a 19-year - old patient was admitted for low back pain and radiating pain in the posterior aspect of the left leg which had begun 2 months prior . she was treated with nonsteroidal anti - inflammatory drugs , physical therapy , and an epidural block in the local hospital . she mainly complained of pain in the left leg , with a score of 6/10 on the visual analogue scale ( vas ) , and a result of 50 degrees in a passive straight leg - raising test . there were no sensory - motor abnormalities , and the tests for reflexes showed normal responses . magnetic resonance imaging ( mri ) revealed central herniation of the l4-l5 intervertebral disc , which compressed the dural sac ( fig . discectomy was suggested , as the patient complained of consistent and severe pain , the mri findings showed severe spinal stenosis , and there were no responses to conservative treatment . therefore , we decided to treat her with percutaneous epidural neuroplasty with a racz catheter on the left l5 spinal nerve root . after obtaining her informed consent , prophylactic antibiotics ( ceftezole 1 g ) were administered intravenously after negative skin test confirmation . routine monitoring equipment - including an electrocardiogram , blood pressure monitor , and pulse oximeter - were applied , and she was placed in the prone position on the fluoroscopy table . a pillow was inserted under the abdomen to correct the anteflexion of the lumbar vertebrae , the legs were abducted , and the feet were inverted . following sterile preparation and draping , the location of the sacral hiatus was confirmed by fluoroscopy , and a local infiltration of 1% lidocaine was performed in the insertion area ( 1 inch right lateral and 2 inches caudal from the sacral hiatus ) . the tip of the needle was placed between the s3 and s4 vertebrae , whose locations were confirmed by fluoroscopy with a c - arm . after confirming negative aspiration of the blood or cerebrospinal fluid ( csf ) , 10 ml of water - soluble contrast media were injected for the epidurogram . the racz catheter was inserted through the needle and was advanced towards the left l5 nerve root under continuous fluoroscopy ( fig . 2 ) . 1,500 units of hyaluronidase in 10 ml of normal saline were then injected . additional dye ( 2 ml ) was injected to confirm the contours of the nerve root , and 9 ml of 0.2% ropivacaine and 1 ml of 4 mg dexamethasone were injected following negative aspiration . the patient did not complain of severe pain , paresthesia , or unusual responses during the procedure . after 1 hour , the patient complained of sudden motor weakness in the right lower limb , on the site opposite to where the neuroplasty was conducted . the great toe dorsiflexion was marked as motor grade i , and the ankle dorsiflexion as motor grade ii . paresthesia and a dull sensation in the right l4-l5 dermatome had developed , but the patient did not complain of pain . at first , we suspected a temporary motor weakness caused by ropivacaine , and the symptoms were observed for one hour . an urgent mri was performed , but no epidural hematoma or suspicious lesions were found ( fig . around 4 hours after the neuroplasty , the motor and sensory weakness had not improved ; emergency surgery was therefore performed . discectomy of the l4-l5 intervertebral disc was conducted . during the surgery , central and left paracentral protrusions of the disc were found , and swelling of the right l5 nerve root was also discovered . after the surgery the motor strength and sensory function of the right leg had returned to normal . in the 10-day follow - up period , there were no signs of motor or sensory abnormalities , and the patient was therefore discharged without any discomfort . bleeding , infections , or nerve damage can generally develop after epidural neuroplasty , but motor and sensory weaknesses are rare complications . acute monoplegia following epidural adhesiolysis has previously been reported in a patient with failed - back syndrome and foraminal stenosis of the l4-l5 levels . however , to the best of our knowledge , there has been no report of acute motor weakness in the opposite lower extremity after percutaneous epidural neuroplasty . first , motor weakness can be caused by direct nerve injury from the epidural needle or racz catheter during the procedure . however , this was unlikely in this case , as there were no complaints of acute severe pain , sensory abnormality , or abnormal responses during the procedure . this was also unlikely in this case , as these injections cause bilateral or patchy blocks of the motor and sensory functions . fourth , although nerve damage from hypertonics can be a reason , we did not use hypertonic saline . finally , injection of a large volume of fluid into the epidural space may cause a transient neurological deficit . rocco et al .   reported that epidural injections after spinal surgery may cause complications such as cauda equine syndrome or nerve root damage as the epidural space after surgery is limited , and the injected drugs may increase the pressure and cause nerve damage either directly or by ischemia , due to decreased blood flow . they presented acute right monoplegia which had occurred after epidural adhesiolysis of the bilateral l5 nerve root in a patient with failed - back surgery syndrome , with spontaneous recovery after 5 weeks . they suggested that the large volume of fluid injection might have been the reason for the transient neurological deficit , as a compartment loculated by the fluids might have compressed the nerve . they also suggested careful injection under observation of the excretion of the contrast dye through the neural foramen in order to prevent nerve injuries caused by compression from a large volume of injected drugs . in particular , if the spinal stenosis is severe , the epidural injection may increase the pressure in the epidural space , and even a mild edema around the nerve root may cause a neurologic deficit by compression of the nerve root . we hypothesized that the large volume of fluid injected during the epidural neuroplasty and the severe spinal stenosis might have been the reason for the opposite motor weakness in this case , as per the previous reported case . the patient in the present study presented severe spinal stenosis , with a herniated disc occupying more than 2/3 of the spinal canal . the epidurogram during the neuroplasty showed a better spread of the contrast dye in the left side , and a filling defect on the right side . moreover , the central protrusion may have increased the pressure on the right side of the epidural space , and the closed compartment may have caused loculation , leading to barotrauma in the right l5 nerve root . in addition , swelling of the l5 nerve root was observed during the surgery , and the motor and sensory functions returned to normal immediately after the surgery , suggesting that the latter had a decompressive effect . however , further evaluations , including measurement of the pressure and radiologic tests , are required to prove this theory . in conclusion , we presented a rare case of unilateral motor weakness following epidural neuroplasty , on the side opposite to the lesions . the injection of a large amount of fluid during neuroplasty in a patient with spinal stenosis may cause compressive nerve damage .
recently , percutaneous epidural neuroplasty has become widely used to treat radicular pain caused by spinal stenosis or a herniated intervertebral disc . 
 a 19-year - old female patient suffering from left radicular pain caused by an l4-l5 intervertebral disc herniation underwent percutaneous epidural neuroplasty of the left l5 nerve root using a racz catheter . 
 after the procedure , the patient complained of acute motor weakness in the right lower leg , on the opposite site to where the neuroplasty was conducted . 
 emergency surgery was performed , and swelling of the right l5 nerve root was discovered . 
 the patient recovered her motor and sensory functions immediately after the surgery . 
 theoretically , the injection of a large volume of fluid in a patient with severe spinal stenosis during epidural neuroplasty can increase the pressure on the opposite side of the epidural space , which may cause injury of the opposite nerve by barotrauma from a closed compartment . 
 practitioners should be aware of this potential complication .