Spinal tuberculosis (TB) is a serious infection of the spine caused by the bacterium Mycobacterium tuberculosis, which is the same organism responsible for pulmonary TB. This condition is a form of extrapulmonary tuberculosis, meaning it occurs outside of the lungs, and it is known historically as Pott’s Disease. Spinal TB represents the most destructive form of skeletal tuberculosis, capable of causing significant damage to the vertebral column. Recognizing and managing this infection promptly is essential, as delayed treatment can lead to severe and permanent spinal deformity and neurological impairment.
The Mechanism of Spinal Infection
The infection typically begins elsewhere in the body, most commonly in the lungs, before spreading to the spine. This dissemination occurs primarily through hematogenous spread, where the bacteria travel through the bloodstream from the primary infection site. Vertebral bodies are particularly susceptible to this process due to their rich vascular supply, which includes end arteries where blood flow is relatively sluggish. This environment allows the Mycobacterium tuberculosis bacilli to localize and colonize the bone tissue.
Once the bacteria settle, the infection usually begins in the metaphyseal region of the vertebral body and then spreads. It tends to affect the thoracic and lumbar regions of the spine most frequently, with the lower thoracic vertebrae being the most common site of involvement. The bacteria trigger a destructive inflammatory response that leads to the formation of characteristic tuberculous granulomas and caseous necrosis (a soft, cheese-like material).
This necrotic process gradually destroys the vertebral body and often spreads to the adjacent intervertebral disc space, causing disc narrowing and further destabilization. The structural destruction of the vertebrae, coupled with the formation of large collections of pus known as cold abscesses, ultimately causes the spinal column to collapse.
Recognizing the Signs and Symptoms
The clinical presentation of spinal TB is often insidious, leading to delayed diagnosis. Systemic symptoms, which are common to all forms of active tuberculosis, include a low-grade fever, drenching night sweats, and unexplained weight loss. Patients may also report general malaise and a loss of appetite. These non-specific signs can precede localized symptoms by weeks or months.
The most prominent localized symptom is chronic, deep-seated back pain. This pain is typically localized to the area of infection and tends to worsen over time, frequently becoming more intense at night or with movement. Spinal stiffness and localized tenderness over the affected vertebrae are also common findings. The destructive nature of the infection leads to the collapse of the vertebral bodies, which can result in noticeable spinal deformities.
The most recognized deformity is kyphosis, an abnormal forward curvature of the spine that creates a hunchback appearance. A severe, sharply angled kyphosis is specifically known as a gibbus deformity. The localized infection can also track into adjacent soft tissues, forming a paravertebral or psoas abscess, which may present as a painful lump in the groin or flank region.
Neurological complications arise when the spinal cord or nerve roots are compressed by the abscess, granulation tissue, or bony fragments from the collapsing vertebrae. Signs of potential spinal cord involvement include weakness in the arms or legs, numbness, or a tingling sensation in the limbs. In severe cases, significant compression can lead to difficulty walking, loss of motor function (paralysis), and a loss of bladder or bowel control. Neurological deficits are present in a significant minority of patients.
Diagnostic Confirmation and Assessment
Diagnosing spinal tuberculosis requires a combination of clinical suspicion, laboratory studies, and detailed imaging to assess the extent of the disease. Imaging studies are essential for visualizing the characteristic bone destruction and soft tissue involvement caused by the infection. Plain X-rays may initially show subtle signs but are better at revealing late-stage changes, such as vertebral collapse and disc space narrowing.
Computed Tomography (CT) scans offer superior detail of the bony destruction, identifying features like vertebral endplate rarefaction and the presence of bone fragments. CT is also highly effective at demonstrating paravertebral abscesses and calcification within the soft tissues. However, Magnetic Resonance Imaging (MRI) is considered the most sensitive and accurate imaging modality for spinal TB.
MRI provides excellent visualization of soft tissues, making it the preferred method for assessing the size of cold abscesses, the extent of granulation tissue, and, most importantly, any compression or involvement of the spinal cord. The definitive confirmation of spinal TB relies on obtaining a tissue sample for microbiological and histological analysis. An image-guided biopsy, typically performed with CT or fluoroscopy, is the gold standard for collecting specimens from the affected vertebra or abscess.
The tissue collected is then subjected to culture to grow M. tuberculosis, which can take several weeks, and to Polymerase Chain Reaction (PCR) testing for rapid identification of the bacterial DNA. Histological examination of the biopsy can confirm the diagnosis by revealing the presence of characteristic features like epithelioid cell granulomas and Langhans’ giant cells. This helps distinguish spinal TB from other conditions, such as pyogenic infections or spinal tumors.
Comprehensive Treatment Approaches
The management of spinal tuberculosis is primarily centered on prolonged, multi-drug anti-tuberculosis therapy (ATT). The standard first-line regimen typically involves a combination of four drugs: isoniazid, rifampicin, pyrazinamide, and ethambutol.
Treatment is divided into an intensive phase, where all four drugs are administered daily for the first two months, followed by a continuation phase. During the continuation phase, the regimen is usually simplified to isoniazid and rifampicin. Although a six-month course is standard for many forms of TB, experts frequently recommend extending the therapy to nine to twelve months for spinal TB, particularly in cases involving multiple vertebrae or significant neurological deficit.
Surgical intervention is not required for all patients but is reserved for specific, complicated scenarios. Surgery is indicated when there is a progressive neurological deficit due to spinal cord compression. Other reasons for surgery include severe, progressive spinal instability, a large abscess that requires drainage, or a severe kyphotic deformity that needs correction and stabilization. In cases with severe neurological involvement, adjunctive corticosteroid therapy may be administered for the first six to eight weeks alongside ATT.