What is the treatment and cause of a herniated disc (slip disc) and sciatica?

Understanding Herniated Disc (Slip Disc) and Sciatica

What Causes a Herniated Disc and Sciatica

A herniated disc occurs when the soft inner nucleus of an intervertebral disc pushes through its outer fibrous covering, and sciatica is the leg pain that results when this herniated disc compresses a nerve root—they are directly related conditions, with disc herniation being the cause and sciatica being the primary symptom. 1

The Mechanical Cause

• Disc degeneration is the most common underlying cause of herniation, with the disc's outer covering weakening over time and allowing the inner material to protrude 2
• Risk factors that accelerate disc degeneration include genetics, obesity, occupational factors (especially heavy lifting), smoking, and paradoxically, predominantly sedentary work 2
• More than 90% of symptomatic disc herniations occur at the L4/L5 and L5/S1 levels because these lower lumbar segments bear the most mechanical stress 1

How Sciatica Develops

• Sciatica is pain radiating down the leg below the knee in the distribution of the sciatic nerve, caused by mechanical compression or inflammation of the nerve root from the herniated disc 1
• The compressed nerve root produces characteristic symptoms: back pain combined with leg pain that follows a specific nerve distribution (dermatomal pattern) 1
• Sciatica is the most common symptom of lumbar radiculopathy (nerve root dysfunction) 1

Clinical Presentation and Diagnosis

Key Symptoms to Identify

• The hallmark is lower limb pain radiating below the knee and into the foot and toes, not just back pain alone 3
• Neurological symptoms follow specific patterns based on which nerve root is compressed:
  • L4 nerve root: knee weakness and diminished knee reflexes 1
  • L5 nerve root: weakness in great toe and foot dorsiflexion (lifting the foot up) 1
  • S1 nerve root: weakness in foot plantarflexion (pushing down) and diminished ankle reflexes 1

Physical Examination Findings

• The straight-leg-raise test has 91% sensitivity for herniated disc: reproduction of the patient's leg pain when the leg is raised between 30-70 degrees while lying down 1, 4
• The crossed straight-leg-raise test is more specific (88%) but less sensitive (29%): pain in the affected leg when the opposite leg is raised 1, 4
• A focused neurological examination assessing strength, reflexes, and sensory distribution in the specific nerve root patterns is essential 1

Red Flags Requiring Emergency Evaluation

• Urinary retention has 90% sensitivity for cauda equina syndrome, which requires immediate surgical decompression to prevent permanent neurological damage 1, 5, 4
• Progressive motor deficits at multiple levels, fecal incontinence, or bladder dysfunction indicate cauda equina syndrome 1
• Delaying surgical consultation for cauda equina syndrome results in permanent neurological damage 5, 4

Treatment Approach

Initial Conservative Management (First-Line for All Patients Without Red Flags)

Conservative management should be the initial treatment for at least 4-6 weeks, as most disc herniations improve with noninvasive treatment. 5

• Physical therapy focusing on core strengthening and flexibility exercises is the cornerstone of treatment and should be initiated immediately 5, 6
• Remaining active is more effective than bed rest for acute or subacute low back pain 5
• Most lumbar disc herniations with radiculopathy improve within the first 4 weeks with conservative management 5
• The natural course of acute sciatica is generally favorable, with most pain and disability improving within 2-4 weeks with or without specific treatment 3

When to Order Imaging

• Imaging should be reserved for patients who are potential candidates for surgery or epidural steroid injection after failed conservative therapy 5
• Do not order imaging before completing at least 4-6 weeks of conservative therapy unless red flags are present 5, 4
• MRI is the preferred imaging modality when indicated, as it visualizes soft tissues better than CT without radiation exposure 3
• A critical pitfall: over-reliance on imaging without clinical correlation leads to unnecessary surgical intervention, as disc abnormalities are common in asymptomatic individuals 5, 4

Progression to Advanced Treatment

For persistent symptoms after 6 months of comprehensive conservative therapy, consider epidural steroid injections or surgical consultation. 5

• Epidural steroids may provide short-term relief for persistent radicular symptoms despite conservative therapy lasting at least 6 months 5, 7
• Surgery should be considered only when: 5, 6
  • Nonoperative treatments fail after at least 6 months of comprehensive conservative therapy
  • Progressive neurological deficits are present
  • Cauda equina syndrome develops
  • Severe, disabling pain persists despite conservative management

Surgical Considerations

• Discectomy (surgical removal of the herniated disc) may improve symptoms more quickly than continued conservative management when imaging confirms a herniation correlating with clinical findings 7
• Lumbar spinal fusion is NOT recommended as routine treatment following discectomy for isolated herniated discs causing radiculopathy 5, 4, 6
• Fusion should only be considered in specific circumstances: significant chronic axial back pain, manual labor occupations, severe degenerative changes, or instability associated with radiculopathy 5, 6
• Adding fusion during routine discectomy increases complexity and complications without improving outcomes 4, 6

Prognosis and Outcomes

• Most patients with sciatica from disc herniation improve over 6 weeks with conservative management 7
• There is no difference in outcomes between surgical and conservative treatment after 2 years, highlighting that surgery provides faster relief but not better long-term results 5, 7
• Patient preference is an important factor in clinical management, as currently available evidence does not show any intervention to have clearly superior long-term outcomes 3

Critical Pitfalls to Avoid

• Do not perform premature surgical intervention as initial management unless red flags are present 5, 4
• Do not delay surgical consultation if urinary retention develops, as this indicates cauda equina syndrome requiring emergency decompression 5, 4
• Do not assume imaging findings correlate with symptoms without clinical confirmation, as disc abnormalities are extremely common in people without any symptoms 5, 4
• Do not prescribe bed rest—staying active produces better outcomes 5