929 - Intraspinal epidural cysts causing lumbar radiculopathy: Diagnostic challenges and percutaneous fluoroscopy-guided treatment - A Case Report

A 66-year-old female presented with acute low back pain radiating to the posterior right leg,numbness over the right great toe, and bilateral calf pain. Examination revealed an antalgic gait,positive seated slump test, and absent right ankle reflex, consistent with right L5/S1 radiculopathy.

CT lumbar spine demonstrated mild disc bulges at L4-L5 and L5-S1 with canal narrowing. The patient failed conservative therapy and was unable to tolerate physical therapy. She was limited in ADL’s. MRI revealed a 10-mm cystic structure in the right lateral epidural space compressing the traversing right S1 root,described as a “likely” ventral synovial cyst.

Aspiration was negative for fluid. Injection of steroid and anesthetic into the right L5-S1 facet joint produced resistance and a “pop,” suggesting rupture. A transforaminal epidural steroid injection at L5-S1 reproduced symptoms and a transient vasovagal episode. The patient reported complete resolution of pain,maintained at six weeks,and returned to baseline function without recurrence.
 

 

Discussions:

Synovial cysts account for approximately 6.5% of intraspinal lesions. While fluoroscopy-guided aspiration or rupture has shown symptomatic improvement in ~70% of patients, up to 40% ultimately require surgery. Diagnostic challenges remain, as CT often misses cysts and atypical cysts may mimic disc extrusion. Independent review by a spine interventionalist was critical in this case, as the lesion was ventral and not continuous with the facet joint, raising the differential of discal cyst vs extruded disc.
 

Conclusions:

A combined approach of facet joint injection/rupture and targeted transforaminal epidural steroid injection provided durable relief, avoiding surgery. Early MRI and proceduralist review are key to diagnosis and guiding minimally invasive management.