it is hard to distinguish symptomatic spinal stenosis ( ss ) from asymptomatic ss in case of patients with radiological multiple stenosis .
especially , the diagnosis of foraminal and extaforaminal stenosis at l5-s1 is also difficult because of bony and ligament structures surrounding this level4 ) .
many radiological modalities were reported to diagnose foraminal and extraforaminal stenosis at l5-s1 , such as computed tomography ( ct ) , magnetic resonance image ( mri)8,9,11 ) , magnetic resonance myelography ( mrm)6 ) and so on .
if some diagnostic modalities have high concordance between clinical symptoms and radiologic findings , these have high sensitivity for diagnosing foraminal and extraforminal stenosis at l5-s1 .
the purpose of this study is to evaluate the usefulness of the new diagnostic technique of principles of the selective excitation technique mri ( proset - mri ) to know and suggest the precise radiologic findings that can prove symptomatic stenosis at l5-s1 .
twenty - eight patients ( 15 men , 13 women ; mean age , 60.010.0 years ; range 36 - 74 years ) with foraminal and extraforaminal stenosis at l5-s1 , who underwent decompressive surgery or selective nerve root block ( snrb ) in the author 's hospital between november 2009 and june 2011 , were included in this study .
we performed mri , inclusive of 3-dimensional coronal fast - field echo ( ffe ) sequences with selective water excitation using the proset . to have images of lumbosacral nerve roots and dorsal root ganglion ( drg ) ,
the setting of imaging plane is parallel to the longitudinal axis of the lumbosacral spinal canal . for image processing , an aquarius 3d work station equipped with commercially available automated analysis 3d rendering software ( terarecon inc .
the change of symptomatic l5 nerve root was revealed by root swelling ( rs ) ( fig . 1 ) and
2 ) . swelling and indentation of the nerve roots were evaluated on 3d mr rendering images of the lumbosacral spine .
interobserver variability of the nerve root swelling and indentation was assessed by using the  statistics .
a  value of less than 0.40 indicated poor agreement ; 0.41 to 0.60 , moderate agreement ; 0.61 to 0.80 , substantial agreement ; and 0.81 or greater , almost perfect agreement .
comparison of pre - treatment pain with post - treatment pain was taken by visual analogue scale ( vas ) scores .
seven of the 26 cases were excluded from the study because 2 decompressive surgeries and 2 snrb cases were not evaluated for vas scores , and 3 snrb cases were dropped due to follow - up loss .
all of the including cases were taken pre - treatment proset - mri , which also revealed nerve root swelling and/or indentation .
according to the meaningful proset - mri findings of symptomatic stenosis , the pre- and post - treatment vas have a statistical significance ( p<0.01 ) at the rs and indentation .
however , comparison with proset - mri cases combining rs with indentation do not have any statistical significance ( p=0.025 ) ( table 2 ) . according to the treatment modalities ,
there are 4 patients ( 2 men , 2 women ; mean age , 62.38.1 years ; range 56 - 74 years ) . on the proset - mri ,
3 cases revealed nerve root swelling and indentation , and 1 case revealed only nerve root swelling .
two cases were added postoperative one - month proset - mri , which revealed diminished nerve root swelling , but indentation was resolved partially ( fig .
in addition , vas scores of these patients reduced from 5.50 to 2.75 ( p<0.01 ) after over 3 months of a follow - up period . on the snrb case ,
there are 15 patients ( 9 men , 6 women ; mean age , 62.26.6 years ; range 50 - 71 years ) . on the proset - mri ,
11 cases revealed only nerve root swelling , and 4 cases revealed only indentation of the nerve root , but there is no case that reveals combining nerve root swelling with indentation .
further , vas scores of these patients reduced from 5.40 to 1.87 ( p<0.0001 ) after a 3-month follow - up period ( table 3 ) .
agreement with respect to the recognition of nerve root swelling and indentation was excellent ( =0.86 and 0.78 ) .
according to the conventional mri , central and lateral stenosis can be seen easily . unlike central and lateral stenosis
, the diagnosis of foraminal and extraforaminal stenosis at l5-s1 is very difficult and vague .
that is often caused by the narrow space between l5 transverse process and sacral ala .
these pathologic conditions were described as the term , such as far - out syndrome , lumbosacral tunnel , lumbosacral bony tunnel ( lsbt)3,4 ) , and so on .
although many clinicians think there is no doubt that foraminal or extraforaminal stenosis at l5-s1 is diagnosed via the conventional mri2 ) , such patients do not complain of severe stenotic symptoms .
many studies were reported to diagnose foraminal and extraforaminal stenosis at l5-s1 precisely and many clinicians tried to match up patient 's symptoms with radiologic findings .
lee et al.8 ) reported that reliable conventional mr findings of extraforaminal with or without foraminal disk herniation are focal eccentricity of the disk contour , obliteration of the epidural fat surrounding the nerve root , change in the thickness of the nerve root , and displacement of the nerve root .
