Caused by compression of the nerve roots caudal to the level of spinal cord termination

Aetiology

• Most common cause is compression arising from large central lumbar disc herniation at the L4/L5 and L5/S1 level

Clinical features

Symptoms

• Classically bilateral leg pain, can be unilateral or with no leg symptoms
• Loss of motor or sensory function of bowel/bladder
  • Loss of control/awareness (NOT constipation or increased urinary frequency)
• Perineal/saddle anaesthesia
• Widespread or progressive motor weakness in the legs or gait distribution

Signs

• PR exam - loss of anal sphincter tone

Investigations

• Urgent MRI: to determine level of prolapse

Management

• Urgent discectomy

Complications

• Prolonged compression can cause permanent nerve damage requiring colostomy and urinary diversion
• Even with prompt surgical intervention, significant number of patients have residual nerve injury with permanent bladder and bowel dysfunction