POTT’S SPINE TUBERCULOSIS
INTRODUCTION:
Tuberculosis is the ninth leading cause of death worldwide and the leading cause from a single infectious agent,
ranking above HIV/AIDS(As per WHO sources).Tuberculosis is a major cause of concern in developing countries. Spinal tuberculosis,
as one of its manifestations,
too has acquired greater magnitude and has a noticeable presence even in the developed countries.
Spinal tuberculosis accounts for about 2% of all cases of tuberculosis,
15% of the cases of extra pulmonary tuberculosis and 50% of the cases of skeletal tuberculosis.
The organism responsible is Mycobacterium tuberculosis.
The usual root of spread is haematogenous.
The most common clinical features of spinal tuberculosis are backache,
localized tenderness,
stiffness,
spasm of muscles and even spinal deformities.
Plain radiography has been used as the basic primary investigation of choice in developing countries due to its cost effectiveness as well as its easy availability.
But it is usually helpful only in the late stage of the disease.
Newer diagnostic modalities like- CT,
MRI and PET are currently being utilized more frequently and are seen to be replacing plain radiography wherever possible.
MRI is the ideal imaging modality for evaluation of spinal tuberculosis.In addition to the high contrast resolution and multi-planar images,
it also helps in the assessment of spinal cord and neural elements.
Early diagnosis of spinal tuberculosis is of paramount importance as it helps in limiting the bone deformities and complications arising out of cord compression.
AIMS:
The main aim of this study is to illustrate the findings of potts spine on MRI
OBJECTIVES:
MRI has been considered the best imaging modality in evaluation of spinal infection and helps to distinguish between an infection and other clinical conditions
MRI helps in:
1. Early diagnosis of spinal tb
2. Assessment of different patterns of involvement in Pott’s spine .
2. Describing the extent of bony involvement and associated deformity
3. Assessment of collection/abscess (subligamentous,psoas or epidural)
4. Assesssment of involvement of spinal cord /compression of nerves
5. Monitoring the response to therapy and assessment of extent of resolution
PATHOLOGY:
Essentially,
Pott’s spine is secondary infection,
the primary source or site can be traced to lungs or even genito-urinary tract.
The most common mode of spread from primary site to spine is haematogenous.
Tubercular infection reflects characteristic delayed hyper-sensitive immune reaction.
It begins as an inflammatory reaction with Langerhans’ giant cells,
epithelioid cells,
and lymphocytes.
There is proliferation of granulation tissue causing thrombosis of vessels.
There is tissue necrosis along with the breakdown of inflammatory cells which results in an abscess which may remain confined locally or tracks along tissue planes.
Progressive necrosis of bone may ultimately result into bony deformity (kyphosis).
The infection usually initiates from the anterior aspect of the vertebral body closer to the disk.
The infection eventually engulfs adjacent vertebral bodies under the longitudinal ligaments.
Occasionally,
non-contiguous (skip) lesions are also encountered.
SITE:
Thoraco-lumbar junction appears to be the most common site of spinal tuberculosis.
The incidence decreases above and below this level.
However,
any other segment of the spine may also be involved.
PATTERN OF VERTEBRAL INVOLVEMENT:
Three patterns of vertebral body involvement are usually recognized: paradiscal,
anterior,
and central lesions
PARA-DISCAL:
- Most common pattern of spinal tuberculosis.
- A para-discal lesion is adjacent to the inter-vertebral disk leading to narrowing of the disk space.
The disk space narrowing is caused either by-
- Destruction of sub-chondral bone with subsequent herniation of the disk into the vertebral body,
or
- By direct involvement of the disk.
ANTERIOR:
- This is a sub-periosteal lesion under anterior longitudinal ligament.
- The infection/pus spreads over multiple vertebral segments,
resulting in stripping of the periosteum and anterior longitudinal ligament from the anterior surface of the vertebrae.
- The stripping of the periosteum renders the vertebrae avascular and susceptible to infection.
The ischemia and pressure causes anterior scalloping of the vertebrae.
CENTRAL:
- This lesion is in centre of the vertebral body.
- There is vertebral collapse leading to formation of vertebra-plana appearance.
- There is no involvement of the disk.
- The posterior spinal element involvement is rare.
It may involve the pedicle,
lamina or spinous process.
Bone erosion or abscess formation may be present
COMPLICATIONS OF THE DISEASE:
- Paraplegia or paralysis of the lower body is the most serious complication of spinal tuberculosis.Immuno-deficiency contributes to a more rapid progression of the infection.
- Collapse of spinal vertebrae
- Abscesses may spread into adjacent soft tissues,
forming sinuses.
- Spinal cord and nerve compression.