What causes vacuum disc sign in the spine on imaging?
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Answer:
The vacuum disc sign is caused by the accumulation of gas, mainly nitrogen, within the intervertebral disc space. It is most commonly seen in degenerative disc disease where structural disc damage leads to clefts or fissures within the disc. This finding is associated with spinal segmental instability and may correlate with chronic low back pain or symptoms of nerve root compression. It can also be seen in vertebral collapse due to benign or malignant causes.
Why is it called so?
The name “vacuum disc sign” refers to the radiologic appearance of a gas collection within the intervertebral disc space that appears as a radiolucent area on plain radiographs or CT scans. The term “vacuum” describes the relative negative pressure inside degenerated discs that allows dissolved gases from surrounding tissues to accumulate and become visible.
Pathophysiology
Degeneration of the intervertebral disc leads to fissures and clefts forming in the nucleus pulposus and annulus fibrosus. With spinal movement, the pressure within the disc space fluctuates, increasing when vertebrae approximate and decreasing when they distract. This drop in pressure creates a suction effect, drawing out dissolved gas (mostly nitrogen) from adjacent tissues into the disc fissures, resulting in a visible gas collection known as the vacuum phenomenon.
Alternative names:
Vacuum phenomenon in the spine
Other associated named signs:
None specific; may be associated with signs of degenerative disc disease and vertebral collapse.
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