Spondylodiscitis is a serious infectious disease affecting the spine, targeting the intervertebral disc and adjacent vertebral bodies. It combines discitis (inflammation of the disc space) and spondylitis (inflammation of the vertebrae). Although not common, the infection’s location requires immediate medical attention to prevent severe complications. Early diagnosis and a comprehensive treatment plan are necessary to manage the infection and preserve spinal integrity.
Understanding Spondylodiscitis
The pathology involves the destruction of normal spinal architecture by invading microorganisms. In adults, the infection typically begins in the highly vascularized subchondral bone of the vertebral endplate. From there, the infectious process spreads into the intervertebral disc space and then to the neighboring vertebral body. The intervertebral disc is largely avascular in adults, meaning it lacks a direct blood supply, making it difficult for immune cells and systemic antibiotics to reach the site of infection effectively.
In contrast, children possess a vascular network within their discs, often leading the infection to start directly in the disc tissue before moving to the adjacent bone. The resulting inflammation and bone destruction lead to osteomyelitis, causing instability and significant pain. This destructive process can be acute (rapid onset of severe symptoms) or, more commonly, subacute or chronic, developing slowly over several weeks to months.
Sources of Infection and Risk Factors
The spine most frequently becomes infected through hematogenous spread, where bacteria travel through the bloodstream from a distant site. Common primary sources include infections of the urinary tract, skin, or respiratory system, as well as endocarditis. Less commonly, infection is introduced directly through penetrating trauma, spinal surgery, or contiguous spread from adjacent soft tissue infection. The most common infectious agent is Staphylococcus aureus, which accounts for a large percentage of pyogenic (pus-forming) spondylodiscitis cases.
Other pathogens, such as Escherichia coli and Mycobacterium tuberculosis (which causes Pott disease), can also cause the condition. Several predisposing factors increase susceptibility, including conditions that compromise the immune system, such as diabetes mellitus, cancer, and HIV, or the long-term use of immunosuppressive medications like steroids. Advanced age, intravenous drug use, and a history of recent invasive medical procedures, including spinal injections or surgery, also elevate the risk.
Recognizing Symptoms and Confirming Diagnosis
The clinical presentation of spondylodiscitis can be non-specific, which often leads to a delay in diagnosis. The most consistent symptom is severe, localized back pain, present in over 90% of patients, and frequently worsens at night or with movement. Unlike typical mechanical back pain, this pain is often constant and not relieved by rest or common pain medications. Systemic signs like fever and chills are less consistently observed, sometimes occurring in fewer than half of patients, which can obscure the diagnosis.
In advanced cases, neurological deficits may develop if the infection leads to an epidural abscess or spinal cord compression. These deficits can manifest as numbness, weakness, or radiating pain into the limbs. The diagnostic process begins with laboratory tests to identify signs of infection and inflammation, primarily looking for elevated levels of erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP). Blood cultures are also collected, though they may not always identify the causative organism.
Imaging studies are crucial for confirming the diagnosis and assessing disease extent. Magnetic Resonance Imaging (MRI) is the most reliable tool, offering high sensitivity and specificity for detecting early signs of infection in the disc and bone marrow. While X-rays and Computed Tomography (CT) scans show bone destruction and disc space narrowing in later stages, they are less useful for early detection. If blood cultures are negative, a CT-guided biopsy is often performed to obtain a tissue sample, which is necessary to identify the specific pathogen and guide targeted antibiotic therapy.
Medical Management Strategies
Treatment for spondylodiscitis is prolonged and requires a multidisciplinary approach involving spine specialists and infectious disease experts. The primary goal is to eradicate the infection while stabilizing the spine and managing pain. Antibiotic therapy is the mainstay of treatment, often starting with broad-spectrum antibiotics until culture results are available. Once the specific pathogen is identified through biopsy or culture, the regimen is narrowed to a targeted medication.
The antibiotic treatment duration is long, often lasting six to twelve weeks, to ensure complete clearance of the infection from the bone and disc tissue. Spinal immobilization, using a rigid brace or temporary bed rest, is employed to reduce pain and prevent further damage or vertebral collapse. The patient’s response is monitored through regular clinical evaluations and checks of inflammatory markers like CRP and ESR.
Surgical intervention is reserved for specific situations where conservative management fails or complications are present. Indications for surgery include:
- Development of a neurological deficit.
- Evidence of significant spinal instability or deformity.
- Presence of a large abscess.
- Failure of prolonged antibiotic therapy.
The procedure typically involves debridement to remove infected tissue, decompression to relieve pressure on the spinal cord or nerves, and often, spinal fusion to stabilize the affected segments. The prognosis is generally favorable with timely management, though recovery requires diligent follow-up care.