Tuberculosis of the spine is a serious infection caused by the bacterium Mycobacterium tuberculosis. This condition is a form of extrapulmonary tuberculosis, meaning the infection has spread outside the lungs, and is historically known as Pott’s disease. While less common than pulmonary tuberculosis, it is one of the most destructive types of bone tuberculosis. The infection targets the bones of the spinal column, leading to structural damage and potential long-term disability if not treated promptly.
The Mechanism of Spinal Damage
The infection typically begins when Mycobacterium tuberculosis travels through the bloodstream, usually from the lungs, in a process known as hematogenous spread. The bacteria lodge in the highly vascularized anterior part of the vertebral body. This initial seeding marks the start of the destructive process, usually involving the lower thoracic and upper lumbar regions of the spine.
From the vertebral body, the infection spreads to the adjacent intervertebral disc, leading to its destruction and the involvement of the next vertebra. The infection causes chronic inflammation resulting in caseous necrosis, where the bone tissue dies and liquefies. This progressive destruction weakens the spinal column, causing the vertebral bodies to collapse.
The collapse and destruction can lead to the formation of a “cold abscess,” a collection of pus and debris that lacks the typical signs of acute inflammation. These abscesses can track along muscle planes, such as the psoas muscle, further compromising spinal integrity. The loss of bony support and the presence of abscesses ultimately destabilize the spinal column.
Recognizing the Symptoms
The earliest and most frequent symptom is localized back pain, ranging from a dull ache to severe discomfort. This pain is often exacerbated by movement and may become worse at night. Stiffness in the back and muscle spasm near the affected area are also common.
Patients may also exhibit constitutional symptoms, which are general signs of active systemic infection. These include unexplained weight loss, loss of appetite, low-grade fever, and drenching night sweats. These non-specific symptoms can complicate early diagnosis, as they mimic several other conditions.
As the vertebral bodies collapse, the spinal column can develop a characteristic deformity called kyphosis, commonly known as a hunchback. When this deformity is angular and sharp, it is referred to as a gibbus deformity. The most serious symptoms arise if the collapsing bone or cold abscess compresses the spinal cord or nerve roots, leading to neurological deficits. These manifest as weakness, numbness, tingling, or in severe cases, paralysis (Pott’s paraplegia).
Diagnostic Procedures
Confirming a diagnosis requires a combination of clinical assessment, advanced imaging, and definitive laboratory confirmation. Imaging studies visualize the extent of bone destruction and soft tissue involvement. Plain X-rays may initially show a loss of intervertebral disc height and bony destruction, particularly in advanced cases.
Magnetic Resonance Imaging (MRI) is the most sensitive imaging method for early evaluation. MRI provides detailed views of soft tissues, clearly showing cold abscesses, spinal cord compression, and damage to the vertebral bodies and discs. Computed Tomography (CT) scans are also useful, offering superior detail on bony destruction and calcification within the abscesses.
A definitive diagnosis relies on identifying the Mycobacterium tuberculosis bacteria itself. This is often achieved through a CT-guided needle biopsy, which obtains a tissue sample from the affected bone or abscess. The sample is then tested using methods like Acid-Fast Bacilli (AFB) staining, culture, or molecular tests such as Polymerase Chain Reaction (PCR). Immunological blood tests, such as the Tuberculin Skin Test (TST) or Interferon Gamma Release Assays (IGRA), can indicate exposure to the bacteria but do not confirm active spinal disease.
Treatment Protocols
The cornerstone of managing spinal tuberculosis is a prolonged course of multi-drug antituberculosis therapy (ATT). This medical treatment aims to eliminate the infection and is effective in most uncomplicated cases. The standard regimen involves four first-line drugs—isoniazid, rifampicin, pyrazinamide, and ethambutol—administered together for an initial intensive phase of two months.
This is followed by a continuation phase, usually consisting of only isoniazid and rifampicin, for several more months. The total duration of treatment is commonly recommended to be between 6 and 12 months, depending on disease severity. Consistent adherence to this drug regimen is crucial to prevent complications and the development of drug-resistant strains.
Surgical intervention is considered for specific indications and is not necessary for every patient. Surgery is reserved for cases involving significant spinal instability, a large, non-resolving abscess, or failure of medical therapy. The most urgent indication is a progressive neurological deficit, such as weakness or paralysis, caused by spinal cord compression. The goals of surgery include debridement, decompressing the spinal cord, and stabilizing the spine through fusion to prevent further deformity.