The spine is the most common site of skeletal tuberculosis accounts for 50 percent of the cases. Lower thoracic region is the most common segment involved followed by lumbar, upper dorsal, cervical and sacral regionsin decreasing order of frequency.
In the past, tuberculous spondylitis used to be a disease of early childhood. But with improved public health measures, this age incidence has changed, and adults are more frequently affected.
Focus of infection usually begins in the cancellous bone of the vertebral body. Occasionally it is in the posterior neural arch, transverse process, or subperiosteally deep to the anterior longitudinal ligament in front of the vertebral body.
Occasionally there may be multiple foci of involvement separated by normal vertebrae termed as skip lesions, or the infection may be disseminated to distant vertebrae via the paravertebral abscess.
The vertebral bodies loose their mechanical strength as a result of progressive destruction under the force of body weight and eventually collapse with the intervertebral joints and the posterior neural arch intact; thus, an angular kyphotic deformity is produced, the severity of which depends upon the extent of destruction, the level of the lesion, and the number of vertebrae involved.
Kyphosis is most marked in thoraccic area because of the normal dorsal curvature. In the lumbar area it is less because of the normal lumbar lordosisbecasue of which the body weight is transmitted posteriorly and collapse is partial
The collapse is minimal in cervical spine because most of the body weight is borne through the articular processes.
Healing takes place by gradual fibrosis and calcification of the granulmatous tuberculous tissue. Eventually the fibrous tissue is ossified, with resulting bony ankylosis of the collapsed vertebrae.
Paravertebral abscess formation occurs in almost every case. With collapse of the vertebral body, tuberculous granulation tissue, caseous matter, and necrotic bone and bone marrow are extruded through the bony cortex and accumulate beneath the anterior longitudinal ligament.
These cold abscesses gravitate along the fascial planes andpresent externally at some distance from tee site of the original lesion.
- In the lumbar region the abscess gravitates along the psoas fascial sheath and usually points into the groin just below the inguinal ligament.
- In the thoracic region, the longitudinal ligaments limit the abscess, which is seen in the radiogram as a fusiform radiopaque shadow at or just below the level of the involved vertebra.
- Thoracic abscess may reach the anterior chest wall in the parasternal area by tracking via the intercostal vessels.
Compression of the cord by the abscess or by the caseating or granulating mass, or by the posteriorly protruding border of the intervertebral disc or edge of bone can result into neural deficit. Other contributory factors may be thrombosis of the local vessels and edema of the cord.
Neural deficit can be paraparesis to begin with and eventually lead to paraplegia. It occurs most often in the mid-or upper-thoracic region, where the kyphosis is most acute, the spinal canal is narrow, and the spinal cord is relatively large.
The onset of is usually insidious and of slow evolution. Initial symptoms are vague, consisting of generalized malaise, easy fatiguability, loss of appetite and weight, and loss of desire to play outdoors. There may be an afternoon or evening fever.
Backache is usually minimal and may be referred segmentally.
Muscle spasm makes the back rigid. Motion of the spine is limited in all direction.
When picking an object up from the floor, the patient flexes his hips and knees, keeping the spine in extension.
Spasm of the paravertebral muscles in the lumbar region is also elicited by passive hyperextension of the hips with the patient in prone position-this also puts stretch on the iliopsoas muscle, which is in spasm and contracture owing to psoas abscess.
A kyphus in the thoracic region may be the first noticeable sign. As the kyphosis increases, the ribs will crowd together and a barrel chest deformity will develop.
When the lesion is situated in the cervical or lumbar spine, a flattening of the normal lordosis is the initial finding.
On gentle percussion or pressure over the spinous process of the affected vertebrae, tenderness is often present. The abscesses may be palpated as fluctuant swellings in the groin, iliac fossa, retropharynx, or on the side of the neck, depending upon the level of the lesion.
The gait of the person with Pott’s disease is peculiar, reflecting the protective rigidity of the spine. His steps are short, as he is trying to avoid any jarring of his back. In tuberculosis of the cervical spine, he holds his neck is extension and supports his head with one hand under the chin and the other over the occiput.
If paraplegia develops, there will be spasticity of the lower limbs with hyperactive deep tendon reflexes, a spastic gait, a varying degree of motor weakness, and disturbances of bladder and anorectal function.
Findings are suggestive, but not pathognomonic. In addition to the routine anteroposterior and lateral views of the spine, linear tomograms, CAT scan, and nuclear magnetic resonance imaging are used to delineate bone and spinal cord pathology in detail. Chest radiograms and an intravenous pyelogram are taken to rule out outer foci of systemic disease in case of a suspected person.
The vertebral body depicts the initial changes; it becomes rarefied with loss and haziness of its bone trabecular pattern. Soon the vertebral body expands and its borders are indistinct. With progressive destruction of bone the vertebral body collapses. The intervertebral disc space first narrows and later is obliterated. Paraspinal abscesses may be seen quite early, presenting as fusiform or rounded shadows of water density.
In the differential diagnosis one should consider
- Suppurative spondylitis
- Hodgkin’s disease
- Eosinophilic granuloma
- Aneurismal bone cyst
- Ewing’s sarcoma.
All these conditions may causes destruction and collapse of the vertebral body, narrowing and obliteration of intervertebral disc spaces, and paraspinal soft-tissue swelling, a picture also seen in tuberculosis.
As soon as the diagnosis of tuberculous spondylitis is suspected, the patient is placed on bed rest and chemotherapy is initiated immediately. Patient is observed for response of the disease. A number of patients recover on chemotherapy.
Some of the patient may require surgical debridement or decompression of the cord
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