Back pain

Red flags for cauda equina compression syndrome

  • Saddle or genital anaesthesia or altered sensation (and, after almost getting horribly caught out once, I will at least now remember forever after that THIS MAY PRESENT UNILATERALLY)
  • Altered bladder, bowel, or sexual function
  • Gait disturbance
  • Severe progressive neurological deficit in legs.

Cauda equina compression may present acutely or insidiously; it may also present after a long history of unalarming back pain without neurological signs.


Other red flags for back pain

  • Age <20
  • Age >50 (seriously? That’s a lot of people)
  • Trauma
  • Systemic illness (fever, weight loss)
  • Known cancer or HIV


Spinal stenosis symptoms

  • Unilateral or bilateral leg pain, numbness, and weakness (with or without associated back pain) coming on after walking a particular distance
  • Relieved by forward flexion, exacerbated by extension
  • Typically, patient can walk uphill or ride a bike without difficulty.


Assessment of nerve roots

  • Straight leg raise – tests L4 – S1 nerve roots. (Positive result is reproduction of pain at 30 – 70 degrees. SLR has a sensitivity of 91% for sciatica but a specificity of only 26% – however, crossed SLR has a sensitivity of 29% and a specificity of 88%, so using the two in combination can be of some use.)
  • Knee jerk – L 3 – 4
  • Sensation great toe – L5
  • Extension great toe – L5
  • Sensation litte toe – S1 (the ‘1 supplies 5 and 5 supplies 1’ rule)
  • Standing on tiptoe – S1
  • Ankle jerk – S1


Prognosis of sciatica

About 50% of patients report some improvement within 10 days and about 75% report some improvement within 4 weeks.



Not specifically relevant to back pain, but note that NICE now recommends adding a PPI to NSAID treatment for anyone over 45, as they’re now so cheap it’s automatically cost-effective (not sure whether that takes possible complications of PPIs into account, but, there you go, that’s what the guidance says).


Surgery for sciatica

In one study, this gave short-term improvement (patients were quicker to return to normal activities), but differences were not statistically significant by 6 months and were non-existent by 12 months. It has also been noted (the associated editorial) that surgery helps (in the short term) 90% of radicular pains, but only 30% of back pains, and in 5% of cases it makes the pain worse. Also, neurological damage occurs in 1%.


Random useful tip

Remember that back pain may occasionally be referred pain from other causes, notably including AAA. Think of this one in elderly men and check femoral pulses!


(Pulse on-line learning module – selected as I have a patient with persistent back pain to see tomorrow, and decided it was time to update myself on red flags and management)


About Dr Sarah

I'm a GP with a husband and two young children.
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