Approach

CES is characterised by low back pain; bladder, bowel, and sexual dysfunction; and pain and sensorimotor loss in the lower limbs. However, presentation varies widely between patients, and many of the early signs and symptoms may be subtle and non-specific. Bladder dysfunction is always apparent at some stage in the progression of CES. It is vital to take a complete history and to thoroughly investigate symptoms and signs.[6][13]

Severe, late CES is associated with poor prognosis and can result in permanent disabilities, including limb paralysis and loss of bladder, bowel, and sexual function. Therefore, early diagnosis and treatment are key, and clinicians need to be aware of the signs and symptoms of patients with early CES as well as the risk factors for developing CES.[7][12]

The following red flags for CES are listed by the American College of Radiology:[14][15]

  • Acute onset of urinary retention or overflow incontinence

  • Loss of anal sphincter tone or faecal incontinence

  • Saddle anaesthesia

  • Bilateral or progressive weakness in the lower limbs.

However, it has been argued that true red flags should be symptoms and signs that warn of further, avoidable damage, and that symptoms and signs of late, irreversible CES are more accurately described as 'white' rather than 'red' flags.[16] The diagnostic accuracy of red flags for serious spinal pathology has been questioned.[8][17][18][19]

Early warning symptoms of CES include: back pain; unilateral leg weakness; fluctuating symptoms followed by onset of bilateral leg numbness or weakness; any alteration in the sensation of a full bladder, urgency, or awareness of passing urine; and onset of any sense of numbness or 'pins and needles' around the anus or genitals.[7][16]

History

Taking a thorough history is critical to the early diagnosis of CES.[13] If a patient reports any symptoms and signs suggestive of CES, the clinician should ask them specifically about symptoms known to be typical of the condition. It has been suggested that non-specialists could use a simple CES 'toolkit' to facilitate the subjective examination of patients presenting with low back pain who are potentially at risk of CES.[20]

Patients typically report low back pain and/or bilateral or unilateral sciatica (leg pain secondary to lumbosacral nerve root pathology). Usually, this has become worse over time, although acute onset of severe pain is not uncommon.

Bladder dysfunction is always present at some stage in the progression of CES.[4][13] Early presentation may be a reported difficulty in starting or stopping the urine stream, urgency, loss of urge to urinate, or reduced awareness of a full bladder or of passing urine. Retention and overflow incontinence are signs of CES that may be irreversible.

Other symptoms and signs of CES that patients may report, and should be asked about, include numbness and leg weakness, bowel dysfunction (e.g., loss of sensation of rectal fullness, faecal incontinence, laxity of the anal sphincter), and sexual dysfunction (e.g., reduced sensation, erectile dysfunction). Not all patients show all symptoms, and symptom onset may be acute or insidious.[4][5][6] Later presentations may involve saddle anaesthesia (i.e., loss of sensation in the area of the perineum, buttocks, and posteromedial thighs).

The concept of 'grumbling' CES is most notable in patients with spinal bone abnormalities (i.e., scoliosis, lumbar stenosis, post-fusion surgery), and the signs and symptoms can be confused with the primary spinal problem.[5][21][22]

The risk of CES is higher in patients on anticoagulation therapy and following spinal surgery, so a high index of suspicion of CES is appropriate for these patients when presenting with back or leg pain.[4]

British Association of Spine Surgeons guidelines recommend that any patient presenting with low back pain and/or sciatic pain should be suspected of having threatened, or actual, CES if they also have any of the following: disturbance of bladder or bowel function, saddle or genital sensory disturbance, or bilateral leg pain.[23][24] It should be noted that some degree of urinary dysfunction may be associated with pain inhibition or drugs such as opioids, but neither pain inhibition nor drugs cause reduced urethral or bladder sensation.

Exam

Detailed exam of the lumbar and sacral nerve roots should be carried out, including testing sensation to pinprick in the perianal region, perineum, and posterior thigh. The anal wink (anal reflex) should be tested, although it has relatively low sensitivity and specificity for diagnosing CES.[1][7] An absent anal wink suggests sacral nerve root dysfunction.[25] Loss or diminution of the bulbocavernosus reflex has also been suggested to be indicative of CES, but sensitivity and specificity are low, and it may not always be appropriate.[26][25]

A digital rectal examination may be carried out to assess for tone/presence of voluntary anal contraction. Although the value of digital rectal examination in the acute diagnosis of CES has been questioned, it may provide additional information, be helpful in determining the severity of injury, and help guide bowel and bladder programmes.[27][28] Clinicians must assess for contraindications (e.g., immunocompromised state, recent anal surgical intervention) before performing the examination.[29]

A full bladder due to urinary retention may be revealed on palpation.

Imaging

It is essential that imaging is carried out as soon as possible in patients with suspected CES, to ensure minimal delay if decompression surgery is needed.[6]

Magnetic resonance imaging (MRI)

MRI of the lumbar spine without gadolinium enhancement is the preferred imaging investigation.[4][15] MRI can identify space-occupying lesions in the spinal canal and compression on neural structures. Use of gadolinium enhancement may be used to investigate the aetiology of CES when underlying malignancy, infection, or inflammation is suspected.[15]

There can be a discrepancy between the physical examination and MRI.[30] The sensitivity of basic MRI, as it relates to CES, is one of 'ruling in', rather than 'ruling out', and any single test needs to be integrated into the full clinical picture.

Computed tomography (CT)

CT should be carried out only if MRI is unavailable or contraindicated. CT myelography can be used to assess the patency of the spinal canal/thecal sac, and can be useful for surgical planning.[15] Relative CT criteria for diagnosing CES (if MRI is unavailable) have been defined.[31]

Other investigations

Other investigations may provide useful additional information, but must not delay MRI scanning (if there is clinical suspicion of CES) or surgery.

Urodynamic testing can be used to evaluate the degree and cause of sphincter dysfunction.[4][32] However, it may not be practical in an emergency setting, and must not delay surgery.

Retention and completeness of bladder emptying can be assessed using ultrasound.[33] In one study, a postvoid residual volume of >200 mL was associated with a 43.0% probability of having CES, compared with a probability of 3.6% for patients with a postvoid residual volume of <200 mL.[34] However, although a postvoid residual volume of <200 mL reduces the probability of CES, it does not exclude it.[35]

Urodynamic testing may also be useful for monitoring recovery of bladder function after decompression surgery.

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