spinalTB

Spinal tuberculosis is common in the developing countries and also seen sporadically in well-developed countries. Lately the incidence is on the increase, world over, with the emergence of AIDS. About 60 % of cases are below the age of 20 years in developing countries. In developed countries the older people are more commonly affected.

About 20% of the patients have multiple lesions.

Most are caused by the human strain. The bovine type is probably responsible for less than 5 %, especially in Europe. Isolated cases due to atypical mycobacteria are also seen.

Pathology:

Microscopically, there is central coagulative necrosis surrounded by epitheloid cells, Langhans giant cells(as shown by the arrow in the picture) and an admixture of lymphocytes and plasma cells. There may be satellite lesions and perivascular infiltrations

Tuberculosis may involve the vertebra, epidural space, dura, arachnoids, or spinal cord.

A) Vertebral involvement:

It is the commonest. It is also the commonest form of skeletal tuberculosis with an incidence of up to 50% of all skeletal tuberculosis. In general it is a disease of the young adult in the developing countries. In developed countries it affects more commonly, the elderly. Due to the emergence of HIV infection the incidence of all forms of tuberculosis is further aggravated all over the world. Both sexes are equally effected.

The spinal disease is always secondary to a primary lesion and occurs due to hematogenous spread. The primary focus may be active or quiescent and may be in the lungs, mediastinal lymph nodes, kidneys and other viscera. On an average, an involvement of 3 - 4 vertebrae at the time of presentation has been reported. As elsewhere, the spinal tuberculosis is a granulomatous disease. Marked exudative reaction is a common feature of spinal tuberculosis. A cold abscess mostly comprised of serum , leucocytes, caseous material, bone debris and bacilli, penetrates the ligaments and migrates along the facial planes often presenting far from the site of infection.

Clinically there are four types :

1. Para discal lesion begins in the metaphysis, erodes the cartilage and destroys the disc, resulting in narrowing of the disc space.

2. Central type begins in the midsection of the body which gets softened and yields under gravity and muscle action, leading to compression, collapse and bony deformation.

3. Anterior lesions lead to cortical bone destruction beneath the anterior longitudinal ligament. Spread of the infection is in the subperiosteal and sub ligamentous planes resulting in the loss of periosteal blood supply to the body with resultant collapse. Other factors such as periarteritis and endarteritis contribute to the collapses.

4. In appendicle type, the infection settles in the pedicles, the laminae, the articular processes or the spinous processes and causes initial ballooning of the structure followed by destruction.

Tuberculous spondylitis commonly occurs in the thoracic, followed by lumbar and cervical spines which more often occurs in the pediatrics group.

Clinical features:

1. Back pain is a predominate (70%) feature with stiff spine and Para vertebral muscle spasm. A soft tissue swelling or mass is often obvious. There is 20% incidence of cold abscess and about 90% incidence of angulations of the spine in the form of kyphosis or gibbus.

2. Systemic symptoms may or may not be there.

3. The most serious is the neurological involvement with overall incidence of about 30% and the deficit depends on the site, the direction of spread and pathological changes produced. The risk is highest in the region of cervico-thoracic region.

The cord may be involved in any phase, the active phase within the first 2 years or in later years after the disease has become quiescent. The cause in most cases is compression, which may be an abscess, granulation tissue, sequestrated bone and disc or pathological subluxation in active disease.

In healed diseases the deficit may be due to transverse ridge of bone anterior to the cord, due to angulations of the spine or healing, stretching or attrition of the cord due to spinal deformity and or fibrosis of the dura.

In a given case more than one factor may contribute to the pathogenesis. Non compressive causes such as endarteritis, periarteritis or thrombosis of the arterial supply of the cord.

As mentioned earlier, cervical spine involvement is rare (1%) more often seen in children. It is characterized by a more diffuse involvement of the lower cervical spines the formation of retropharyhngeal abscesses, often causing respiratory distress. The adult form is usually confined to a single body and more commonly results in kyphosis and cord compression.

TB of CV may cause atlanto axial subluxation, upward translocation of the dens, cervico medullary compression of tuberculous abscess or direct invasion by the disease. The disease infiltrates the ligaments which give way. Incidence of associated lesions vary between 40 - 50%.Simultaneous involvement of other bones has been reported to be between 12-15%.

Diagnosis:

Suspicion is the first step in diagnosis. No diagnostic procedure either singly or in combination will provide an unequivocal diagnosis.

The erythrocyte sedimentation rate is often raised. The mantoux test is generally positive.

A negative mantoux does not rule out a tuberculoma. ELISA (enzyme linked immunoabsorbent assay) tests of the serum and CSF may be help.

General investigations should include a search for a primary.

CT and MRI have helped in early diagnosis and follow-up with medical management. Multiple lesions are often seen.

Imaging:

A. Plain X-ray :

Lytic areas less than 1.5 cm in diameter are not demonstrated. At least 30-40% of calcium should be lost before it shows up as a radio lucent area on a plain X-Ray. Narrowing of the disc space is the earliest finding, and when associated with a loss of definition of the paradiscal margin, the diagnosis is obvious in paradiscal type which is the commonest type. In central type, the loss of normal trabeculae may show areas of destruction. Occasionally body may be ballooned out as a result of the accumulation of inflammatory debris which expands the weakened cortical bone in the anterior type, the infection begins beneath the anterior longitudinal ligament. The front and the sides of the body show erosion. In appendicular type erosion of the region involved.

