Regarding the natural history of untreated vertebral TB (Pott's disease), the 'cold abscess' formation characteristic of spinal TB is due to:

• A Pyogenic infection with excess neutrophil recruitment creating hot pus
• B Viral infection producing serous exudate
• C Spinal cord ischaemia causing cord oedema
• D Caseation necrosis with liquefaction of the intervertebral disc and adjacent vertebral bodies; the abscess lacks acute inflammatory heat/tenderness because it is paucicellular (macrophage/lymphocyte predominant) without significant neutrophils ✓

Explanation

The term 'cold abscess' distinguishes TB abscesses from pyogenic abscesses. In spinal TB, Mycobacterium tuberculosis causes caseation necrosis (cheese-like central necrosis) of the disc and adjacent vertebral bodies. As the caseous material liquefies it collects under the anterior longitudinal ligament or tracks via fascial planes (psoas, paraspinal muscles). The inflammatory reaction is dominated by granulomas (macrophages, Langerhans giant cells, lymphocytes) rather than neutrophils, so the classic features of acute pyogenic inflammation — heat, redness, local tenderness — are absent, giving the 'cold' quality. The abscess can track long distances (e.g., from L1 to the inguinal region via the psoas sheath) because pressure is low without the acute hyperaemia of pyogenic infection.

Reference: Maheshwari Essential Orthopaedics, 6th ed.

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Written and medically reviewed by the StethoPrep medical team.