Posterior and Lateral Disc Protrusion: Anatomy, Symptoms, and Treatment

A broad-based posterior and lateral disc protrusion (often called a "broad-based disc bulge" or "focal protrusion extending posterolaterally") is a common MRI finding describing disc material extending beyond the vertebral body margin into the spinal canal and/or neural foramen.

Anatomy

• Disc: Annulus fibrosus (concentric lamellae) encases nucleus pulposus (gelatinous, high water).
• Protrusion: Nucleus pushes through annular fissures but outer annulus/ligament remains intact (vs. extrusion: complete annular tear; sequestration: fragment free).
• Posterolateral Location: Most common (annulus thinnest, posterior longitudinal ligament narrowest). Encroaches on:

1. Spinal Canal: Central stenosis → myelopathy (cord compression) or cauda equina syndrome (rare, surgical emergency).
2. Lateral Recess / Neural Foramen: Nerve root compression → radiculopathy (sciatica in lumbar, radiculopathy in cervical).

Symptoms (Depend on Level & Severity)

• Radiculopathy: Dermatomal pain, paresthesia, weakness, reflex loss. L4-L5 → L5 root (foot drop, lateral leg numbness). L5-S1 → S1 root (plantar flexion weakness, lateral foot numbness).
• Axial Back/Neck Pain: Discogenic (annular tear, chemical irritation).
• Myelopathy (Cervical/Thoracic): Gait imbalance, hand clumsiness, hyperreflexia, Babinski, bowel/bladder changes.

Treatment Algorithm

1. Conservative (6–12 weeks): NSAIDs, activity modification (avoid flexion/rotation), PT (McKenzie extension, core stabilization), epidural steroid injection (radiculopathy).
2. Indications for Surgery: Progressive neurologic deficit, cauda equina syndrome, intractable pain >6–12 weeks conservative, myelopathy. Microdiscectomy / laminectomy / foraminotomy.
3. Emerging: Biologic (PRP, stem cells), annuloplasty, endoscopic discectomy.

Key: Many asymptomatic adults have disc protrusions on MRI. Treat the patient, not the image. Clinical correlation essential.