Disc degeneration or spondylosis, when severe, may lead to the development of a vacuum phenomenon in the spine caused by gas production. This gas is visible on plain X-ray films, and is even more clearly apparent on computed tomography (CT) imaging, but may not be apparent on MRI. We present the case of a 69 year-old female with MRI appearing to exhibit a significant L4-5 disc herniation that, on further imaging with CT, was determined to be air in the epidural space without disc herniation. The importance of correlating clinical presentation, neurologic examination, and multimodal imaging is stressed.

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