intraosseous pneumatocyst

Intraosseous pneumatocysts are gas-containing cystic structures seen inside the bone.

Pathology

They are of uncertain etiology. These cysts do not communicate with the joint.

Location

Most common site of involvement is sacroiliac joints. Other sites involved are cervical spine, scapula and other bones rarely.

Radiographic features

CT

Appear as very low density (i.e. air at approximately -1000 HU) cystic lesion with thin sclerotic margin, usually abutting a joint.

MRI

Low signal intensity on both T1 and T2 weighted MR images.

Differential diagnosis

Imaging differential considerations include:

• osteomyelitis from gas-producing organism
• osteoblastic metastases on MRI
• osteonecrosis

Practical points

• There is a risk of erroneously misdiagnosing intraosseous lipomas as intraosseous pneumatocysts, or vice-versa, if the lesion is only eye-balled on a soft tissue window. Therefore if unsure, one should either measure an ROI of the lesion to clarify if gas or fat density, or review the lesion on a lung window.

See also

• vertebral pneumatocyst

Siehe auch:

• Osteomyelitis
• osteoblastische Knochenmetastasen
• Aseptische Wirbelkörpernekrose
• intraossäres Ganglion
• intraossäres Gas
• Pneumatozyste Wirbelkörper
• emphysematöse Osteomyelitis