What causes cauda equina syndrome?

The cauda equina is a bundle of nerve roots below the spinal cord. These nerves help control sensation and movement in the legs and contribute to bladder, bowel and sexual function. A disc can bulge or rupture into the spinal canal and press on several roots at once. Spinal stenosis can leave too little space around the nerves, and a sudden change may create marked compression.

Less common causes include a growth, infection, bleeding around the spine, inflammation, or an injury that narrows the canal. The cause cannot be identified reliably from back pain alone; clinicians use the symptom pattern and urgent imaging when cauda equina syndrome is suspected.

Treat new bladder or bowel changes, numbness around the saddle area, or worsening weakness in both legs as an emergency. Do not wait for a routine physiotherapy appointment or try to manage these signs with exercises at home. Go to an emergency department or contact local emergency services, and explain that cauda equina syndrome is a concern. Take a list of medicines and describe when each symptom began.

Seek emergency assessment immediately for difficulty starting urine, inability to control urine or stool, reduced sensation when wiping, numbness in the groin or inner thighs, or rapidly increasing leg weakness. Severe back pain with these changes is especially concerning, but pain does not have to be severe for urgent assessment to be needed. A clinician may check leg strength, reflexes and sensation before arranging imaging and specialist review.

Ask which finding is causing the nerve compression, whether urgent imaging is needed, and which changes should prompt an immediate return to emergency care. You can also ask how the suspected cause affects treatment and whether any medicines, injections or procedures should be avoided until the nerves have been assessed.