📌 Facet Synovial Cyst

https://youtube.com/shorts/Ph09YQELH_4

 

A facet synovial cyst is an extradural cystic lesion arising from a degenerated facet (zygapophyseal) joint, most commonly in the lumbar spine. 

Rather than a simple fluid collection, it represents a dynamic degenerative process of the posterior elements and should prompt careful imaging-based characterization.

 

Clinical 

• May be incidental and asymptomatic.
• When symptomatic, commonly causes radiculopathy or neurogenic claudication due to lateral recess or foraminal compression.
• Clinically relevant because its presence should trigger evaluation for underlying or dynamic instability, especially when intervention is considered.

 

Look beyond the cyst

Even without overt listhesis on supine MRI, assess for:

• Facet effusion
• Degenerative spondylolisthesis
• Segmental alignment
  Because a synovial cyst doesn’t prove instability—but it should make you look for it.

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Imaging Evaluation

1) Facet-centered origin (most important)

• Rounded or ovoid extradural lesion
• Intimate continuity with a degenerated facet joint (± visible stalk)
• Supportive findings:

2) Location and neural compression

• Lateral recess (most common): traversing nerve root compression
• Neural foramen: exiting nerve root compression
• Posterior/paraspinal extension: confirms facet origin, often less symptomatic

3) Size and mass effect

• Usually small, most often < 22 mm
• Report:

4) Signal characterization — not always a “simple cyst”

• Simple (serous)
• High-protein / viscous
• Hemorrhagic
• Vacuum (gas)
• Calcified

https://youtu.be/8GW7WNHkzx0