Tuberculosis of the spine is one of the oldest diseases afflicting humans. Evidences of spinal tuberculosis have been found in Egyptian mummies dating back to 3400 BC
1. The descriptions in Rigveda, Atharvaveda and Charak Samhita are the oldest known texts in the world literature relating to this disease
2. The association of paraplegia and kyphotic deformity of the spine was first noticed by Sir Percival Pott
3. Tuberculosis was a leading cause of mortality in the beginning of the twentieth century
4. Improvement in the socio-economic status led to a major decline in the prevalence even before the introduction of antituberculous drugs. However, it continues to be a major public health problem in developing countries. Malnutrition, poor sanitation, and exanthematous fever are the factors contributing to the spread of the disease. In the United States, there has been a steady increase in the prevalence of pulmonary as well as extrapulmonary tuberculosis
5. This is largely due to impairment of immune system by the human immunodeficiency virus leading to reactivation of latent infection and a likelihood of progression to active disease
6. The commonest causative organism for spinal tuberculosis is Mycobacterium tuberculosis, an acid-fast bacillus growing only on media enriched with egg and potato base or serum. The practice of boiling of milk before consumption has limited the Myco bovis-caused disease and the Myco africanum is geographically limited to Northwest Africa
7. Topographically, spinal tuberculosis constitutes about half the cases of skeletal tuberculosis
8. The dorsal spine is involved in half the cases of spinal tuberculosis. The disease is always secondary to a primary visceral focus which may be in the lungs, lymph nodes or kidneys. Extrapulmonary tuberculosis is more common in children than in adults, the commonest site being the superficial lymph nodes
9. A minimum time lag of 2 to 3 years is present between the development of primary focus and manifestation of the disease in the spine. The bacteria may reach the spine through the arterial circulation or the Batsons plexus of veins. Initially, two contiguous vertebral bodies are involved due to a common vascular supply. Destruction of vertebral bodies compromises the nutrition of the intervertebral disc and leads to progressive disc destruction10 and vertebral collapse.
Demography of Spinal Tuberculosis
In the Indian population, spinal tuberculosis is predominantly a disease of the young, the usual age of presentation being the first three decades of life. Reports from developed countries indicate a much older patient population, the median age at diagnosis being sixty-one years11. In most series, the disease has been found to affect males and females in equal proportions12,13.
Diagnosis of Spinal Tuberculosis
Clinical presentation The clinical features of tuberculosis of the spine include insidious onset of localised pain in the spine. This is usually accompanied by fever, malaise, anorexia and weight loss. Clumsiness in walking and weakness in lower limbs may be present. There may be evidences of associated extraskeletal tuberculosis like cough, expectoration, lymphadenopathy, diarrhoea and abdominal distension. Presence of hoarseness, dysphagia, respiratory stridor or torticollis indicate cervical involvement.
Physical examination of the spine reveals localised tenderness and paravertebral muscle spasm. A kyphotic deformity due to prominence of spinous process may be evident due to collapse and anterior wedging of vertebral bodies. Tuberculous necrotic material from the cervical spine may collect in the form of a cold abscess in the retropharyngeal region; at the posterior border of sternomastoid; in the back of neck along spinal nerves and in the axilla along axillary sheath. Involvement of the dorsolumbar spine may lead to cold abscess in the rectus sheath and lower abdominal wall along the intercostal, ilioinguinal and iliohypogastric nerves; in the thigh along the psoas sheath; in the back along the posterior spinal nerves; in the buttock along superior gluteal nerve; in the Petits triangle along the flat muscles of abdominal wall or, in the ischiorectal fossa along the internal pudendal nerve. The presence of a sinus in the back with a thin watery discharge is a strong evidence of tuberculous involvement of the posterior arch of vertebral bodies. Rarely, tuberculous spondylitis may present as synovitis of posterior vertebral articulations, atlanto-occipital or atlanto-axial joints or as spinal tumour syndrome.
