Intraspinal Synovial Cyst of Facet Joint with Vacuum: a Case Report

Typical synovial cyst arising from degenerative facet joint usually appears isointense to slightly hyperintense to cerebrospinal fluid on T1-weighted and hyperintense on T2-weighted conventional magnetic resonance (MR) imaging. We present a case of intraspinal synovial cyst with thecal sac compression that manifesting low signal intensity on both T1-weighted and T2-wiehgted MR imaging due to the gas-containing nature. It may be difficult to be differentiated from crystal deposition or giant osteophyte formation if no other modality such as computed tomography is available for correlation. The entity of synovial cyst with vacuum should be included in the differential diagnoses when evaluating a patient with posterolateral epidural lesion that is hypointense at all MR pulse sequences.