Atypical Spinal Tuberculosis

Atypical spinal tuberculosis refers to the presentation of tuberculous disease of spine in a manner that is not usual presentation.

The usual presentations of spinal tuberculosis have been discussed in great detail in the following article.

Tuberculosis of Spine- Presentation, and Treatment

Atypical spinal tuberculosis may involve other parts of the vertebra or it may affect the neural and perineural tissue.

Atypical spinal tuberculosis is relatively uncommon and therefore, more difficult to diagnose.

Atypical spinal tuberculosis can be of the following types

• Tuberculosis of Posterior Complex
• Intraspinal Tuberculous Granuloma (Tuberculoma)
• Extradural Granuloma
• Subdural Granuloma
• Single Vertebra Disease

These entities are discussed below.

Posterior Complex Tuberculosis

This type of atypical spinal tuberculosis occurs in the posterior elements of the vertebral arch.

It has been reported in pa­tients suffering from HIV infection.

The lesion commonly arises in the dor­sal, dorsolumbar, and lumbar vertebrae. Cervical lesions involving the posterior complex are extremely rare.

The lesion may be present in isolation or in com­bination with each other involving the following sites-

• Vertebral arch –  lamina and pedicles
• Processes of the vertebral arch i.e. the transverse ar­ticular and spinous process.
• A combination of both

It must be emphasized that typical spinal tuberculosis is mainly an anterior disease.

In this type of atypical spinal tuberculosis that involves posterior complex, the patient may present as back pain and the vertebral region may be tender. But radiographic changes will not be visible as in typical disease.

Sometimes, a posterior abscess may be noted which is a unique feature of the posterior disease.

So in presence of a normal x-ray, a  CT scan or an MRI is done early to avoid delay in diagnosis. Ct and MRI are able to pick the disease at an earlier date.

CT Scan or MRI may be able to determine

• Site and extent of the lesion
• Presence of any vertebral body involvement
• Encroachment of the spinal canal. These are able to pick up the diagnosis at an earlier stage.

The lesion may occur in elements of the vertebral arch including the laminae, pedicles, transverse or spinous processes. Rarely the apophyseal joints may be in­volved.

The primary mode of treatment is anti-tuberculosis chemotherapy. Neurological involvement may warrant surgical treatment.

Intraspinal Tuberculous Granuloma (Tuberculoma)

Tuberculosis can involve neural and perineural tissue directly invading the spi­nal cord or meninges. This type of atypical spinal tuberculosis may involve

• Extradural space
• Subdural space
• Both
• Arachnoidal membrance[no dural involvement]
• Intramedullary involvement

Extradural Granuloma

Because of the neural involvement, neural weakness is the usually earliest symptom apart from vague back pain. The neural symptoms are caused by the compression of the cord.

Because the lesions do not involve the bones, the x-rays are normal.

MRI or CT myelography is required to lo­calize these lesions.

An extradural granuloma may engulf the cord and only drug treatment may lead to scarring and permanent neurological loss.

The granulomas may occur in association with bony involvement too. In such cases, anterior or anterolateral decompression is recommended as indicated for the typical disease.

If there are associated neural arch lesions or when no os­seous lesion is present, laminectomy and ex­cision of the extradural granuloma are recom­mended.

Subdural Granuloma

Subdural granulomas present with compressive myelopathy but with normal x-rays.

JMyelography, myelo CT or MRI is re­quired to localize the lesion.

Laminectomy at the level of the lesion is recommended.

Intramedullary Tuberculoma

These are very rare. The patient presents with a picture of severe spinal cord compres­sion with a rapidly progressive course.

MRI is the most useful in­vestigation sequential.

Anti-tubercular chemotherapy is the mainstay of the disease.

Single Vertebral Disease

The typical tubercular disease of the spine involves the bodies of two contiguous vertebrae.

Single vertebral disease without involve­ment of the disc spaces is also considered atypical spinal tuberculosis.

It may lead to the appearance of a lytic lesion of the vertebra or may cause a collapse of the vertebra leading to vertebra plana [also seen in eosinophilic granuloma].

The vertebra collapses because the diseased vertebral body is weakened by the permeation of granulation tissue and collapses. It protrudes radially and may cause a neurological deficit.

A plain x-ray will show the collapse of a single vertebral body with preservation of ad­joining disk spaces.

CT scan and MRI may help in differenti­ating this atypical spinal tuberculosis from other lesions such as eosinophilic granuloma, solitary plasmacytoma, metastatic disease.

However, the histological evidence is re­quired in these atypical lesions and all efforts should be made to establish a tissue diag­nosis.

Neurological deficit if present warrants ante­rior decompression. Laminectomy is contraindicated as it may worsen the neurological deficit.

Other forms of Atypical Spinal Tuberculosis

• Multiple vertebral skip lesions
• Giant tuberculous abscess with little or no demonstrable bony focus.
  • May present as a cold abscess in the thigh, loins or as a psoas abscess.
• Sclerotic Vertebrae with intervertebral bony bridging.
  • Seen occasionally in healthy individu­als with good immunity.
• Pan Vertebral Disease
  • Concomi­tant involvement of anterior and posterior elements.
  • Have severe instability