Cauda Equina Syndrome: Explained
Cauda equina syndrome (CES) is a neurological condition caused by compression of the cauda equina (Latin for “horse’s tail”); a bundle of spinal nerves and spinal nerve roots which originate in the conus medullaris of the spinal cord (1, 4). CES is most commonly described as a combination of sensory loss of the saddle area, muscular dysfunction and/or loss of reflexes of the lower limbs, urination dysfunction, defecation complaints, and/or sexual dysfunction (1).
Acute onset of the Cauda Equina Syndrome is a medical emergency and missed diagnosis can have devastating consequences – resulting in permanent loss of bowel, bladder, sexual and lower limb function (2). Cauda Equina Syndrome was first described in the literature in 1934 – in which a combination of neurological and urological complaints in patients with a ruptured intervertebral disc where identified (1). Despite the seriousness of the condition, a uni-vocal definition for CES does not exist (1).
The most common documented cause of Cauda Equina Syndrome is herniation, prolapse or sequestration of the lumbar vertebral disc/s (45% of cases) (1,4). Additional, less common causes of the condition are listed below:
- Spinal Stenosis
- Epidural Haematoma
- Primary and metastatic neoplasms (tumours)
- Ankylosing Spondylitis
The Cauda Equina (as mentioned above) is a bundle of spinal nerves and spinal nerve roots which originate in the conus medullaris of the spinal cord (1, 4). The nerves that comprise the cauda equina innervate the pelvic organs and legs to include motor (‘muscle’) innervation of the hips, knees, ankles, feet, and pelvic floor. In addition, the cauda equina extends to sensory innervation of the perineum (‘saddle area’) and, partially, parasympathetic innervation of the bladder.
The traditional tetrad of signs/symptoms for Cauda Equina Syndrome are:
- Saddle Area Sensation Changes (“Perineal Paraesthesia”)
- Numbness or “pins-and-needles” sensations of the groin and inner thighs which would contact a saddle when riding a horse (4)
- This is a larger area than a typical bicycle saddle and includes the genitals, perineum, inner thighs and part of the buttocks. (2)
- Arguably the most common symptom in cases of confirmed CES (2)
- Bladder/Urination Dysfunction
- Overflow incontinence (1,3)
- Urinary retention/lack of awareness of needing to void (1)
- Bowel/ Defaecation Dysfunction
- Defecation symptoms are more common in women than men (1)
- One study reported only 47.1% of those with CES having a defaecation dysfunction at initial pre-sensation. (2)
- In the early stages, the patient may complain of constipation secondary to the loss of parasympathetic innervation to the descending colon, while simultaneously anal tone may be lax (2)
- Faecal incontinence generally occurs late in CES and its absence should not be considered reassuring (2)
- Sexual organ dysfunction
- Sexual dysfunction entails any problem that interferes with any of the normal phases of the sexual activity, these being; sexual interest or libido, sexual arousal, orgasm and resolution (2)
- More specifically in CES – symptoms can include:
- Impotence, decreased potency, difficulties to obtaining orgasm, less intense orgasm, anorgasmy, reduced or absent penile/vaginal sensation, incontinence during intercourse, dyspareunia, absent bulbocavernosus reflex and general reports of abnormal intercourse (2)
Previously it was thought that when the symptoms listed above occur together/individually in combination with back pain – a person is likely to have Cauda Equina Syndrome (1). However, diagnosis of CES can be more complex, as many of the symptoms listed above can occur due to numerous other unrelated conditions/causes (1,3).
In a retrospective review of 753 consecutive patients with lower back pain in the United Kingdom, 14% of LBP patients reported numbness in the gluteal area, 28% reported to have altered bladder and bowel function and 27% felt that their bladder and bowel control had changed with the onset of their LBP – only one had radiologically confirmed Cauda Equina Syndrome (2).
The progression of Cauda Equina Syndrome can be divided into 3 stages, as listed below with their accompanying signs/symptoms:
- Early (CES-E)
- Altered saddle area sensation
- Sciatica symptoms in one or both legs +/- weakness (4)
- Incomplete (CES-I)
- Sciatica symptoms in one or both legs
- One-sided or patchy saddle area numbness
- Altered urinary sensation
- Loss of desire to void
- Needing to strain on urinating
- Increased frequency and urgency of micturition (2,3)
- Complete (CES-R)
- No leg pain or sciatica in one or both legs
- Numbness/abnormal sensation in saddle region
- May have deficit in sensation &/or muscle use in one or both legs
- Painless urinary retention/lack of awareness of needing to void
- overflow incontinence,
- faecal incontinence,
- difficulties attaining a consistent erection and weak, or loss of ejaculation (1,3)
Cauda Equina Syndrome is a highly variable/heterogenous condition – as it presents differently from person to person and progresses slowly – thus making it challenging to promptly diagnose (1,3,5). The gold standard for diagnosis of CES is evidence of compression on MRI in combination with symptoms (1). If not recognised and left untreated, CES can lead to permanent loss of bowel and bladder control, sexual dysfunction or even paralysis (3).
With the recent description of the new third stage of CES – Early (CES-E), it has been suggested that instead of waiting for the onset of pelvic sphincter function abnormalities, Cauda Equina Syndrome should be considered as soon as CES-E symptoms manifest, specifically when symptoms progress from one leg to both (unilateral to bilateral). Patients with CES-I, especially if the history is less than a few days, usually require emergency MRI to confirm the diagnosis followed by prompt decompression surgery (4). It is well established that the outcome for patients with CES-I at the time of surgery is generally favourable, with many regaining full bowel/bladder/sexual functions that were lost (4).
Whereas those who have deteriorated to complete compression of the Cauda Equina (CES-R) have a poorer prognosis (4). The urgency of surgery in CES-R is still not clear however, early decompression removes the mechanical factors which can cause progressive neurological damage (4).
Oliver Crossley (APAM)
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- Korse, N. S., J. A. Pijpers, E. van Zwet, H. W. Elzevier, and C. L. A. Vleggeert-Lankamp. “Cauda Equina Syndrome: presentation, outcome, and predictors with focus on micturition, defecation, and sexual dysfunction.” European Spine Journal26, no. 3 (2017): 894-904
- Woods, Emma, Sue Greenhalgh, and James Selfe. “Cauda Equina Syndrome and the challenge of diagnosis for physiotherapists: A review.” Physiotherapy Practice and Research36, no. 2 (2015): 81-86
- Greenhalgh, S., C. Truman, V. Webster, and J. Selfe. “An investigation into the patient experience of Cauda Equina Syndrome: a qualitative study.” Physiotherapy Practice and Research36, no. 1 (2015): 23-31.
- Curley, A. E., C. Kelleher, C. P. Shortt, and P. J. Kiely. “Cauda Equina Syndrome: A case study and review of the literature.” Physiotherapy Practice and Research37, no. 2 (2016): 111-117.
- Sun, Jing-Chuan, Tao Xu, Ke-Fu Chen, Wei Qian, Kun Liu, Jian-Gang Shi, Wen Yuan, and Lian-Shun Jia. “Assessment of cauda equina syndrome progression pattern to improve diagnosis.” Spine39, no. 7 (2014): 596-602.