Vacuum phenomenon is not uncommonly seen in degenerated lumbar discs. However, we have not seen any reports of lumbar nerve compression associated with intradural gas formation.The case study centered on a 66 year old male patient with a one year history of pain involving the left lateral thigh and in whose case conservative treatment had been unsuccessful. Preoperative plain lumbar radiographs showed deformation and narrowing of the intervertebral discs, while MRI and CT revealed gas formation in the intradural spaces at the L2-L5 intervertebral discs. During surgery, a gas containing tumor which had adhered to the cauda equina was observed. Moreover, it had conjucted to the intervertebral disc at L2-L3. After surgery, the patient recovered well. In this case, gas formation in the degenerated intervertebral disc migrated into the intradural space and caused nerve compression.The CT findings were useful in diagnosis due to the low intensity area being clearly visible.