Teaching Case

Painful numbness of both hands, loss of muscular strength of the upper limbs and fatigability of the lower limbs. Paraparesia, predominating on the right side.

The patient consulted for painful numbness of both hands, loss of muscular strength of the upper limbs and fatigability of the lower limbs.
Clinical examination showed mild paraparesia, predominating on the right side.
Imaging findings were suggestive of intraspinal synovial cyst, which was confirmed at surgery.

Juxta-articular cysts are found around any synovial-lined joint. They are called true synovial cysts, when synovial-lined, or ganglion cysts, when there is no synovial lining. Synovila lining depends on whether they are in communication with adjacent joint, or not. A spinal location is uncommon. The accepted pathogenesis of these lesions is excessive joint mobility with herniation of the synovium through the degenerative joint capsule. This explains why intraspinal synovial cysts are found in about 75% of cases at the level of L4-L5, being the most mobile segment of the spine and the most common location of degenerative disease. The second most common location of synovial cysts in the spine are, with equal incidence, the levels L3-L4 and L5-S1. Cervical and thoracic locations are rare. In the cervical spine, the mobile lower segments may be involved. Only 5 cases occurring at the level C1-C2 have been reported. Anatomically these synovial cysts are in close relation with the ligamentum flavum and always adjacent to degenerative interapophyseal joints. Their content is variable, as clear fluid gas, calcium or hemorrhagic components can be found. Conventional radiographs show degenerative changes with involvement of the apophyseal joints. True or pseudo-spondylolisthesis may coexist. At myelography, an extradural impression on the postero-lateral border of the thecal sac is observed. CT scan may be diagnostic by demonstrating an extradural, round mass located on the anterior border of a degenerative apophyseal joint, with central CSF-like fluid or gas. The periphery of the cyst may be hyperdense or calcified. Arthrography or arthro-CT scan can be useful, showing a communication with the apophyseal joint. Percutaneous injection od steroids can be performed as a therapeutic option. MRI best evaluates the content of the cyst and depicts the relation between the lesion and the adjacent ligamentum flavum and thecal sac. Contrast enhancement is seen in cases of inflammatory changes. The main differential diagnoses are migrated herniated disc, which is usually lobulated, perineural cyst, which is in close relation to nerve root, schwannoma, which shows no low signal capsule on MRI, and hematoma.