MR of disc protrusion engendered by infectious spondylitis

Purpose: The purpose of this study was to determine if infection- related disc protrusion formed a component of the perispinous/epidural mass in patients with intervertebral disc infection. Method: A retrospective review was undertaken of 16 consecutive patients with intervertebral disc space infection who were referred for gadolinium-enhanced MRI. Possible correlation was sought between disc infection and the presence of associated posterior disc protrusion as determined by MRI. Results: Of the 16 infected discs, 10 cases were in the lumbosacral spine, 3 in the thoracic spine, and 3 in the cervical spine. Four cases had isolated posteriorly directed disc protrusion, and 12 showed both posterior and anterior disc protrusions. The infection in patients with disc protrusion was related to Staphylococcus aureus in 14 patients, Salmonella enteritidis in 1, and Streptococcus pneumoniae in 1. Conclusion: This study showed that disc protrusion occurred in combination with disc space infections. Local factors such as the secretion by hyaluronidase from Staphylococcus aureus may play an important role in causing focal disc protrusion. The clinical importance of this finding is in the recognition that a significant part of the compromise of the spinal canal in cases of disc infection can be related to disc fragments engendered by the infectious process.