A 35-year-old woman has 4 months of low back pain with evening fever. MRI shows destruction of two adjacent thoracic vertebral bodies with a large paravertebral collection, while the intervertebral disc height is largely preserved. Which feature best explains the preserved disc?

• A The disc is protected by the anterior longitudinal ligament
• B Tubercle bacilli lack the proteolytic enzymes required to destroy the avascular disc cartilage early ✓
• C Paravertebral abscess decompresses the disc space
• D Disc destruction occurs only after neurological deficit appears

Explanation

Mycobacterium tuberculosis produces no proteolytic enzymes, so it spreads beneath the anterior longitudinal ligament and destroys vertebral bodies and adjacent discs only slowly and by extension, unlike pyogenic spondylodiscitis where rapid disc destruction is characteristic. Disc narrowing in spinal tuberculosis is a relatively late sign, and its preservation on MRI supports a tuberculous aetiology over a pyogenic one.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.