This 44-year-old male presents with back and right leg pain. Take a look at the first two images without arrows before looking at the duplicate images with arrows.
Q1 – The most likely diagnosis is:
(c) Epidural lipomatosis
(d) Synovial cyst
A1 – (d) Synovial cyst
Synovial cysts are associated with arthropathic facet joints, and rise near the joint articulation.
They are most common in the lumbar region, but can occur in the cervical region occasionally and thoracic rarely. L4-5 and L3-4 are the most common sites.
Neurally-based root sheath cysts show an intimate relation to the adjacent nerve root.
Percutaneous drainage has a high recurrence rate. Surgical resection is usually required, but due to adherence of the synovial tissue to the dura, it may be complicated by cerebrospinal fluid leak.
Synovial cysts often contribute to compressive radiculopathy. Sometimes they may prolapse posteriorly out of the spinal canal.
Gas within the cyst is pathognomic for synovial cyst and may be seen in the absence of infection. Cysts may be hemorrhagic, and contain debris contributing to a complex imaging appearance with variable T1 signal.
Synovial cysts are often proteinaceous or hemorrhagic, and therefore not always darker than muscle on T2.
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1. Bjorkkengren AG. Symptomatic Intraspinal Synovial Cysts. AJR 1987; 149(1):105-107.