if clinical history, physical exam and MRI indicate CES or CMS.

    Criteria For Safe Discharge Home

    • Pain is controlled.
    • Patient able to ambulate.
    • With consultant agreement and follow-up in place.

    Quality Of Evidence?


    Majority of literature based on retrospective case studies. Given that both CES, and to a greater extend CMS, are rare conditions the number of cases reviewed, and the variability in results makes this evidence.


    Related Information


    Reference List

    1. Kuris et al. Evaluation and Management of Cauda Equina Syndrome. The American Journal of Medicine 2021, 1483-1489. doi:10.1016/j.amjmed.2021.07.021

    2. Radcliff et al. Current management review of thoracolumbar cord syndromes. The Spine Journal 2011, 11, 884-892. doi:10.1016/j.spinee.2011.07.022

    3. Lavy et al. Cauda equina syndrome—a practical guide to definition. International Orhopaedics 2022, 46, 165-169. doi:10.1007/s00264-021-05273-1

    4. Todd et al. Post‑void bladder ultrasound in suspected cauda equina syndrome—data from medicolegal cases and relevance to magnetic resonance imaging scanning. International Orthopaedics 2022, 46, 1375-1380. doi:10.1007/s00264-022-05341-0

    5. Greenhalgh et al. Assessment and management of cauda equina syndrome. Musculoskeletal Science and Practice 2018, 37, 69-74. doi:10.1016/j.msksp.2018.06.002

    6. Brouwers et al. Definitions of traumatic conus medullaris and cauda equina syndrome: a systematic literature review. Spinal Cord 2017, 55, 886-890. doi:10.1038/sc.2017.54

    7. Todd & Dickson. Standards of care in cauda equina syndrome. British Journal of Neurosurgery 2016, 30(5), 518-522. doi:10.1080/02688697.2016.1187254


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