Discitis - Causes, Symptoms, Diagnosis, and Treatment

Introduction:

An intervertebral disc, simply known as the disc, is connective tissue supporting the vertebral column (backbone). It is present between each vertebra and holds them together. The primary function of the intervertebral disc is to act as a shock absorber for the spine and allow limited movement of the backbone. In plain X-ray images, the intervertebral disc shows a black space between the two opaque-white vertebrae, known as the intervertebral disc space.

What Is Discitis?

Discitis is an infection of the intervertebral disc space. It is a rare but serious condition that can lead to fatal consequences.

Discitis is more common in children and people aged 50 and above, thus having a bimodal distribution. Males are more frequently affected than females. An individual can have peak and down of discitis several times in their lifetime. The lower backbones are commonly affected, followed by the neck bone and the upper backbone.

What Are the Causes of Discitis?

The bacteria Staphylococcus aureus most commonly causes Discitis. Other organisms associated are Escherichia coli, Streptococcus pneumoniae, and salmonella species. Sometimes, fungi can also be involved, usually due to Candida albicans, but may affect other candida or Aspergillus species. Mycobacterium tuberculosis can also be considered the cause, especially in immunocompromised individuals.

The infection of the intervertebral space can arise from three routes, as follows,

• Direct Infection: Surgery or trauma can directly inoculate the pathogen in the disc space.

• Through Blood: Bacteria can spread through blood to cause urinary tract infections, lung infections, and other soft tissue infections. The vertebrae are the first to be affected, followed by the disc space. This is the most common route of spread in most patients.

• Spread From Nearby Structures: Localized infection from the neighboring parts caused by surgery, injection, or puncture can reach the disc space.

Some of the risk factors associated with discitis are,

• Presence of infectious bacteria in the bloodstream.

• Spinal surgeries involving catheters.

• Patients who are receiving dialysis.

• Infection in the adjacent area.

• Frequent usage of drug injections.

• Older age.

• Malnutrition.

• AIDS (acquired immunodeficiency syndrome)

• Chronic steroid usage.

• Immunocompromised condition.

• Alcohol dependence.

• Presence of cancer.

• Liver dysfunction.

• Kidney failure.

• Diabetes mellitus.

What Are the Signs and Symptoms of Discitis?

When the infection leads to inflammation of the intervertebral disc space, patients may complain of:

• Severe back pain and neck pain.

• Inability to move.

• Fever.

• Eating disorder and loss of weight.

• Muscle spasms and weakness.

• Bowel and bladder dysfunction.

• Neurologic problems.

• Abnormal spine curvature in children and they may refuse to walk.

Unresolved infection may lead to:

• Infection and inflammation of the vertebral column.

• Fusion of the vertebrae.

• Bone infection.

• Pus formation.

• Spinal deformity and paralysis.

Who Is Susceptible to Developing Discitis?

Factors that increase the likelihood of developing discitis include:

• Having an autoimmune disorder.

• Having a weakened immune system.

• Intravenous drug use.

• Recent surgery recovery.

Additionally, children under the age of 10 are at higher risk of developing this condition.

How to Diagnose Discitis?

Medical History and Physical Examination:

Physicians may interrogate details about recent surgery and debilitating diseases like diabetes mellitus to diagnose discitis early. They may also palpate the area of infection to check for tenderness and range of motion. Neurologic examination may be necessary for a few patients. Other systemic examinations may be required to locate the source of infection.

Blood Test:

The blood is investigated for ESR (erythrocyte sedimentation rate - high in reduced function of red blood cells) and CRP (C-reactive protein - a circulating protein that becomes high in inflammatory changes in the body). The ESR and CRP are often raised in discitis, and both parameters are used to assess the treatment outcome. Blood cultures are evaluated to identify the causative pathogen and guide specific antibiotic treatment.

Imaging Techniques:

• X-Rays: Plain radiographs can assess the overall alignment and stability of the vertebral column. They are also crucial in comparing pre- and post-treatment variations and are documented for follow-ups.

• CT (Computed Tomography) Scan: CT images provide finer details of the structure, and any minor abnormalities in the spinal column can be detected much earlier. The pattern of destruction in the bone-scattered bony fragments and the calcifications within the intervertebral disc space are apparent in CT images, which can be helpful before surgical planning.

• Image-Guided Biopsies: This minimally invasive method uses real-time images to sample tissues and can be performed using CT scanning.

• MRI (Magnetic Resonance Imaging): In the case of discitis, MRI is the most specific and sensitive modality for diagnosing radiological changes. The exact extent and location of the infection can be measured. MRI is functional in demonstrating the structural change and local features of inflammation that help to characterize pus-forming infections, abnormal cell growth, and spinal tuberculosis. Paraspinal muscles and spinal canal involvement can also be identified.

• Dynamic Contrast-Enhanced Magnetic Resonance Imaging (DCE-MRI): It will improve the illustration of the image and provide accurate diagnostic information.

• Bone Scintigraphy: A bone scan is a specialized radiological procedure. Small amounts of radioactive material and a tiny camera detect bone activity. In discitis, bone scans rule out metastatic lesions (cancer that has spread from a distant part of the body).

Biopsy:

A piece or sample of the inflamed tissue can be removed and evaluated under a microscope to confirm the diagnosis of discitis.

How to Treat Discitis?

• Broad-spectrum antibiotics are preferred until the culture reports arrive. Initially, it is essential for Staphylococcus coverage.

• Specific drugs for the particular pathogen should be administered once the culture report is evaluated.

• Painkillers (NSAIDs - non-steroidal anti-inflammatory drugs) are used to alleviate the symptoms.

• Bed rest and bracing (supporting device) to immobilize the vertebral column.

• Finally, surgical debridement is needed to remove the damaged tissue and prevent the infection from spreading to neighboring areas.

• It is also essential to prevent and treat infections in other body parts before they spread to the disk space.

What Is the Prognosis for Individuals With Discitis in the Long Term?

Most individuals with discitis have a good prognosis. Viral infections may heal without intervention, bacterial infections typically resolve with antibiotics, and autoimmune-related cases require focused treatment. Chronic back pain is a rare complication.

Conclusion:

Although discitis is a rare disease that can sometimes resolve on its own, there are always risky consequences associated with it. Treatment planning is also tricky because of the need for more blood to the intervertebral disc. The treatment outcome is better in children compared to adults. Early diagnosis and management are ideal for getting the best treatment results. If left untreated, it may lead to permanent deformity of the spine and the nervous system.