Age / Sex : 53 / F

Chief complaint : low back pain

What is your diagnosis?

Two weeks later, you can see the final diagonosis with a brief discussion of this case (Please submit only one answer).

Courtesy : Ji Hyun Hong, Kangdong Seong-Sim Hospital

Discussion

Answer: Emphysematous osteomyelitis

Findings:

Coronal and sagittal CT scans show extensive intraosseous gas within the L5 body and sacrum. Intraosseous gas shows a bubble-like appearance. Epidural collection of air densities is seen from L5 to S1 on the sagittal CT scan. Axial CT scan reveals that air densities extend into the prevertebral space and retroperitoneum.

Contrast enhanced fat suppressed T1-weighted coronal image shows a non-enhancing area due to intraosseous gas within the L5 vertebral body and sacrum. Contrast enhanced fat suppressed T1-weighted sagittal image reveals an epidural abscess with hypointense foci of air from L4 to S1, resulting in central canal narrowing.

Differential Diagnosis: None

Discussion:

Emphysematous osteomyelitis is a rare phenomenon. Intraosseous gas in the extra-axial skeleton is rare and pathognomonic for emphysematous osteomyelitis. Intraosseous gas within the axial skeleton can be seen due to various causes including biopsy, penetrating injury, fracture, osteonecrosis, degenerative disease, neoplasm, and infection. Gas shadows in emphysematous osteomyelitis are non-localized, extensively distributed, and have a bubble-like appearance. Gas shadows usually extend into the epidural space, paravertebral space, or retroperitoneum.

The mechanism of infection is most commonly by hematogenous spread but may also relate to spread from an intra-abdominal source, from a skin or soft tissue infection, or after intra-abdominal or spinal surgery. Causative organisms include anaerobes and members of the Enterobacteriaceae family. Comorbidities, such as diabetes mellitus and malignant tumor, are common predisposing factors.

Emphysematous osteomyelitis is associated with significant morbidity and mortality. Aggressive antimicrobial therapy is required, and empirical therapy should be considered.

References:

Larsen J, Muhlbauer J, Wigger T, Bardosi A. Emphysematous osteomyelitis. Lancet Infect Dis. 2015;15:486.

McDonnell O, Khaleel Z. Emphysematous osteomyelitis. JAMA Neurol. 2014;71:512

Mahesh B, Upendra B, Vijay S, Arun Kumar G, Reddy S. Emphysematous osteomyelitis-A rare cause of gas in spine-A case report. J Spine. 2016;5:2.