Tuberculosis Of The Spine

Introduction

Tuberculosis of the spine also known as Koch's spine and Tuberculous Vertebral Osteomyelitis is the commonest form of skeletal tuberculosis and accounts for 88% of chronic vertebral infections. 30% of Kochs' spine occurs before the age of 10 years.

Incidence of Koch's Spine

There are 30 million cases of tuberculosis in the world. 6 million cases of sputum positive tuberculosis are in India. 1-3% of cases have skeletal tuberculosis.

Tuberculosis of the Spine - Pathophysiology

Vertebral affection occurs due to hematogenous dissemination from a primary infected organ (usually pulmonary or lymph node). The primary focus may be active or quiescent, apparent or latent.

The simultaneous involvement of paradisical parts of two contiguous vertebrae is the typical lesion. This is due to the common blood supply of adjacent vertebrae. The other type of affections is the central type, anterior, and posterior type.

Histopathological picture of spinal TB

Pathologically, tuberculosis occurs in two forms:

• The granulomatous inflammation characterized by granulation tissue and tubercles.

• Caseous type associated with abscess and sinus formation.

Following infection, there is marked hyperemia and osteoporosis. Osseous destruction takes place by lysis of bone, which is thus softened and easily yields under effects of gravity and muscle action, leading to compression, collapse, and deformation of bone. Necrosis also takes place due to ischemic infarction of segments of bone. This change is secondary to arterial occlusion due to thrombo-embolic phenomenon, endarteritis, and periarteritis.

The intervertebral disc is not involved primarily because of its avascularity. Damage to the vertebral endplates and adjacent articular cartilage results in the loss of its nutrition. The disc gets degenerated and may become separated as a sequestrum.

Presentation

The majority of the patients present late with a long duration of symptoms. The presenting feature may be a deformity or neurological deficit.

Pain or deformity may be the presenting complaint. Pain is insidious in onset, continuous, and associated with spasm of paraspinal muscles. The deformity is in the form of a localized kyphosis, which is tender on percussion. The patient may have a cold abscess, which can present itself far away from the vertebral column along fascial planes or along the course of neurovascular bundles. The common sites are:

• Along the paraspinal region in the neck-posterior triangle of the neck, anterior triangle, and as a retropharyngeal abscess.

• In the dorsal spine in the posterior mediastinum or along the course of intercostal nerve, as an abscess in the midaxillary line or parasternal.

• In the lumbar region as a psoas abscess or an abscess in the Petit's triangle. The abscess may track along nerves sometimes up to the knee.

Constitutional symptoms in the form of fever, malaise, loss of weight, loss of appetite may be present.

Neurological complications occur in 10 - 30% of cases. They are of two types:
Early Onset: This occurs within 2 years of the disease. Inflammation, edema, abscess, caseous tissue, or sequestrum from vertebral bodies producing neural compression. The prognosis of early-onset paresis is good following appropriate management.

Late-onset paresis: which occurs after 2 years of onset of disease and result from stretching of the cord over an internal gibbus causing myelomalacia and gliosis of the cord, or may result from mechanical pressure on the cord or recrudescence of disease. The prognosis is poor, as permanent degenerative changes may have occurred in the cord.

Investigations

Radiological:

• X rays of the spine: show a reduced disc space and loss of definition of the paradisical margins. The presence of paravertebral, prevertebral shadow indicates that an abscess is present. The central body affections appear as a flattening of vertebrae. The anterior type appears as wedged vertebrae.

• MRI or CT scan is used to define the cause of neurological deficit and status of the cord.

Blood investigations:

Other investigations:

As skeletal tuberculosis is paucibacillary, cultures are usually negative. The confirmation of the diagnosis is on histopathology.

Tuberculosis of the Spine - Differential Diagnosis

The differential diagnosis includes congenital deformities of the spine, pyogenic or fungal infections, Scheuermann's disease.

Treatment

Anti-tuberculous chemotherapy and bed rest and later protective bracing and mobilization form the mainstay of treatment. Bactericidal drugs are preferred and short course chemotherapy is under trial. Operative intervention is required when:

• There is a progressive neurological deficit

• No response to conservative management

• Persistent neurological deficit

• Decompression of large abscesses

The involvement of more number of contiguous vertebrae and a more severe deformity may be anticipated.

The various surgeries are:
Draining of an abscess.

Decompression and scraping of the infected lesion.

Decompression with bone grafting.

In presence of a deformity correction of the deformity and stabilization by internal fixation and fusion.