a 59-year - old man presented with a 3-month history of bilateral dorsal leg pain , which aggravated with coughing , sneezing and straining . because of these complaints , he needed a crutch for walking .
besides from diffuse loss of pin prick sensation in both lower legs , there were no deficits on neurological examination .
magnetic resonance imaging ( mri ) revealed an intradural tumor at l3l4 level , occupying the spinal canal ( fig .  1 ) and compressing the cauda equina fibers .
dura was closed using a non - resorbable running suture and was sealed with fibrin glue .
after 5  days following surgery , the patient was discharged from the neurosurgical department , without neurological deficit and without pain .
1preoperative sagittal t2-weighted mri scan of the lumbar spine showing a hyper - intense intradural tumor ( indicated by black arrowheads ) at l3l4 level occupying the complete spinal canal , with the characteristics of a schwannoma preoperative sagittal t2-weighted mri scan of the lumbar spine showing a hyper - intense intradural tumor ( indicated by black arrowheads ) at l3l4 level occupying the complete spinal canal , with the characteristics of a schwannoma three months after discharge , the patient was readmitted because of progressive low back and excruciating leg pain , radiating from the right buttock to the foot .
furthermore , there was a loss of bladder filling sensation . on examination , a subcutaneous fluctuating swelling was present at the site of previous lumbar surgery .
compression of this swelling provoked right sided leg pain and pain in the tailbone area .
furthermore , one or more cauda equina fibers appeared to herniate through a small dura defect ( fig . 
2).fig .  2postoperative t2-weighted mri of the lumbar spine in the sagittal plane ( a ) and the transversal plane ( b ) showing a large pseudomeningocele ( white arrowheads ) at l3l4 level , containing herniated cauda equina fibers ( black arrowhead ) .
white arrows indicate dura and white asterisk indicates spinal canal postoperative t2-weighted mri of the lumbar spine in the sagittal plane ( a ) and the transversal plane ( b ) showing a large pseudomeningocele ( white arrowheads ) at l3l4 level , containing herniated cauda equina fibers ( black arrowhead ) .
white arrows indicate dura and white asterisk indicates spinal canal on re - operation , a pseudomeningocele - containing multiple cauda equina fibers , herniating through a small defect in the thecal sac was identified ( fig .  3 ) .
after enlargement of the dura defect , cauda equina fibers were released and replaced intradurally . the dura was primarily closed and the pseudomeningocele was resected .
after 5  days of bed rest , the patient was discharged . at present , 6  years after re - operation , the neurological condition of the patient is excellent.fig . 
3intra - operative photograph showing opened pseudomeningocele with transdural herniation of a cluster of edematous cauda equina fibers .
the most eccentric fiber shows venous congestion and thrombosis due to incarceration intra - operative photograph showing opened pseudomeningocele with transdural herniation of a cluster of edematous cauda equina fibers .
complications of extirpation of intradural extramedullary tumors are usually related to problems with wound healing and cerebrospinal fluid ( csf ) leakage , although spinal epidural hematomas , intracranial hemorrhage due to acute reduction of csf pressure , and spinal cord injury have been described [ 1 , 12 , 13 , 15 ]
. postoperative or posttraumatic ( lumbar puncture ) csf leakage can result in pseudomeningocele formation .
a pseudomeningocele is defined as an extradural csf collection that results from a tear of the dura and subsequent csf leakage .
the majority of pseudomeningoceles result from incidental durotomy during spinal surgery , which in some cases remains unnoticed to the surgeon at the time of operation .
reported incidences vary from 0.3 to 13% in frequently performed procedures like laminectomy and lumbar disc surgery .
chiou et al .   reported four cases of csf leakage in 256 patients ( 2% ) operated for intradural tumors .
reported eight cases of csf leakage ( 6% ) and six ( 5% ) pseudomeningocele formations in 128 patients operated for spinal schwannoma .
management of iatrogenic pseudomeningoceles and csf fistulas usually begins with bed rest , followed by external lumbar drainage for several days .
drainage for 35  days has a success rate over 90% in the treatment of csf leakage , but harbors a risk of infection .
a rare , but potentially devastating complication of iatrogenic csf leakage is entrapment and incarceration of nerve roots at the site of the dura defect [ 3 , 5 , 79 , 13 ] .
this can cause irreversible nerve damage through strangulation and may lead to permanent neurological deficit .
