| Clinical Profile |
| Findings |
| Discussion |
| Pathogenesis |
| On MRI |
| Differential Diagnosis |
| Suggested Reading |
 |
H/O backache and radicular pain in BLE since 8 to 9 months. Patient has pulmonary tuberculosis.
The L1, L2 and L3 vertebral bodies show hypointense areas on the T1W
images and these turn hyperintense on the T2W images. The L1-L2 and L2-L3 intervertebral
discs are also involved. There is an anterior epidural lesion at the L2 and L3 vertebral
levels. It is hypointense with a hyperintense rim on the T1W images and hyperintense with
a hypointense rim on the T2W images. This would be suggestive of an abscess. Slight
prevertebral soft tissue extension is noted. The psoas muscles are bulky bilaterally and
show presence of abscesses. A similar lesion is noted within the left paraspinal muscles.
Usually have an indolent course with low grade fever, weight loss and progressively increasing backache. They may also have radicular pain, sensory impairment, paraparesis or paraplegia and kyphotic deformities. Predisposing conditions may be AIDS, immunosuppression and malnutrition. Patients may have pulmonary tuberculosis.
The offending organism is the Mycobacterium tuberculosis bacillus. The organism usually
involves the anterior subchondral space of the vertebral body (hematogenous spread). It
tends to spread contiguously and may involve the disc and subsequently the adjacent
vertebral body. The disc may be spared and the infection may track into the subligamentous
space and adjacent soft tissues. Paravertebral abscesses may calcify. Solitary vertebral
involvement is rare. Posterior elements may be involved. The dorso-lumbar region is
commonly afflicted. Occasionally may present as a soft tissue abnormality with little or
no bone or disc involvement.
On healing, fatty changes and sclerotic changes are noted. The disc may show ankylosis.
Inadequate treatment may cause vertebral collapse with gibbus formation.
There is replacement of the normal marrow by inflammatory tissue (with
hyperemia, edema and pus) and this is usually hypointense on the T1W images and turns
hyperintense on the T2W images. It may be found in the subchondral region or may be seen
as a more diffuse involvement. The sagittal images may show it to be a disc centered
process. Contrast enhancement is useful in those who have an inhomogeneous marrow pattern
and is of marginal value in those with fatty vertebral marrow. Fat saturation techniques
help. Typically the hyperemic and osteomyelitic bone enhances.
Skip lesions may be seen with multivertebral involvement and relative sparing of the
intervertebral discs. Involvement of the posterior elements is fairly common.
In people over thirty years an intranuclear cleft (hypointense linear signal on the T2W images) is noted within the centre of the disc. The loss of this cleft on T2W images may suggest early discitis (especially when the cleft is well visualized within the other discs). The disc may be decreased in height and hyperintense on the T2W images. Occasionally an enlarged edematous disc may be encountered. Adjacent marrow signal changes and erosion of the cortical endplates may be seen. The involved disc has a very variable pattern of enhancement. Initially thin central linear or thick focal enhancement conforming to the signal alteration on the T2W images may be seen. Thin or thick marginal disc enhancement may be noted. Occasionally the disc enhances inspite of there being no signal alteration.
Tuberculosis tends to involve the soft tissues commonly with abscess
formation. Large paravertebral or psoas abscesses (calcifications may be seen) are
commonly involved. These may be out of proportion to the degree of involvement of the
vertebra or disc. Abscesses may also be seen in the paraspinal region and epidural space.
The abscesses are usually located ventrally in the cervical and lumbar spine and
posteriorly in the dorsal spine. The leptomeninges may be involved. Intraosseus abscesses
may be seen.
The abscesses are invariably seen to have a centre which is isointense to hypointense to
normal muscle with a slightly hyperintense rim on the T1W images. On the T2W images the
centre is hyperintense and the rim hypointense. Contrast enhancement of the rim is noted.
These lesions usually yield drainable pus. It may be difficult to distinguish phlegmon
(inflammatory mass of granulation tissue) from an abscess. Phlegmon usually shows diffuse
contrast enhancement. This inflammatory tissue may tunnel beneath the paraspinous
ligaments.
The end-stage shows narrowing of the disc space or partial or complete obliteration with fusion of the vertebral bodies. The soft tissue components usually regress. The vertebral body may show central or anterior wedging with gibbus formation. Hyperintense signal on the T1W images may reflect the presence of fatty changes or yellow marrow, the result of healing. Sclerotic changes (hypointense) may be seen.
Pyogenic Spondylitis:
It is difficult at times to distinguish between the two. Pyogenic spondylitis usually involves the lumbar or dorsal spine. Multivertebral involvement is less common whereas the disc is invariably involved. Posterior element involvement is uncommon. Paravertebral abscesses are seen in less than 20%.
Brucellar Spondylitis:
Has a predilection for the lower lumbar spine. The anatomic vertebral architecture stays intact inspite of the signal alteration. The disc is commonly involved. Soft tissue involvement is moderate. May have diffuse or focal forms. The focal form involves the subchondral bone of the L4 or L5 vertebral bodies (antero-superior aspect at the discovertebral junction). Brucella agglutination test may be positive.
Tumours:
When there is multivertebral involvement with sparing of the disc it is difficult to distinguish from neoplasia like metastases or small cell tumours.