Radiographs Radiographs are the first line of investigations to substantiate or refute a clinical diagnosis of tuberculosis of the spine. The commonest radiological presentation is the paradiscal lesion. The earliest signs are narrowing of the joint space and loss of definition of the paradiscal margin of vertebral bodies. The narrowing may be due to atrophy of the disc or herniation of nucleus pulposus into the vertebral bodies. The collection of tuberculous granulation tissue and necrotic material leads to formation of paravertebral abscess. It is evident on plain radiographs as a fusiform or globular radiodense shadow or a bulging of the lateral border of psoas shadow. Long standing abscesses may erode the anterior margins of the vertebral bodies producing a scalloped appearance. Wedging of vertebral bodies leads to a kyphotic deformity.
Rare radiological presentations of tuberculosis of the spine include central type, anterior type and appendiceal type. Central disease presents as areas of destruction, ballooning of vertebral bodies and later as concentric collapse. Anterior type is more common in the paediatric dorsal spine and appears as erosion of anterior margin of vertebral bodies. Appendiceal disease is involvement of the posterior arches. Isolated posterior arch disease is difficult to diagnose with conventional radiography but may be suspected by the presence of erosive lesions and paraspinal shadows. CT scan examination and MR scanning are increasingly being used to diagnose posterior arch disease. Presence of lateral shift indicates panvertebral disease14.
Haematological investigations The erythrocyte sedimentation rate is usually elevated but is neither specific nor reliable in the diagnosis of spinal tuberculosis. The enzyme-linked immunosorbent assay (ELISA) has a reported sensitivity of 60 to 80 per cent15. Stroebel et al16 have reported a sensitivity of 94 per cent and a specificity of 100 per cent for osteoarticular tuberculosis by ELISA using antibody to mycobacterial antigen6. The polymerase chain reaction is being tested for the diagnosis but is currently not available in all clinical settings15. A brucella complement fixation test may be useful in endemic areas as brucella can clinically mimic tuberculosis.
CT/MR scanning The wide availability of CT scanning and MR scanning has increased the use of these modalities in the management of tuberculosis of the spine. CT scanning can determine posterior extension and encroachment of inflammatory tissue, bone or disc material17, and diagnose posterior spinal disease and involvement of sacroiliac joints and sacrum. It helps in guiding biopsies and planning operative interventions. MR scanning is done to detect soft tissue masses, appendicular tuberculosis, extent of disease and the subligamentous spread of tuberculous debris. This spread under the anterior and posterior ligaments is strongly suggestive of tuberculosis of the spine but is not pathognomonic18. MR is also useful in evaluation of intramedullary lesions and extradural spread and to differentiate between cord compression by granulation from that by bone and disc.
Skin tests A positive Mantoux test can be observed, one to 3 months after infection. The test may be negative in almost 20 per cent patients with active disease if the disease is disseminated, or if the patient is immunocompromised or suffering from exanthematous fevers19. Co-existent infection by human immunodeficiency virus may also give a false negative skin test20.
Bone scan Technitium (Tc) 99 m bone scan showed increased uptake in 63 per cent patients with active tuberculosis in the series reported by Weaver and Lifeso21. The remaining patients showed a cold spot due to formation of avascular segments and abscesses. The Tc-99m scan is considered to be highly sensitive but nonspecific. It may only aid to localise the site of active disease and to detect multilevel involvement.
Smear and culture Acid-fast bacilli may be demonstrated on smear examination. The Ziehl-Neelsen staining is a quick and inexpensive method but has a low positivity. Stains require a minimum of 104 bacilli per ml19 while culture shows a growth with only 103 bacilli per ml22. Moreover, cultures can be employed to determine drug susceptibility but the results are available only after a few weeks.
Biopsy The high prevalence of tuberculosis in India precludes the need of histopathological diagnosis prior to starting chemotherapy. However, a biopsy may be needed in cases of equivocal clinicoradiologic findings, lack of proper response to drug therapy and suspicion of drug-resistant strains. The method most widely used for the histopathologic diagnosis of spinal tuberculosis is computed tomography guided needle biopsy23. Alternatively, core needle biopsy may be used. The tissue obtained should be sent for culture and antibiotic sensitivity as well as histopathology.
