Epidural Abscess & Vertebral Osteomyelitis

Spinal epidural abscess can be difficult to diagnose. Fever and back pain should raise suspicion for epidural abscess and prompt urgent imaging to rule it out. Fever is not universally present, so a high index of suspicion is required, especially in patients with leg weakness, loss of sensation, or loss of bowel/bladder control. Timely recognition with emergent surgical consultation is crucial to avoid complications such as paralysis, sepsis, or both. Vertebral osteomyelitis is another cause of back pain and infection that may present with accompanying epidural abscess or alone. Causative organisms are similar to those of epidural abscess.

Epidural Abscess

Predisposing Conditions

Patients often (but do not always) have one or more of the following conditions:

• diabetes

• alcoholism

• HIV

• spinal abnormality or trauma (including surgery, drug injection, or catheter placement)

• local or systemic infection

Causal Pathogens

• Staphylococcus aureus causes about 66% of spinal infections.

• Other causes include the following:

  • coagulase-negative staphylococci, such as Staphylococcus epidermidis

  • gram-negative bacteria, particularly Escherichia coli (usually subsequent to urinary tract infection) and Pseudomonas aeruginosa (especially in injection-drug users)

  • in rare cases, anaerobic bacteria, actinomycosis or nocardiosis, mycobacteria, fungi, or parasites (Echinococcus and Dracunculus)

Complications

Bacteria can spread to the epidural space via contiguous spread or hematogenous dissemination and can cause systemic complications as demonstrated in the following figure:

(Source: Spinal Epidural Abscess. N Engl J Med 2006.)

Diagnosis

• full history plus physical examination

• complete blood count (CBC), erythrocyte sedimentation rate (ESR), C-reactive protein (CRP)

• blood cultures

• urine cultures and chest radiography if other sources of infection are suspected

• MRI (the imaging modality of choice)

• CT myelography (also highly sensitive but more invasive and reserved for patients with MRI contraindications; requires analysis of cerebrospinal fluid [CSF])

• no routine lumbar puncture (often adds little to diagnosis and is associated with a slight potential risk)

The following table offers common pitfalls and recommended approaches in diagnosing and treating spinal epidural abscess:

(Source: Spinal Epidural Abscess. N Engl J Med 2006.)

Management

Spinal epidural abscess is generally managed with emergency decompressive surgery and antibiotics. However, if a patient refuses surgery, has high operative risk, or has already had extended duration of paralysis, management with antibiotics can be considered.

Vertebral Osteomyelitis

Vertebral osteomyelitis is another cause of back pain and infection that may present with accompanying epidural abscess or alone. Causative organisms are similar to those of epidural abscess. Suggested antibiotic regimens for common causes are provided in the following table:

(Source: Vertebral Osteomyelitis. N Engl J Med 2010.)