Cauda equina syndrome

The cauda equina (Latin: "horse's tail") is the bundle of nerve roots that descend from the end of the spinal cord through the lumbosacral canal. These roots, which resemble a horse's tail, supply motor and sensory function to the legs and control bladder and bowel sphincters. When compression of these roots is severe and sudden, the result is cauda equina syndrome — a neurological emergency.

**Most common cause:** A massive lumbar disc herniation in which the nucleus pulposus ruptures and occupies a large portion of the spinal canal, directly compressing multiple nerve roots simultaneously.

**Other causes:** Spinal tumour, spinal stenosis, vertebral fracture (e.g., from trauma or osteoporosis), spinal haematoma or abscess, or post-surgical complications.

**Symptoms** — the classic presentation includes some or all of: - Severe low back pain - Bladder dysfunction: urinary retention (most common) or incontinence - Bowel incontinence - Muscle weakness or sensory loss in one or both legs - Difficulty walking - Loss or reduction of leg reflexes - Saddle anaesthesia — numbness in the buttocks, perineum, and inner thighs (the areas that would contact a horse's saddle)

Symptoms vary in severity depending on which roots are compressed and to what degree. Early presentation may be incomplete — any suggestion of bladder or bowel involvement in the context of acute back pain requires emergency imaging (MRI).

**Diagnosis:** MRI is the gold standard — it images the spinal cord, nerve roots, discs, and ligaments and identifies the level and cause of compression. CT myelogram is an alternative.

**Treatment:** Cauda equina syndrome is a surgical emergency. Decompression surgery performed within hours of onset gives the best chance of recovery of motor, sensory, and sphincter function. Delayed surgery significantly worsens the prognosis.

Following surgery, bladder function often takes longer to recover than motor function. Intermittent self-catheterisation and medications may be needed. With appropriate rehabilitation, gradual improvement of bladder and sphincter function can continue for years after surgery.