Intraspinal synovial cysts are infrequent causes of back and radicular leg pain. Commonly associated with degenerative spinal disease, the majority of synovial cysts appear in the lumbar spine. Rarely, intracystic hemorrhage can occur through an unclear mechanism. Similarly rare, cysts may also become migratory. The pathogenesis of hemorrhagic synovial cysts remains uncertain and their potential for migration also remains unclear. A 36 year-old male presented to the clinic with 5 months of back pain and leg pain that began after a work-related injury. An initial MRI obtained by another surgeon 3 month prior demonstrated an epidural cystic mass with T1 hypointensity and T2 hyperintensity at L2-L3. With worsening pain, the patient came to our clinic for a second opinion. A second MRI demonstrated resolution of the L2-L3 epidural cystic mass and formation of a new epidural cystic mass at L3-L4 causing compression of the thecal sac. The patient subsequently underwent decompressive hemilaminectomy with cyst removal. We present a case of two lumbar synovial cysts, separated over time and a vertebral level and giving the appearance of a single, migratory cyst. This is the first case of an "occult migratory" synovial cyst with repeat MR imaging capturing spontaneous resolution of the initial cyst and formation of a hemorrhagic cyst one level below. We also present a summary of the 44 cases of hemorrhagic synovial cysts reported in the literature and propose a mechanism that may account for the hemorrhagic and migratory progression in some patients.
Keywords: hemorrhagic; juxtafacet cyst; lumbar synovial cyst.