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Spinal infections

Last updated: August 24, 2021

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Spinal infections, an umbrella term covering osteomyelitis, diskitis, and spinal epidural abscess, are a rare but serious cause of back pain. They are caused by bacteria (most commonly Staphylococcus aureus) introduced during surgery or via hematogenous or contiguous spread from other infections, which leads to inflammation and abscess formation. Risk factors include immunosuppression, bacteremia, and recent surgery. Patients typically present with nonspecific symptoms such as back pain and fever; however, the presentation depends on the location and extent of the infection and may include signs of cord compression. Diagnosis is often delayed due to the nonspecific nature of symptoms, as well as the overlap between symptoms of spinal infection and those of the underlying source of infection, e.g., skin and soft tissue infection or urinary tract infection. Diagnosis is based on blood cultures, inflammatory markers, and advanced imaging of the spine; the first-line imaging modality is MRI with and without contrast. If initial studies are negative, a CT-guided biopsy may be appropriate. Patients with hemodynamic instability or signs of neurologic compromise should be started on antibiotics immediately and urgently referred to a neurosurgeon. For stable patients, antibiotic therapy is typically deferred until the causative organism is known. Additional surgical management should be considered for patients with complications such as abscesses or spinal deformity, or who have ongoing severe pain or fail to respond to antibiotic therapy.

Epidemiological data refers to the US, unless otherwise specified.

Routes of infection

Pathogens [1][3][5]

Risk factors [1][5][6]

All types of spinal infections have similar clinical features. In cases of hematogenous spread, features of the primary infection (e.g., urinary tract infection, skin and soft tissue infection) may dominate the clinical presentation. [1][5]

  • Back or neck pain [3][4][5]
    • Onset is typically insidious, worsening over several weeks to months.
    • Occurs in a localized area
    • Worse during physical activity and at night
    • May radiate to the abdomen, hip, leg, scrotum, groin, and/or perineum
    • Severe, sharp back pain may indicate an epidural abscess.
    • Examination findings
      • Pain is exacerbated by palpation or percussion of the area.
      • Palpation of paravertebral muscles can cause tenderness and spasm.
      • Spinal mobility is reduced.
      • Neurological signs and symptoms may be present: See “Complications.”
  • Fever: present in up to 45% of patients. [5]

The diagnosis of spinal infection is often delayed because back pain is a common and nonspecific symptom, while spinal infections are rare.

Approach [5][8]

  • Obtain the following tests in all patients with suspected spinal infections:
  • If all initial tests are negative but clinical suspicion remains high, consider:
  • Suspected hematogenous or contiguous spread: Identify and treat the underlying cause.

Back pain and fever can also occur in underlying causes such as pneumonia and pyelonephritis; screen patients with spinal infections carefully to avoid missing a concurrent infection.

Laboratory studies [5]

Imaging studies [5][9]

Imaging findings may show osteomyelitis, diskitis, abscess formation, or a combination of the three.

MRI spine with and without IV gadolinium contrast [4][5][10][11]

Additional imaging studies

  • CT spine with IV contrast [1][13]
  • Nuclear medicine scans: adjunct to MRI if initial MRI results are negative or equivocal
    • Modalities: A combination of scans may be used. [5]
    • Findings: increased activity in the infected area
  • X-ray
    • Indications: not used to diagnose spinal infections but a potential initial study in a patient presenting with back pain
    • Findings [14][15]
      • Typically normal for the first 3–6 weeks of infection [5]
      • After 3–6 weeks:
        • Narrowing of disk space
        • Erosion of vertebral endplates
        • Periosteal thickening
        • Lytic lesions
        • New bone apposition
        • May show some paraspinal soft tissue changes

If imaging is inconclusive but suspicion for spinal infection persists, repeat after 1–3 weeks. [5]

CT-guided aspiration biopsy [5]

  • Confirmatory test
    • A biopsy of the affected area is performed and material is sent for microbiologic and pathologic examination.
    • Indications to repeat the biopsy include:
      • Inadequate tissue drawn
      • Specimen growing a likely skin contaminant
      • Suspected organism is hard to culture (e.g., fungi, mycobacteria, or Brucella spp.).
  • Indications

In patients with a nondiagnostic workup and negative CT-guided aspiration biopsy in whom the clinical suspicion of spinal infection remains high, a repeat biopsy (CT-guided or surgical) should be obtained. [5]

See “Differential diagnosis of acute back pain.”

The differential diagnoses listed here are not exhaustive.

The following recommendations pertain to the treatment of suspected pyogenic vertebral osteomyelitis and spinal epidural abscess. Involve specialists (infectious disease, neurosurgery) early. For treatment of tubercular vertebral osteomyelitis, see “Pott disease.”

Approach [5]

Antimicrobial therapy [5]

Empiric antimicrobial therapy for spinal infections

Diagnostics aimed at identifying the causative pathogen (e.g., blood cultures or biopsy) should be performed at the same time that empiric antibiotics are started.

Tailored antimicrobial therapy

  • Initiate IV antimicrobial treatment based on culture and susceptibility results.
  • Consider switching to oral antibiotics if symptoms improve and inflammatory markers trend downward.

Spinal infections are usually treated with 6 weeks of antibiotics, but the duration may vary based on the causative organism and patient response to treatment. Consult an infectious disease specialist prior to stopping treatment.

Invasive treatment

CT-guided drainage and irrigation [16]

Surgery

  • Indications [1][3][5]
    • Epidural abscesses and paraspinal abscesses, particularly those large in size (e.g., ≥ 2.5 cm) [1][3][17]
    • Spinal instability or deformity
    • New or progressive neurologic impairment
    • Intractable pain
    • Need for open biopsy [3]
    • Infections associated with spinal implants
    • Persistent or recurrent bloodstream infection
  • Objectives [1][5]
    • Debridement of infected tissues, with removal of prosthetic material if necessary
    • Obtaining material for microbiologic/histologic evaluation
    • Decompression of neural structures
    • Spinal fixation
    • Abscess drainage

Severe complications can occur if the diagnosis or treatment of spinal infections is delayed.

We list the most important complications. The selection is not exhaustive.

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