however , there are many cases of incorrect diagnoses or unmatched clinical and radiological findings .
moon et al.9 ) studied the reliability of mri findings in detecting symptomatic lesions and they reported the most reliable findings of symptomatic lesions , which is the focal eccentricity of the disc .
however , this study has a limitation of confirming the symptomatic lesion owing to not adding and comparing with the other imaging protocols .
nakao et al.10 ) also studied to diagnose the extraforaminal stenosis at the lumbosacral junction .
they used 3-dimensional ct imaging of lsbt surrounding the l5 transverse process , l5 vertebral body , and sacral ala at the extraforaminal lesion .
mrm provides the precise coronal images that are close to the operative views , and two useful findings are drg swelling and abnormal running course of l5 exiting nerve root .
however , this study had low sensitivity to detecting the meaningful findings of mrm , such as drg swelling and running course abnormality .
in addition , heo et al.5 ) also studied using an oblique mri that is parallel to the connecting the posterior margin of the upper to lower endplate of the affected level 's functional segmental unit . through this mr modality , they knew the relationship of the nerve root , drg , lumbar spinal nerve root of foraminal and extraforaminal stenosis , and could detect the symptomatic lesions compared with the aymptomatic contralateral side .
this modality may fail to clearly reveal foraminal and extraforaminal anatomy in patients with spinal deformities , such as scoliosis or severe lordosis .
proset - mri was first suggested by borthne et al.1 ) to obtain excellent bowel image .
the principle of this modality is a selective excitation to suppress either fat or water by exploiting the difference between the water and fat resonance frequencies .
si of fat can be suppressed , and then si of water can be revealed . through this principle , we used the proset - mri to see the status of nerve root images at the lumbosacral space with three dimensional coronal ffe sequences .
if pain and/or radiculopathy are provocated and relieved during snrb , we confirmed as symptomatic stenosis . according to these symptomatic stenotic lesions
, we could know the definite findings of symptomatic lesion at three dimensional proset - mri that had root swelling and/or indentation .
in addition , when the pain and/or radiculopathy symptoms are relieved after decompressive surgery at foraminal and extraforaminal stenosis , we detected the same reliable three dimensional proset - mri findings .
when there are reliable symptomatic findings of proset - mri , we will predict good results after snrb or decompressive surgery .
however , we do not have long - term follow - up data that may show the degree of reducing nerve root swelling and/or root indentation .
although we obtained meaningful results of pain , we do not know the precise expectant radiological period to obtain good effects of treatments and indication of each treatment options .
we did not know the exact degree of rs and indentation to induce the symptoms .
the degree to induce the symptoms can provide us to detect the accurate period of treatment . in our study , we had one - month follow - up with proset - mri at decompressive surgery of only two patients .
these patients ' findings of proset - mri showed only a reduction in nerve root swelling , and not fully recovered indentation .
although there was remained indentation of nerve root , patients ' vas scores had good meaningful result with statistical significance .
we do not exactly know the asymptomatic cases with abnormal proset - mri findings because we just reviewed the abnormal radiologic changes combined with clinical symptoms .
therefore , we need further studies with many pretreatment cases of proset - mri and evaluate the status of posttreatment proset - mri .
we think that the three dimensional proset - mri can be a very useful and sensitive technique to diagnose the symptomatic foraminal and extraforaminal stenosis at l5-s1 .
therefore , we can see root swelling and indentation that are the most important radiological findings to match clinical symptoms more accurately by this proset - mri .
further studies and long - term follow - up will be necessary to verify the clinical usefulness of the three dimensional proset - mri in these patients .
 objectiveto suggest a new useful diagnostic technique , principles of the selective excitation technique - magnetic resonance images ( proset - mri ) , and to know the precise radiologic findings that can prove symptomatic foraminal and extraforaminal stenosis at l5-s1.methodsnineteen patients with symptomatic l5-s1 stenosis were checked by proset - mri . 
 four patients were performed decompressive surgery and 15 patients were performed selective nerve root block ( snrb ) at l5 . 
 the pain scale of patients was checked by visual analogue scale ( vas ) scores at the pre- and post - treatment state.resultsproset-mri findings of patients with symptomatic stenosis are root swelling ( rs ) and indentation . the comparisons with vas scores had a meaningful statistical result at each rs ( p<0.01 ) and indentation ( p<0.01 ) . 
 however , the findings of rs combined with indentation lacked statistical significance ( p=0.0249 ) . 
 in addition , according to a comparison with the treatment modalities , reducing of vas scores had statistical meaningful significance in decompressive surgery cases ( p<0.01 ) , and also in snrb cases ( p<0.01 ) after a 3-month follow - up period.conclusionthe three dimensional proset - mri is very useful and sensitive technique to diagnose the symptomatic foraminal and extraforaminal stenosis at l5-s1 . 
INTRODUCTION
MATERIALS AND METHODS
RESULTS
DISCUSSION
CONCLUSION