so far , only nine cases of nerve root entrapment into an iatrogenic pseudomeningocele have been described . in only one of these cases , mri was available to preoperatively establish the diagnosis .
all cases were re - operated , which resulted in complete recovery in six cases . in three patients ,
typically , on re - operation herniated nerve roots were replaced intradurally and the dura was closed , either primarily or with a dura graft ( table  1 for details).table  1data of nine cases of nerve root herniation into iatrogenic pseudomeningocelenumberauthorage / sexinitial operationintervalsymptomssurgical findingsoperative result1hadani 55/mlam l4 , l514  dl5 paindorsal dura defect , nerve root herniation and strangulationrecovered2hadani 41/mdisc l5s15  yl5 paindorsal dura defect , nerve root herniationrecovered3hadani 41/mlam l3l53  yl4s1 sm and paindorsal dura defect , nerve root herniation and strangulationl5 m4kothbauer 60/fdisc l4l51  dl5 sm and painventral dura defect , cauda equina herniationrecovered5nishi
63/mdisc l3l4 , lam l4 , l59  ds1 painunspecified dura defect , nerve root herniationrecovered6oconnor 16/fdisc l4l58  yl5 s and paindorsal dura defect , nerve root herniationrecovered7pavlou
l4l55  ds1 painventral dura defect , nerve root herniations1 sm9tppich 78/mdisc l4l54  dl5 s and painventral dura defect , nerve root herniationl5 mm male , lam laminectomy , l lumbar , d day , disc discectomy , s sacral , y year , sm sensory and motor deficit , f female , bilat bilateral , m motor deficit , s sensory deficit data of nine cases of nerve root herniation into iatrogenic pseudomeningocele m male , lam laminectomy , l lumbar , d day , disc discectomy , s sacral , y year , sm sensory and motor deficit , f female , bilat bilateral , m motor deficit , s sensory deficit transdural herniation and entrapment of cauda equina fibers into a pseudomeningocele has not been reported before in the literature . in our present case ,
four weeks later , during an episode of coughing and sneezing , sudden radicular pain occurred in the right leg and progressive pain in his tailbone . the pain became worse , and also problems with micturition occurred .
it is most likely that the dura defect initially was plugged with cauda equine fibers .
a sudden increase of intrathecal pressure during coughing and sneezing caused herniation of the cauda fibers and entrapment into the relatively small dura defect . entrapment resulted in venous congestion of ( part of ) the nerve roots and caused incarceration ( fig . 
this case underlines the importance of meticulous dura closure , especially in the light of potentially permanent neurological deficit that can be caused by strangulation of neural tissue in the dura defect .
as the literature shows , this serious complication can occur many years after the initial surgery .
fortunately , our patient made an excellent recovery after reduction of cauda equina herniation and repair of the dura defect . in case of ( acute )
new nerve root or cauda equina signs and/or symptoms after spinal ( intradural ) exploration , the clinician should be aware of the possible existence of transdural nerve fiber entrapment . mr imaging is the technique of first choice to detect this rare , treatable , but potentially devastating complication of incomplete spinal dura closure .
 incidental or intentional durotomy causing cerebrospinal fluid ( csf ) leakage , leading to the formation of a pseudomeningocele is a known complication in spinal surgery . 
 herniation of nerve roots into such a pseudomeningocele is very rare , but can occur up to years after initial durotomy and has been described to cause permanent neurologic deficit . 
 however , cauda equina fiber herniation and entrapment into a pseudomeningocele has not been reported before . here , 
 we present a case of symptomatic transdural cauda equina herniation and incarceration into a pseudomeningocele , 3  months after extirpation of a lumbar schwannoma . 
 a 59-year - old man , who previously underwent intradural schwannoma extirpation presented 3  months after surgery with back pain , sciatica and loss of bladder filling sensation caused by cauda equina fiber entrapment into a defect in the wall of a pseudomeningocele , diagnosed with magnetic resonance imaging . on re - operation , the pseudomeningocele was resected and the herniated and entrapped cauda fibers were released and replaced intradurally . 
 the dura defect was closed and the patient recovered completely . in conclusion , csf leakage can cause neurological deficit up to years after durotomy by transdural nerve root herniation and subsequent entrapment . 
 clinicians should be aware of the possibility of this potentially devastating complication . 
 the present case also underlines the importance of meticulous dura closure in spinal surgery . 
Case report
Discussion