Spontaneous resolution of a cervical synovial cyst

Abstract

The natural history of synovial cysts is unpredictable, and some patients experience improvement in their symptoms or stabilization without surgery. The mechanisms behind the formation and resolution of these cysts remain controversial. We report a unique case of complete and spontaneous resolution of a C7‐T1 cervical synovial cyst. A 58-year-old woman presented with persistent tingling and numbness in the medial right forearm and hand, which had lasted for 6 months. She remembered that she had experienced pain in her shoulder and arm after she had engaged in strenuous yard work, but the pain had later subsided. The tingling was located in the medial arm, the forearm, and the medial two fingers. Intermittent neck stiffness and an aching pain in the axilla were present and bothersome. She noted that she had been experiencing difficulty in using her right arm and hand when performing tasks such as opening canned jars, buttoning and unbuttoning, and handling coins. No objective motor, sensory, or reflex alterations were detected. A tentative diagnosis of C-8 nerve root irritation or carpal tunnel syndrome was entertained. Axial T2-weighted magnetic resonance (MR) images revealed a right-sided posterolateral oval epidural lesion measuring 9 6 4 mm. The lesion was contiguous with the facet joint. The MR imaging signal intensity displayed by the lesion approximated that of cerebrospinal fluid (Fig. 1 left [arrow]). A tentative diagnosis of cervical epidural synovial cyst was made and surgery was recommended. For personal reasons, the woman did not wish to submit to surgery for 6 months. At the end of that period, an updated MR imaging study was performed. A review of the images showed that the cyst had entirely disappeared (Fig. 1 right). The patient reported that her symptoms had mostly resolved and surgery was cancelled. Based on the findings on the MR images, the diagnosis of spontaneous resolution of a cervical spinal synovial cyst was made. Contemporary evidence based on experimental and clinical observations suggests that a mechanically stressed joint induces a cascade of events (upregulation and release of angiopoietin-1, interleukins-1 and -6, platelet-derived growth factor, basic fibroblast growth factor, vascular endothelial growth factor, and substance P), 1,5 resulting in synovial hyperplasia, neovascularization, and exudation of fluid (on occasion, hemorrhagic fluid), 3 and culminating in the creation of a cyst. It appears that this process is reversible because the synovial proliferation may regress on withdrawal of mechanical stress. This seems to have happened in our patient, whose curtailment of her previous mechanical activities resulted in spontaneous resolution of the cyst. A review of the recent literature leads us to infer that injection of corticosteroid medications into the facet joint may also have helped reverse this inflammatory cascade. 2