Intervertebral disc herniation occurs when nucleus pulposus material protrudes through defects in the annulus fibrosus, potentially compressing adjacent neural structures. It is a key manifestation of degenerative disc disease and a common cause of radicular symptoms.

Disc Structure and Failure

The disc’s nucleus pulposus is rich in proteoglycans and water, providing hydrostatic support, while the annulus fibrosus consists of concentric collagen lamellae. Degeneration leads to:

• Loss of water content and height in the nucleus.
• Fissuring and weakening of the annulus, especially posterolaterally.
• Reduced ability to distribute mechanical load.

When intradiscal pressure increases (flexion, axial load), nucleus material can migrate toward weakened areas, forming protrusions, extrusions or sequestrations.

Neural Compression and Inflammation

Herniation can narrow the intervertebral foramen or spinal canal, compressing:

• Nerve roots, causing radicular pain, sensory changes and weakness in the corresponding dermatome/myotome.
• Less commonly, the spinal cord (cervical, thoracic) or cauda equina (massive lumbar herniations).

Besides mechanical compression, inflammatory mediators from nucleus material (e.g. phospholipase A₂, cytokines) sensitize nerve roots and contribute to pain even with modest compression.

Clinical Patterns

• Cervical hernias may produce neck pain with radiation into the arm, paresthesias and segmental weakness.
• Lumbar hernias commonly cause sciatica: pain radiating down the leg, often with positive straight leg raise.
• Red flag signs (progressive weakness, saddle anesthesia, bladder/bowel dysfunction) suggest serious compromise and demand urgent evaluation.

Natural Course and Treatment

Many herniations show spontaneous regression over months as extruded material dehydrates and is resorbed by macrophages. Management strategies include:

• Conservative: analgesics, NSAIDs, short-term rest, early mobilization, physical therapy and education about safe movement.
• Interventional: epidural steroid injections in selected cases.
• Surgical: microdiscectomy or decompression when pain is refractory or neurological deficits progress.

Disc herniation illustrates how structural disc failure, mechanical forces and inflammation converge on neural tissue. Understanding this interplay supports balanced decisions between conservative and surgical options.