The cauda equina syndrome (CES)
Assessment and management in the emergency department
Back pain with or without leg pain (sciatica) is extremely common and because the pain can be excruciating, patients frequently attend the emergency department. The cauda equina syndrome is, by comparison, rare though interestingly it is a condition that is well recognised by a reasonably competent doctor working in the emergency department.
Typically the cauda equina syndrome is caused by a central lumbar disc prolapse which gives rise to back pain and bilateral leg symptoms and possibly signs. What heralds the onset of the cauda equina syndrome is when the patient develops symptoms of bladder, bowel or sexual dysfunction and/or the novel symptom of numbness in the saddle area due to compression of the sacral nerves.
Red flag symptoms include urinary frequency, urine incontinence and the loss of the sensation of actually passing urine. The loss of bladder and urethral sensation may lead to the patient suddenly and unexpectedly wetting themselves. Loss of sensation can also affect the rectum though faecal incontinence is usually a late feature. Constipation is not a feature of the cauda equina syndrome and is commonly seen in patients with severe back pain due to the opioid analgesia that is frequently prescribed to control such symptoms.
The novel symptom of going numb in the saddle area which includes the perianal region, the scrotum and labia should always be taken as an indication that the patient with back pain is developing the CES. The patient may complain of pins and needles, a burning sensation or numbness which they may appreciate for the first time when wiping their bottom.
It is, therefore, essential to enquire of any patient with back pain about bladder, bowel and sexual dysfunction and altered sensation in the saddle area. Enquiring about such red flag symptoms is a mandatory part of the clinical assessment of all patients with back pain.
It is recognised that the cauda equina syndrome gives rise to variable symptoms and signs as it moves from the incomplete syndrome (CESI) to complete syndrome when there is urinary retention (CESR). In CESI the patient may have symptoms but little in the way of clinical signs. Therefore in the presence of red flag symptoms, it would be inappropriate and substandard to discount the possibility of the cauda equina syndrome because the patient had no objective signs.
As the speed of transition from CESI to CESR is very variable but may occur over a few hours, the role of the ED clinician is to refer patients with red flag symptoms even in the absence of signs for urgent investigation with an MRI scan and assessment by the spinal/neurosurgical team.