Intraosseous pneumatocyst is a rare condition in which a gas-filled cystic lesion of uncertain origin occupies bone
2). However, they are rarely detected in vertebral bodies, and to our knowledge, only few cases have been reported in the body of cervical vertebrae, and most of these cases occurred in the setting of spondylosis (
Table 1)
5,6,7,9). Although percutaneous injection of bone graft substitute material for treatment of a symptomatic pneumatocysts was reported as a treatment option, they are nearly always treated conservatively
1). Several authors have stated that the sizes of pneumatocysts remain stable based on radiological examinations. However, Nakayama et al.
8) reported two pneumatocysts, one in the cervical spine and the other in the lumbar spine, that spontaneously progressed to fluid-filled cysts, 6-16 months after initial presentation. Yamamoto et al.
10) reported a cervical pneumatocyst that changed to a fluid-filled cyst and that was subsequently replaced by granulation tissue, as shown by magnetic resonance imaging at 40-weeks, and Kitagawa et al.
6) reported the first enlarging pneumatocyst as determined by 16-month follow-up. To the best of our knowledge, our case of a traumatic pneumatocyst in the C6 vertebral body is the first to shown rapid resolution by 3 day follow-up CT. Although the etiology of cervical pneumatocyst is unclear, except for those associated with pathological conditions, a number of authors have hypothesized about its origins and natural courses. The gas inside a pneumatocyst is primarily nitrogen, and some authors have suggested that negative pressure within the lesion (due to some unknown mechanism) causes the release of nitrogen from surrounding soft tissues or articular joints
8,9). Gas in degenerated intervertebral discs, known as the "vacuum phenomenon", is often observed in the degenerated spine, and extension of gas from an intervertebral disc into a vertebral body through a defect in a degenerated endplate could possibly cause an intravertebral pneumatocyst
9). Furthermore, the radiolucent and osteolytic images of pneumatocysts in plain radiographs may mimic metastatic lesions. CT is the most useful radiological tool for the correct diagnosis of pneumatocysts, which exhibit no contrast enhancement on CT images. Traumatic intravertebral pneumatocysts are benign innocuous lesions that need to be differentiated from other gas-containing lesions of the spine, including those caused by osteomyelitis, osteonecrosis, or neoplasms.