Treatment of Spinal Tuberculosis
Medical treatment Isoniazid is the most potent antituberculous drug presently available and has a good penetration into body cavities. Rifampicin and pyrazinamide are bacteriocidal and most effective against dormant bacteria. Ethambutol is bacteriostatic and is given for a period of two to three months. The currently recommended regime for musculoskeletal tuberculosis including tuberculosis of the spine is four-drug therapy24. These include rifampicin, isoniazid, pyrazinamide and ethambutol. In children too young to be monitored for visual acuity, ethambutol is replaced by streptomycin. Ten mg of pyridoxine is given simultaneously to prevent peripheral neuropathy due to isoniazid. After three months, ethambutol is withdrawn and three-drug regime is continued for a period of further nine months. Thenceforth only rifampicin and isoniazid are continued for further six months. The total duration of therapy should be eighteen months. An alternative regime given by Tuli25 is administration of rifampicin, isoniazid and ethambutol for the first four months. In the second four months, rifampicin is replaced by pyrazinamide. In the next four months, rifampicin is given along with isoniazid and the last four months are covered by only isoniazid. This adds up to sixteen months of drug therapy.
The Medical Research Council of the United Kingdom has shown drug therapy alone to be sufficient for the management of spinal tuberculosis26. The likelihood of progression of kyphosis is more in the dorsal spine while children may have a correction of the deformity due to continued growth of the end plates27.
The middle path regime given by Tuli25 is the most widely accepted protocol for the management of patients of spinal tuberculosis. This regime recommends non-operative treatment for most of the patients by antituberculous chemotherapy, bed rest and spinal braces. The patients are monitored clinically, radiologically and haematologically every three months. Abscesses are aspirated and streptomycin and isoniazid are instilled. The onset of recovery after chemotherapy may be delayed up to three months. Sinuses and abscesses usually subside after two to three months of regular chemotherapy. Evacuation of abscess may be needed if the size of abscess increases despite medical treatment. Surgery is recommended only where indicated.
Surgical treatment The indications for operative intervention in spinal tuberculosis are marked neurologic deficit, lack of response or worsening neurologic deficit despite drug therapy, severe or progressive kyphosis, retropulsed bone fragments in the canal, large abscess causing respiratory embarrassment and spinal instability28.
The Medical Research Council study in Hong Kong has shown better results by radical debridement and arthrodesis as compared to radical debridement alone29. Both the procedures had similar results regarding relief of pain and neurologic recovery. However, the addition of arthrodesis gives better correction of kyphotic deformity and reduces risk of progression.rior structures. This allows adequate debridement of diseased tissue and decompression of the spinal cord, also tissue can be obtained for histopathology and culture. Posterior approach is indicated in cases of appendiceal involvement and where posterior stabilisation is needed prior to anterior decompression. Posterior stabilisation with metallic implants does not increase the risk of infection and allows earlier mobilisation30.
Anterolateral decompression through the costotransversectomy approach comprises removal of two to four ribs, the transverse process, pedicle and part of the body of the vertebra. The sequestered body, disc and tuberculous debris are removed and the paraspinal abscess is evacuated. The cord is exposed anteriorly over a length of 3 to 6 cm to relieve external pressure over the cord. Bone grafting may or may not be done with this procedure. The patient is advised absolute bed rest for theree months and then gradually mobilised in a spinal brace. The brace is retained for 12 to 18 months.
Hodgson and Stock31 recommended removal of all diseased tissue, pus, sequestra, aseptic necrotic bone and devitalised discs as far back as the spinal cord and bridging by autologous bone graft. They employed a left transpleural approach and excised the entire vertebral body and replaced it by the rib graft. Postoperative ambulation was allowed after a minimum of three months of bed rest.
Late-onset paraplegia may be due to sharp osseous kyphosis, vertebral canal stenosis, fibrosis around neural elements or tuberculous sequestra. The surgical treatment is difficult and recovery is usually delayed and incomplete. Myelopathic changes in the cord contribute to the poor prognosis32. Operative decompression should be done when there is no response to three to four weeks of treatment by four-drug regime. In the cases presenting late, operative intervention done as late as nine months has shown a beneficial effect. Neurological deficit of more than one year duration rarely improves after surgery32.
Tuberculosis of the spine is a preventable and treatable cause of spastic paraplegia. Early diagnosis and comprehensive treatment are needed to control this pubic health problem.
Note: Sanjeev Agarwal, MS, DNB, MNAMS, Senior Resident Department of Orthopaedics, King Georges Medical College, Lucknow 226003