Paraspinal abscess communicated with epidural abscess after extra-articular facet joint injection

Abstract

Facet joint injection is considered to be a safe procedure. There have been some reported cases of facet joint pyogenic infection and also 3 cases of facet joint infection spreading to paraspinal muscle and epidural space due to intra-articular injections. To the author's knowledge, paraspinal and epidural abscesses after facet joint injection without facet joint pyogenic infection have not been reported. Here we report a case in which extra-articular facet joint injection resulted in paraspinal and epidural abscesses without facet joint infection. A 50-year-old man presenting with acute back pain and fever was admitted to the hospital. He had the history of diabetes mellitus and had undergone the extra-articular facet joint injection due to a facet joint syndrome diagnosis at a private clinic 5 days earlier. Physical examination showed tenderness over the paraspinal region. Magnetic resonance image (MRI) demonstrated the paraspinal abscess around the fourth and fifth spinous processes with an additional epidural abscess compressing the thecal sac. The facet joints were preserved. The laboratory results showed a white blood cell count of 14.9 x 10(9) per liter, an erythrocyte sedimentation rate of 52 mm/hour, and 10.88 mg/dL of C-reactive protein. Laminectomy and drainage were performed. The pus was found in the paraspinal muscles, which was communicated with the epidural space through a hole in the ligamentum flavum. Cultures grew Staphylococcus aureus. Paraspinal abscess communicated with epidural abscess is a rare complication of extra-articular facet joint injection demonstrating an abscess formation after an invasive procedure near the spine is highly possible.

Fig. 1

(A) Sagittal T2-weighted magnetic resonance image (MRI) showing an epidural mass compressing the thecal sac between the laminae of L4 and L5. (B) Gadolinium-enhanced MRI showing peripheral enhancement of the mass in the paraspinal muscle.

Fig. 2

Axial MRI showing a mass of hyperintense signal intensity on T2-weighted image (A) and isointense signal intensity to the spinal fluid on T1-weighted image (B). Gadolinium-enhanced axial MRI showing a mass of high-signal peripheral rim enhancement with a low-signal at the core with expansion of the inflammation into the epidural space (C). There is no involvement of facet joints.