IS case 454: Juxta-articular cyst
Imaging Sciences URMC 2010
Publication Date: 2010-08-30
There was an 1.2 x 1.1 cm extradural lesion which followed CSF fluid signal intensity, T1 hypointensity (Fig. 1) and T2 hyperintensity (Figs. 3 & 4), in the left aspect of the central canal at the L4-L5 level. The lesion appeared to communicate with the facet joint and there was degenerative facet hypertrophy at this level (Fig. 4). With the exception of L5-S1, the remaining intervertebral disc space heights and the signal intensities of the discs were normal. Pre and paravertebral soft tissues were unremarkable.
The majority of juxta-articular cysts occur in the lumbar region, most commonly at L4-L5. They are associated with degenerative facet arthropathy and so they characteristically appear as an extradural round mass arising from the joint either in the posterolateral region of the spinal canal or in the paraspinal soft tissues (Fig. 4). Patients may experience radicular pain or other neurologic deficits depending on the location and size of the cyst.
Most cases are lined by synovium and are called synovial cysts. A minority are instead lined by a fibrous capsule and do not directly communicate with the facet joint (ganglion cysts). At MRI, both may demonstrate signal characteristics typical of simple cysts (central T2 hyperintensity and T1 hypointensity) unless they contain mucin or hemorrhagic fluid. They may also present with peripheral calcifications or enhancement.
Recognizing distinctions between synovial and ganglion cysts by imaging is usually not possible and not important clinically because the treatment is the same . The main differential to consider is extruded disc material or a nerve sheath tumor.
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