- The spine is the most common site of skeletal tuberculous infection and the thoracolumbar region is the most commonly affected region. Tuberculosis of the spine affects the corners of the vertebral bodies, especially the anterior corner. This predilection may reflect tubercular seeding occurring via the paravertebral venous plexus of Batson rather than the more usual route of spinal arteries. Thereafter, tubercular infection spreads anteriorly or posteriorly into the vertebral body or disc. Three patterns of vertebral body involvement are recognized: paradiskal, anterior and central lesions.[1
- Paradiskal infection is adjacent to the disc space. The disc space narrowing is caused either by destruction of subchondral bone with subsequent herniation of the disk into the vertebral body or by direct involvement of the disk.[2] This is the most common pattern of spinal tuberculosis. Any tubercular vertebral lesion, such as anterior or central lesion, which does not have the aforementioned typical radiographic features, is referred to as atypical spinal tuberculosis. The importance of these lesions is that they are rare and difficult to differentiate clinically and radiographically from neoplastic process.
- Anterior lesions are subperisosteal lesions under the anterior longitudinal ligament. Pus spreads over multiple vertebral segments, stripping the periosteum and anterior longitudinal ligament from anterior surface of vertebral bodies. The periosteal stripping renders the vertebrae avascular producing anterior scalloping.[4]
- Central lesions are centered on the vertebral body with disc sparing. Vertebral collapse can occur, producing a vertebral plana appearance. The lesions may be in continuity, affecting from two to four contiguous vertebrae or may affect different levels in different region of spine. Posterior elements of vertebrae are rarely involved in isolation.[2]
The differential diagnosis of tubercular spine includes pyogenic and fungal infections, sarcoidosis, metastasis, and lymphoma. In spinal lesions, involvement of intervertebral discs, presence of paravertebral abscesses/collection and involvement of two contiguous vertebral bodies are suggestive of tuberculosis of spine. In neoplastic involvement of spine, disc spaces are usually spared and paravertebral abscesses are not seen although solid extraosseous soft tissue component may be associated if vertebral bodies are destroyed. Skip or non consecutive multifocal involvement of spine also favors neoplastic lesion. In central and posterior element forms of tuberculosis, only biopsy can provide diagnosis. Therefore, a high index of suspicion is required for spinal tuberculosis even in atypical presentations in areas with high endemicity of this infection.
by Dr.SANZGIRI, GOA MEDICAL COLLEGE
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