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.
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
- Arachnoidal membrance[no dural involvement]
- Intramedullary involvement
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 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.
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