FND Education Project

REFERENCE · DIAGNOSIS

Scan-Negative Cauda Equina Presentations

Refers to:

  • a person presenting with symptoms that raise concern for cauda equina syndrome, such as new bladder or bowel dysfunction, saddle or genital sensory change, leg weakness or numbness, or severe back/leg pain;
  • appropriate spinal assessment and imaging that do not show cauda equina compression sufficient to explain the presentation; and
  • the need to work out what combination of spinal, neurological, urological, pain-related, medication-related, pelvic-floor, functional or other factors best explains the person’s symptoms.

Scope boundary: Scan-negative cauda equina syndrome is not simply another name for FND. It describes a cauda-equina-like presentation without the expected compressive lesion on imaging. Some people in scan-negative cohorts have functional neurological features, but those features must be assessed positively rather than inferred from a negative scan. A person can also have genuine spinal disease, pain or injury together with functional symptoms. [1][2]

[!IMPORTANT] New urinary retention or incontinence, new bowel dysfunction, saddle/genital numbness, rapidly changing leg weakness, or another possible cauda equina presentation requires urgent medical assessment. A previous scan-negative episode or an FND diagnosis must not be used to dismiss a new emergency presentation.

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A scan-negative cauda equina presentation means that symptoms looked concerning enough for cauda equina syndrome to be investigated, but the scan did not show the kind of nerve-root compression that would explain classic compressive cauda equina syndrome.

That does not mean the symptoms were imaginary, and it does not by itself prove FND. The next question is what is actually contributing to the symptoms. Depending on the person, that may include pain, a back injury or other spinal problem, medication effects, bladder or pelvic-floor dysfunction, another neurological condition, functional weakness or sensory symptoms, or more than one process at the same time. [1]

If a clinician thinks part of the presentation is functional, that conclusion should rest on positive evidence from the neurological examination or another appropriate assessment. A normal or non-compressive MRI alone is not a positive FND sign.

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For Family, Friends, and Other Supporters

Take new bladder, bowel, saddle-sensation or major leg changes seriously, even when the person has had a previous scan-negative episode.

After an emergency cause has been assessed, practical support may include help with mobility, toileting, transport, pain management, appointments and following the agreed bladder or rehabilitation plan. Do not assume that reassurance, distraction or psychological treatment is the correct response simply because imaging did not show cauda equina compression.

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For Clinicians and the Care Team

First establish the emergency question

When the presentation could represent compressive cauda equina syndrome, assess and investigate it on that basis. The term scan-negative should only be used after the relevant structural emergency has been considered and imaging interpreted in the clinical context.

Then separate the remaining questions

After compression is not demonstrated, avoid collapsing the presentation into one diagnosis. Consider, according to the phenotype:

  • spinal or radicular pain and non-cauda-equina structural disease;
  • bladder retention, urgency or incontinence from urological, medication-related or pelvic-floor causes;
  • bowel and sexual dysfunction;
  • pain-related motor inhibition or severe guarding;
  • functional limb weakness, sensory symptoms or other positive functional signs;
  • other neurological or medical explanations; and
  • coexistence of more than one condition.

A functional formulation should identify the positive evidence for the functional component. It should not be inferred from normal imaging, psychiatric history, stress or the absence of a surgical lesion.

Keep the terminology precise

Compressive cauda equina syndrome refers to the clinical syndrome caused by compression of the cauda equina requiring urgent management.

Scan-negative cauda equina presentation/syndrome describes a clinically concerning presentation in which imaging does not show compression sufficient to account for the syndrome.

Functional neurological symptoms may be part of some scan-negative presentations, but the terms are not interchangeable.

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Research and Sources

The main source currently used by this starter page is the retrospective cohort by Hoeritzauer and colleagues comparing scan-positive and scan-negative suspected cauda equina presentations. It supports the importance of distinguishing a negative compressive scan from a conclusion that symptoms are functional or psychological. The Bennett review provides broader FND context but should not be used by itself to define scan-negative cauda equina syndrome. A later expansion should add current spinal-surgery, emergency, neurourology and pelvic-floor guidance. [1][2]

Citation Full citation
[1] Hoeritzauer I, Pronin S, Carson A, Statham P, Demetriades AK, Stone J. The clinical features and outcome of scan-negative and scan-positive cases in suspected cauda equina syndrome: a retrospective study of 276 patients. Journal of Neurology. 2018;265(12):2916–2926. https://doi.org/10.1007/s00415-018-9078-2. FND-CIT-0016.
[2] Bennett K, Diamond C, Hoeritzauer I, Gardiner P, McWhirter L, Carson A, Stone J. A practical review of functional neurological disorder (FND) for the general physician. Clinical Medicine. 2021;21(1):28–36. https://doi.org/10.7861/clinmed.2020-0987. FND-CIT-0001.

Starter page added September 29, 2026 · spinal-surgery, emergency medicine, neurourology, pelvic-floor, neurology, lived-experience and accessibility review pending

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