An Unusual Presentation of a Lumbar Synovial Cyst

STUDY DESIGN: A case of intraforaminal synovial cyst is reported. OBJECTIVES: To stress the importance of the way intraforaminal synovial cyst, a very rare condition, causes a peculiar position of the nerve root in the foramen and to describe the required surgical approach. SUMMARY OF BACKGROUND DATA: Intraforaminal synovial cyst is a highly unusual finding. The existence of this rare entity raises the problem of differential diagnosis with other space-occupying lesions of the neural foramen, such as herniated disc, neurinoma, neurofibroma, and metastatic lesions METHODS AND RESULTS: A 64-year-old woman suffered a right L4 radiculopathy with motor deficit. Computed tomography showed a space-occupying lesion in the L4-L5 foramen isodense with the disc. Magnetic resonance images showed a right intraforaminal cystic lesion at the L4-L5 level with no enhancement after intravenous infusion of gadolinium. A 3-cm cystic lesion, which appeared to arise from the L4-L5 facet joint without direct communication, was excised from the L4-L5 foramen. In contrast with intraforaminal disc herniation, downward displacement of the L4 nerve root was observed. Two months after surgery, the patient was pain-free and neurologic examination revealed no motor deficit. CONCLUSIONS: An unusual intraforaminal presentation of a lumbar synovial cyst demonstrates the importance of considering this entity and of adapting the surgical technique to avoid injury to the nerve root.