A1 - (d) Synovial cyst Synovial cysts are associated with a | Figure 1

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.

case examples

Example 1

A1 - The most likely diagnosis is primary synovial chondromatosis. Synovial chondromatosis is a rare monoarticular process characterized by cartilaginous bodies. Primary synovial chondromatosis has a predilection for the large joints, including the knee, hip, elbow, and shoulder...

Example 2

56YOF presents with a slowly enlarging fluctuating subcutaneous nodule about 2 cm in diameter directly lateral of the 5th Tarso-Matatarsal joint of the left foot. This developed after a rather painful experience of hyper-dorsal flexion...

Example 3

A1 - The pink arrows (images 1 and 2; 6 and 7) demonstrate a tail extending back to the joint capsule and subsheath portion of the extensor carpi ulnaris.

Imaging

Sagittal T1 weighted MRI shows a hyperintense mass (arrow) extending between the sella and suprasellar region. The differential diagnosis for this lesion includes craniopharyngioma, Rathke's cleft cyst, and arachnoid cyst.

Additional Cases

Case A

A 52-year-old man presented with a 20-minute history of chest pain radiating to the left shoulder and neck...

Case B

A 28-year-old woman presented with a 3-day history of intense pruritus over the lower back...

Case C

A 4-month-old male infant presented with skin lesions localized to the chin for the past 3 days...