a 68-year - old woman suffered from lower back and radicular pain on her right buttock and posterior calf . the patient underwent a spinal fusion due to similar symptoms three years prior to her visit . symptoms were mildly relieved after the operation but still exacerbated by standing and walking , and were only relieved when the patient was in a recumbent position . her visual analogue scale ( vas ) score for radicular pain was 7 - 8/10 . physical examination revealed no sensory disturbance in the posterior aspect of the calf , and no limited flexion or , toe - raising weakness on the right side . magnetic resonance imaging ( mri ) of the lumbar spine demonstrated l3/l4/l5 posterior fixations , a laminectomy state and diffuse disc bulging at l2-l3 and , l4-l5 . the axial mr image showed a 7  7 mm nodular lesion ( t1 , t2 low signal intensity ) at the epidural space between the l5-s1 level ( fig . 1 ) , which was revealed as gas on the computed tomography ( ct ) scan ( fig . 2a and 2b ) . the authors performed selective transforaminal epidural nerve block via the right first sacral foramen which resulted in 50% remission of the radiating pain . the authors planned to perform percutaneous needle aspiration of the gas cyst . to find the exact location of the aspiration site , 1.0 ml of contrast media was injected , with a 21 gauge epidural needle , into the epidural gas cyst via the l5-s1 posterior epidural space under fluoroscopy . contrast filling into the epidural gas cyst was confirmed by ct scan ( fig . 2c and 2d ) . by repeating the same procedure , the epidural needle was placed into the epidural gas cyst filled with contrast media under fluoroscopy . the epidural needle was slightly withdrawn and 4 ml of mepivacaine 0.5% with 5 mg of triamcinolone was instilled into the epidural space around the cyst . after the needle aspiration of the gas cyst , her vas score for lower back pain was 1 - 2/10 and the patient had almost complete resolution of radiating pain one year later . in the spine , the presence of gaseous collections or vacuum phenomenon can be found in the intervertebral disc spaces , vertebral body , and spinal canal . the incidence of the vacuum disc phenomenon increases with age , and it has been reported in approximately 50% of patients over 40 years of age . yoshida et al .   reported cases of lumbar intraspinal gas causing clinical symptoms of lumbar radiculopathy and analyzed the composition of the gas in one patient by gas chromatography , which revealed an overwhelming preponderance of nitrogen . it has been postulated that the entrapped gas formed within the degenerated vacuum disc or apophyseal joint space is extruded into a herniated disc fragment , or the epidural and paravertebral space through tears in the anulus fibrosus or the apophyseal joint ligaments . it is difficult to distinguish between gas and calcification , as both gas and calcifications display low signal on mr images . kakitsubata et al .   reported that ct discography is most helpful in establishing communication of the epidural cyst with the disc tissue . they confirmed a connection between the epidural cyst and the corresponding intervertebral disc on the ct discography visualized as a flow of the contrast material in the two cases . although connection between the epidural gas cyst and the corresponding intervertebral disc was not confirmed in this case , multilevel vacuum disc phenomenon at t12-l1 , l2-l3 , and l5-s1 was revealed . there were two former case reports referring to percutaneous ct - guided needle cyst aspiration . reported s1 radicular pain related to an intraspinal gas pseudocyst and they obtained resolution of the symptoms via needle puncture of the gas - filled cyst under ct guidance . bosser et al .   reported l5 radicular pain related to an epidural gas - containing pseudocyst . they obtained transient resolution of the radicular pain after gas aspiration via ct - guided needle puncture , but the radicular pain recurred soon after . sequential ct scan showed recurrence of the epidural gas collection , and which led to surgical treatment . to our knowledge , treatment of symptomatic epidural gas cyst by epidural block and aspiration has not yet been reported . until now , the exact pain mechanism of epidural gas cysts have not been fully explored . the first mechanism for symptom relief however as the symptoms were not completely relieved by the epidural block , we assumed that an epidural gas cyst might have a role in the space occupying the lesion . therefore , we performed needle aspiration on the epidural gas cyst , and achieved remission of the symptoms . one year later after the procedure , the patient 's vas score for lower back pain was 1 - 2 and it was controlled with intermittent analgesic medications . we think that the suspected cause of her lower back pain was related to a previous spinal surgery rather than the epidural gas cyst . we report a case of symptomatic epidural gas cyst treated with an epidural block and percutaneous needle aspiration . clinical symptoms of the epidural gas cyst can be similar to those of other more common causes of lumbar radiculopathy . the authors suggest that an epidural nerve block with needle aspiration of a gas cyst could be an alternative treatment option for patients with radicular symptoms caused by symptomatic epidural gas cyst before surgery .
a 68-year - old woman suffered from lower back and radiating pain on her right buttock and posterior calf . 
 axial magnetic resonance imaging showed a 7  7 mm nodular lesion ( t1 and , t2 low signal intensity ) at the epidural space between the l5-s1 level and computed tomography revealed it was an epidural gas cyst . 
 the authors performed an epidural block and percutaneous needle aspiration of the epidural gas cyst . 
 the patient showed almost complete resolution of symptoms one year later . 
 the authors suggest that an epidural nerve block with needle aspiration of a gas cyst could be an alternative treatment option for patients with a symptomatic epidural gas cyst before surgery .