Traumatic Cauda Equina Syndrome

In most adults the spinal cord itself ends near the bottom of the ribcage. Below this, the canal is filled with the nerve roots of the cauda equina, which travel down before exiting the spine at their own levels to supply the legs, bladder, bowel and the saddle region. Because these are nerve roots rather than spinal cord, an injury here produces a "lower motor neuron" pattern — flaccid (floppy) rather than stiff weakness — and the effects are often asymmetrical, reflecting which roots are compressed.

Traumatic cauda equina syndrome usually results from a fracture of the lower (lumbar) spine, particularly a burst fracture in which fragments of bone are pushed backwards into the canal and squeeze the nerve roots. It can also occur with fracture-dislocations and, occasionally, when a nerve root becomes trapped in a tear of the tough membrane surrounding the roots. High-energy injuries such as falls from height and road traffic collisions are typical causes. (Away from trauma, the commonest overall cause of cauda equina syndrome is a large disc prolapse.)

The symptoms reflect compression of the nerve roots and often include severe pain radiating into the legs, weakness of the legs or feet that may be uneven between the two sides, and numbness. The features that most concern doctors — the "red flags" — are numbness or altered sensation around the saddle area, difficulty passing or controlling urine (including a sense of not fully emptying the bladder or, in more advanced cases, painless retention with overflow), loss of bowel control, and reduced sexual sensation. These features, particularly after an injury to the lower spine, are treated as an emergency.

The diagnosis is confirmed with an urgent MRI scan of the lower spine, which shows the nerve roots and any compression from bone, disc or other cause. A CT scan is very helpful in the traumatic form because it shows the fracture and the position of bone fragments. Assessment of bladder function (including whether the bladder is emptying properly), saddle sensation and leg strength is central to the clinical assessment and to planning treatment.

Traumatic cauda equina syndrome is treated as a surgical emergency. The aim of surgery is to take the pressure off the compressed nerve roots and to stabilise the fractured spine, usually through decompression and instrumentation appropriate to the injury pattern. The exact operation depends on the level and nature of the fracture. The precise ideal timing of surgery is debated, but the principle is clear: prompt decompression gives the best chance of recovery of bladder, bowel and sexual function. Rehabilitation, including specialist bladder and bowel care, then continues over the following months.

The outlook depends heavily on the severity and duration of the nerve compression before it is relieved. Leg pain and weakness often improve after decompression, but bladder, bowel and sexual function can be slower and less complete to recover, which is exactly why prompt treatment is so important. Some people regain full function; others are left with lasting difficulties that are managed with specialist support. Ongoing rehabilitation and continence care are central to living well after the injury.

Lasting bladder, bowel and sexual dysfunction are the most significant potential consequences and are the reason the condition is treated so urgently. As with other spinal injuries, care also includes preventing pressure sores, blood clots and infections, and managing nerve-related (neuropathic) pain in the legs. A specialist team supports recovery and long-term adaptation.

Myth: "Back pain with leg symptoms can always wait to be seen." Fact: Saddle numbness, bladder or bowel changes and new leg weakness are emergency warning signs that need urgent assessment.

Myth: "If the legs are working, the nerves are fine." Fact: Bladder, bowel and saddle symptoms can occur even with reasonable leg strength and are the crucial warning signs.

Myth: "Once bladder control is lost it always comes back after surgery." Fact: Bladder and bowel recovery is often incomplete, which is exactly why prompt decompression is so important.

This page is for general education and does not replace an individual assessment. Treatment depends on a person's specific symptoms, examination findings, imaging findings and overall health, and should always be discussed with a suitably qualified healthcare professional.

Below the point where the spinal cord ends, the spinal canal contains a bundle of nerve roots that fan out to supply the legs, the pelvic organs and the saddle area. Because this bundle resembles a horse's tail, it is called the cauda equina (Latin for "horse's tail"). Cauda equina syndrome occurs when these nerve roots are compressed. It is most commonly caused by a large disc prolapse, but it can also be caused by trauma — this page focuses on the traumatic form, which typically follows a fracture of the lower spine. Cauda equina syndrome is regarded as a surgical emergency, because delayed treatment can lead to permanent loss of bladder, bowel and sexual function. This page explains the warning signs, how the diagnosis is made, and what treatment involves.

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• —National Institute for Health and Care Excellence (NICE). Spinal injury: assessment and initial management. NICE guideline NG41. 2016.
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• —Guideline note: NICE NG41 reviewed for initial assessment. British Association of Spine Surgeons (BASS) / Society of British Neurological Surgeons standards of care for cauda equina syndrome informed the emergency-management principles. AO Spine thoracolumbar classification informs injury description. No stand-alone AAOS clinical practice guideline specific to traumatic cauda equina syndrome was identified at the time of writing.

This information is for general patient education and is not a substitute for an individual consultation. Always seek personalised advice from a qualified spinal specialist.