Far lateral extraforaminal lumbar synovial cyst: Report of two cases

OBJECTIVE AND IMPORTANCE: We present two cases of a far lateral extraforaminal synovial cyst at the L5-S1 level of the spine. Neither case was diagnosed as a synovial cyst before surgery because of their atypical location. Only one other case of an extraforaminal synovial cyst, located at L4-L5, has been reported in the literature. CLINICAL PRESENTATION: Both women presented with radicular leg pain and examination findings consistent with L5 root compression. INTERVENTION: During surgery, the cyst was not associated with the facet joint. One cyst was adherent to the nerve root. Both cysts were completely resected, with excellent pain relief. CONCLUSION: These cases serve as a stimulus to look outside the spinal canal and foramen in patients with symptoms suggesting nerve root compression. Far lateral extraforaminal synovial cyst should be included in the differential diagnosis.