"Vacuum" phenomena relate to the accumulation of gas, principally nitrogen, in crevices within the intervertebral disk or vertebra. Their appearance does not uniformly indicate "degenerative" disk disease (primary intervertebral osteochondrosis), as gaseous collections may accompany other processes (vertebral osteomyelitis, Schmorl node formation, spondylosis deformans, vertebral collapse with osteonecrosis) affecting the disk and adjacent vertebral bodies. The location and appearance of the "vacuum" phenomena are helpful indicators as to the precise nature of the spinal disorder.