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Neuroradiology Case of the Week

Case 52

Ravinder Sidhu MD, Sven Ekholm MD, PhD,
and P-L Westesson MD, PhD, DDS

Clinical Presentation: Patient is a 72-year-old female post-operative status for frontal lobe glioma. An incidental finding was noted in the cervical region, which had been discussed.

Radiological Findings: Axial T2-weighted MR image showed a well-defined, oval shaped, approximately 1.5x2 cm hyperintense lesion located along the anterior margin of C2 vertebral body. It extends toward the left side causing indentation over the oropharynx (Fig. 1A). T1-weighted MR image shows the lesion to be of low signal intensity (Fig. 1B). Post-contrast MR image does not show appreciable enhancement except at its walls (Fig. 1C).

Diagnosis: Synovial/ganglion cyst

Discussion:  Cystic masses of the neck constitute a wide array of congenital and acquired lesions. The majority of cysts in newborn and infants are developmental whereas in children and adults they are inflammatory or neoplastic in nature. Some cystic lesions such as synovial/ganglion cyst, Tarlov’s perineural cysts, can mimic other lesions. Lesion location is an important determinant in formulating the differential diagnosis of a cystic neck mass.
    Synovial cysts (ganglia) generally occur in the connective tissues in relation to the peripheral joints or tendon sheaths. They also occasionally occur in the fibrous connective tissues of spine, a location initially considered to be rare. The synovial cysts usually occur in relation to facet joints of the lumbar spine. Typically, they are located dorsally in a paraspinal situation. However, they may be seen along the ventral aspect of facet joint presenting as intraspinal extradural cysts, more frequently in lumbar spine, causing nerve root/spinal cord compression. However, most of them are discovered incidentally. Intraspinal cysts can also occur in the ligamentum flavum [1,2]. Synovial cysts in cervical spine are uncommon and rarely arise within the anterior longitudinal ligament of the cervical spine simulating a retropharyngeal mass. An uncommon site of interspinous ligament of lumbar spine also has been reported [3].
    The synovial cysts usually develop as a consequence of degenerative disease of joints. Occasionally, however, no radiological evidence of spinal degeneration can be demonstrated. They can also appear as a complication of trauma. There is female preponderance and is more commonly seen in older age group. These cysts are thought to arise as herniations of the joint synovium as true synovial cysts. However, most of these cysts do not communicate with any joint cavity; therefore, it is widely believed that most of them often form as ganglia from mucinous degeneration within periarticular dense fibrous connective tissue. Histologically, the wall of synovial cyst is a lined synovial cell whereas the wall of a ganglion cyst is made of connective tissue without synovial lining cells [4,5].
    CT examination of the neck offers the advantage of superior spatial delineation and can help identifying the anatomic compartment of the lesion. MR imaging provides multiplanar capabilities, and can assist in soft tissue characterization. T2-weighted imaging can help to distinguish cystic from solid components. In addition, the use of contrast agents can also help to identify the solid components within a cyst.
    Synovial /ganglion cysts should be differentiated from Tarlov’s perineural cysts, dermoid cysts, and neuromas with cystic changes. Tarlov’s perineural cysts are extradural meningeal cysts, which are often multiple and may occur along the dorsal nerve roots at any level and these cysts usually don’t enhance. These cysts usually communicate with the subarachnoid space at some point during their development, and communication can be seen with CT myelography. Dermoid cysts are often midline in location. Neuromas with cystic changes usually show thick and nodular enhancement.

References:

1. Silverberg R. Diseases of the joints. In: Anderson WAD, Kissane JM, eds. Pathology, vol 2. 7th ed. St. Louis: CV Mosby, 1977:2041.
2. Pendleton B, Carl B, Pollay M. Spinal extradural benign synovial or ganglion cyst: case report and review of the literature. Neurosurgery 1983; 13:322-325.
3. Alguacil-Garcia A. Spinal synovial cyst (Ganglion): Review and report of a case presenting as a retropharyngeal mass. Am J Surg Pathol 1987; 11:732-735.
4. Kao CC, Winkler SS, Turner JH. Synovial cyst of spinal facet. Case report. J Neurosurg 1974; 41:372-376.
5. Kono K, Nakamura H, Inoue Y, Okamura T, Shakuda M, Yamada R. Intraspinal extradural cysts communicating with adjacent herniated disks: imaging characteristics and possible pathogenesis. AJNR Am J Neuroradiol 1999; 20:1373-1377.