Spinal tuberculosis or Pott's disease is an infection of the vertebral column caused by Mycobacterium tuberculosis. This condition is of great diagnostic importance due to its link to neurologic deficits and painful spinal deformities.
Spinal tuberculosis (TB) can cause compression of peripheral nerves leading to loss of sensation and motor functions. There are two types of this affliction:
Lesions of tuberculosis affecting the vertebrae are characterized with spreading to adjacent spinal structures, provocating osteomyelitis, and arthritis in numerous vertebrae [1]. TB can cause the destruction of the bone tissue that leads to the development of kyphotic or kyphoscoliotic disfigurement and possible compression of root nerves with the collapse of the vertebrae [2]. Spinal canal can narrow due to the protrusion of granulations, lesions like cold abscesses developed in the course of the TB infection or direct infiltration. Cold abscesses are known to spread in subligamentous fashion, considering the bacteria cannot exert a lytic effect in these tissues [1] [2].
Patients with spinal TB present with local symptoms such as pain in the affected area, reduced amplitude of movement due to compression, and loss of function. Non-specific complaints are fever, night sweats, signs of wasting like reduction of weight, loss of appetite, and fatigue [3] [4] [5].
Neurological assessment can be made using the American Spinal Injury Association (ASIA) impairment scale which classifies neurologic deficit into grades. Although alternative methods are available, ASIA classification is used more frequently due to the correlation with findings from the magnetic resonance imaging scans [2].
Spasticity, progressive loss of sensory and either partial or complete motor function is expected if the tuberculosis lesions are not treated [6].
It is important to differentiate spinal TB from other causative agents that can establish lesions in the spine like fungal or pyogenic infections. Metastatic or primary tumors are also subjected to differentiation [1].
A positive skin test is an indicator of M. tuberculosis involvement, despite that, additional studies have to be performed to confirm the disease. This is particularly important in endemic regions where TB is widespread [7].
Biopsy and subsequent procedures associated with polymerase chain reaction amplification methods give rise to an accurate and fast diagnosis of the infection and the causative agent. This is due to difficulties obtaining M. tuberculosis cultures that can take a long time to cultivate and the results may be unreliable, even false negative [1].
Imaging studies are performed to determine the exact location of the tuberculosis lesions and estimate the grade of infiltration. Computed tomography (CT) scan or plain radiography are effective in visualizing the pathologies in the bone structures like the collapse of a vertebral body or bone tissue destruction. Narrowing or even absence of intervertebral space is noted as well [3]. Conversely, a phenomenon of ivory vertebra is possible. It is described as increased opacification of the vertebral body with no changes in size or contours. This renders the image to appear heterogeneous [2].
Magnetic resonance imaging (MRI) is a more accurate radiologic study that can exhibit characteristics of soft tissues and presence of abscesses [7]. Sagittal and axial planes are used. Spinal cord edema and signs of compression in addition to end-plate disruption may be seen [2]. Atypical findings of the spinal TB include lesions not associated with vertebral discs or only small-scale disc involvement, as well as no evidence of soft tissue abscesses [8].