Epidural abscess formation with an atypical pathogen following epidural steroid injection: A case report

Abstract

Rationale: Subcutaneous and epidural abscesses following epidural injection are a serious but rare complication. Epidural abscesses are typically caused by Staphylococcus aureus bacterial infection. In this case presented here, the causative bacterium was Enterococcus faecalis.

Patient concerns: A 67-year-old woman having chronic lower back and right leg pain with past history of 20 years of rheumatoid arthritis, diabetes mellitus, and osteoporosis (T-score: -2.7) visited the outpatient pain clinic. Magnetic resonance imaging (MRI) revealed L4-5 right central disc extrusion with inferior migration. We performed a continuous epidural block for 7 days without complications. After 10 days, she presented with worsened low back pain, erythematous skin change on the lower back, chilling, and elevated serum acute phase reactants.

Diagnosis: The diagnosis was subsequently confirmed by MRI suggesting subcutaneous and epidural abscess. Blood and pus cultures showed the growth of E. faecalis.

Interventions: Pigtail catheter drainage was performed and intravenous antibiotics (ampicillin-sulbactam) targeting E. faecalis were applied for 3 weeks. Oral antibiotics (amoxicillin/potassium clavulanate) were applied for 6 weeks after discharge.

Outcomes: At the 2-month follow-up, improvement in both the clinical condition and serum acute phase reactants levels were noted.

Lessons: Epidural injection can lead to a subcutaneous abscess that is further extended into the epidural space. One of the key factors is the presence of comorbid conditions, including diabetes mellitus and prolonged steroid usage due to rheumatoid arthritis.

Figure 1.

L-spine magnetic resonance images showing L4-L5 right central disc extrusion with inferior migration.

Figure 2.

Lumbar spine radiography after contrast injection. The contrast showed that the catheter was placed in the epidural space in the (A) anteroposterior view and (B) lateral view.

Figure 3.

Lumbar magnetic resonance images suggesting a subcutaneous epidural abscess. (A) Subcutaneous abscess (arrow) and extension to the interspinous area at L4-5 (arrowhead) in a sagittal T2 weighted image. (B) Subcutaneous abscess (arrow) and extension to the interspinous area at L4-5 (arrowhead) in a contrast-enhanced T1 weighted image. (C) Gas-containing subcutaneous abscess (arrow) in an axial T2 weighted image.

Figure 4.

Follow-up lumbar magnetic resonance images after the drainage. (A) Abscess extended to epidural space of L4-5(arrow) in a sagittal T2 weighted image. (B) Abscess extended to epidural space of L4-5(arrow) with peripheral enhancing fluid collection in a contrast-enhanced T1 weighted image. (C) Abscess of epidural space of L4-5(arrow) with peripheral enhancing fluid collection in an axial contrast-enhanced T1 weighted image. (D) Bone marrow edema of S4-5(arrowhead) in a contrast-enhanced T1 weighted image.