In late cases of all types there is frank erosion and collapse with areas of sclerosis because and concomitant bone regeneration and fusion of the vertebral bodies. A tense Para vertebral abscess may cause scalloping of the vertebral bodies.

In addition to the focal osseous changes, plain X-Ray may show kyphosis deformity and lateral curvature when large number of adjacent vertebrae are involved. Soft tissue shadows may suggest Para vertebral abscess or extension of tuberculous granulation tissue.

CT scan:

It shows body lysis and destruction at an earlier stage more accurately. Additionally it can depict paraspinal abscess and granulation tissue distinctly. Enhancement with contrast may aid in better delineation. CT is also useful during aspiration of suspected areas of infection.


Koch's-CV junction	Koch's -archnoidits	Koch's cervical spine with cold abscess

Koch's dorsal spine	Koch's dorsal spine with cold abscess	Koch's neural arch (laminae involvement)

MRI : With its high resolution, direct multiplanar imaging, detection of early lesions and also associated lesions such as abscesses, skip lesions and epi and intradural involvement, MRI is the obvious choice of investigation. Contrast MRI aids in better delineation and also in differentiating the lesion from the surrounding edema. T1 images show decreased signal from the lesion within the 30 days and narrowing of the disc space and also loss of signal from the nuclear pulpous. T2 may show increased signal from the involved body and the disc narrowing with normal decreased or increased signal higher than normally seen. Response to
therapy may be seen as an increase in the signal intensity of T1 compared to previous images.	Epidural abcess-MRI T1
Treatment: Medical: Conservative therapy is advised by many. Bed rest and antitubercular therapy alone have been found sufficient in most cases including early cases of paraparesis. Bed rest is advised for 4-6 weeks till the pain and spasm disappear and general health improves. They are then allowed to get up, but wear braces which can be discarded after 6-8 weeks.
The chemotherapy is continued for 18 months.	Epidural abcess- MRI T2

Chemotherapy is similar to intracranial tuberculosis:

Drug: Dosage: Side effects:

Rifampicin: 10mgms/kg Liver toxicity

Isoniazid: 10mgms/kg peripheral neuritis

Pyrizanamide: 20mgms/kg Liver toxicity.

Ethambutol: 15mgms/kg. Optic neuritis.

Surgery:

A diagnostic Ct guided needle biopsy is routine in well established centers. Other indications are:

1. Neurological deficit which is not improving or worsening with in 4 weeks of adequate chemotherapy - Too long a delay may lead to problems like extradural fibrosis which may be difficult to eradicate.

2. Development of progressive neurological signs while on adequate therapy.

3. Rapid onset paraplegia and in patients in an advanced stage of disease when delay is risky.

4. Posterior spinal disease (because it is rare).

5. Late onset paraparesis - usually the results are less satisfactory in healed cases. Patients with active disease respond better.

6. Correction of kyphosis which has not responded satisfactorily to braces and proper posturing.

Surgery may involve

1. Simple drainage of the cold abscess which would be sufficient in these cases when the tension inside the abscess is the cause of cord compression.

2. A direct approach thro an anterior or lateral route and radical removal of the compressing elements such as debris, sequestrae or granulation tissue with or without bone grafting. Medical Research Council working party on tuberculosis of spine study showed that fusion occurred earlier and in a higher proportion in the group with bone graft but at 5 and 10 years there was little difference between the two. At 10 years there was a small reduction in the angle of kyphosis in the bone grafted group and a small increase in the angle in the non grafted series.

3. In some centers in developed countries and in modern Neuro/Orthopedic practice, instrumentation has a significant place with good results and early mobilization. The main problem is the formation of a focus of infection and of course the cost involved. The current trend is to use instruementation.

4. Laminectomy is an unsatisfactory procedure except in a few cases when the compressing element is posterior, a condition seen in tuberculous disease of the neural arch.

5. In the case of cranio vertebral tuberculosis, urgent skull traction to reduce the atlanto axial subluxation is mandatory. In some such closed reduction may not be satisfactory. They require excision of the diseased bone granulation tissue thro a transoral route followed by a C1 - C2 posterior Fusion either at the same sitting or at a second stage.

B) Extradural involvement:

Majority are secondary to vertebral lesion. Occasionally we come across a lesion without any bony lesion. It is likely they are secondary to a small hidden focus in the adjoining vertebra. The diagnosis is often made post operatively, as there is nothing specific in X-Ray or in MRI. The granuloma usually encircles the dura.

Laminectomy and excision followed by a complete course of ATT is the usual practice.

C) Intradural intramedullary involvement :

Much less frequent . With absence of any indication of tuberculosis elsewhere the diagnosis is made with histopathology.

D) Intradural extramedullary involvement:

It is the least common and the diagnosis made with histopathology. Only eleven cases have been reported.

E) Tuberculous archnoiditis:

It is seen in patients who have had tuberculous meningitis. Treatment is unsatisfactory. Microsurgical techniques may provide some relief. If it is localized, intrathecal administration of hydrocortisone or hyaluronidase have been claimed to be effective.

PROGNOSIS:

Early diagnosis with better imagings and the 2nd line of drugs has greatly improved the prognosis without necessitating surgery. Recurrence may be seen if the drug therapy is irregular or discontinued after a short time, which may be the cause for the emergence of drug resistant cases, which are on the increase lately. A number of these cases ultimately respond to continued therapy and to carefully worked out combinations with or without second line of drugs.