the spinal dural arteriovenous fistula ( sdavf ) is the most common type of spinal vascular malformation , but it is rare condition in overall incidence561013171820 ) .
it is characterized by progressive , insidious , and non - specific symptoms that are similar to those of more common etiology , such as degenerative spinal disorder and peripheral neuropathy5131920 ) .
the fistulas of sdavf are located intradurally at the sleeve of the nerve root , and the obliteration of fistulas is the treatment goal for sdavf513182223 ) .
sdavf can be treated by surgical interruption and endovascular embolization . to help ensure successful treatment ,
we present a patient with sdavf and a history of paraparesis during spinal angiography who was treated successfully using stereotactic radiosurgery ( srs ) using novalis system .
a 43-year - old man presented with slow progression of back pain , voiding difficulty , and boring pain on both lower extremities during 5 months .
neurological examination showed 420motor weakness of grade iv in both legs and his anal tone was grade zero .
about 14 years ago , he had pain in the left leg and was diagnosed with spinal arteriovenous malformation . at that time , magnetic resonance imaging ( mri ) of the thoracolumbar spine revealed a vascular anomaly at the thoracolumbar level , and physicians performed spinal angiography for definite treatment .
however , spinal angiography had failed three times in two other hospitals due to vasospasm and paraparesis .
he recovered from these symptoms spontaneously , and he had not undergone any treatment thereafter .
mri in our hospital showed a vascular anomaly with enhancement at the t12 , l1 , and l2 levels ( fig .
axial images of the l1 level revealed a mass lesion , located on the left side of the intraspinal canal ( fig .
we recommended selective spinal angiography , but the patient refused because of his experience , requesting a non - invasive technique for diagnosis and treatment .
however , we required an alternative modality to selective spinal angiography for obtaining accurate information on diagnosis , level of the lesion , and follow - up after treatment .
thus , a three - dimensional volumetric sagittal time - resolved imaging of contrast kinetics ( tricks ) abdominal magnetic resonance angiography ( mra ) using 1.5 t mri system were performed in quiet respiration ( tr / te / flip=4.2/1.1/45 , fov 330330 , equivalent slice thickness of 3 mm , matrix 256160 ) . contrast medium ( 15 ml gadolinium )
the study was post - processed into maximum - intensity projection ( mip ) images ( fig .
the target , involving the dura margin , was constructed to include the fistula during structural segmentation under spinal computed tomography ( ct ) images ( fig .
we used 10 conformal beams and a total irradiation of 18 gy with three fractions ( fig .
we checked the three - dimensional sagittal tricks abdominal mra using 1.5 t for follow - up 7 months after srs , and three - dimensional sagittal tricks abdominal mra using 3.0 t mri system ( tr / te / flip=10.0/1.5/30 , fov 380380 , equivalent slice thickness of 4 mm , matrix 384160 ) was performed 3 years after radiosurgery .
the size of the spinal lesion was decreased and the flow through the fistula was diminished on the 7-month post - treatment images ( fig .
4a ) , and the sequelae of the previous lesion was presented on follow - up mri and mra images ( fig .
sdavf represent a rare pathological condition , but they account for 6080% of all spinal vascular malformation61317182023 ) .
they are acquired lesions , and usually present with insidious and progressive symptoms , such as paraparesis and sensory deficits of the bladder , bowel , and lower extremities10131718 ) . as they present with non - specific and misleading clinical symptoms ,
their most common site is the thoracolumbar region , and the arteriovenous shunt is a low - flow shunt located at the dural sleeve of the spinal nerve root56101323 ) .
the pathophysiology of sdavf - induced spinal cord ischemia and myelopathy is due to increased venous pressure , venous congestion , and decreased spinal cord perfusion caused by shunting arterial blood into the venous side56121315171823 ) .
treatment methods for these lesions are microsurgery and endovascular embolization . because the selection of treatment method is mediated by the physician 's preference ,
selective spinal angiography is regarded as an essential procedure to confirm and treat sdavf5 ) . for successful surgery or endovascular coiling ,
selective spinal angiography is necessary to know the architectures and hemodynamics of the lesion561215181922 ) .
however , even with experienced neuro - interventionists , selective spinal angiography can sometimes cause complications from vasospasm , increased venous pressure , and spinal cord infarction6812151720 ) . in our case , the patient experienced paraparesis three times during spinal angiography .
although it occurred 14 years previously , the patient refused the spinal angiography . because the patient wanted a noninvasive method for diagnosis and treatment , we found an imaging technique to provide information about the lesion and be available for follow - up .
there are some advanced imaging techniques for sdavf , such as contrast enhanced magnetic resonance angiography with high resolution , tricks sequence , gradient echo , and spinal angiography with a 256-slice ct23152024 ) .
although the role of advanced imaging techniques is limited to reducing the exposure of contrast and radiation during the subsequent selective spinal angiography61215202124 ) , it is sufficient for diagnosing sdavf and localizing the fistula235152024 ) . of these imaging techniques
, we used the three - dimensional sagittal tricks abdominal mra to obtain information about the spinal lesion and plan the srs .
srs for sdavf is not an established method , so reports regarding sdavf treated by srs are very rare .
however , in terms of radiosurgery for cranial dural arteriovenous fistulas , radiosurgery for sdavf is not an impossible treatment option22 ) .
gao et al.7 ) reported that high expression state of endothelial progenitor cells ( epcs ) presented in the brain and spinal arteriovenous malformation ( avm ) tissue .
other authors have published the results from an experimental study that radiosurgery decreases angiogenic activity in avm tissue , compared to that in untreated avm tissue1 ) . moreover , in an experimental study by jahan et al.9 ) , srs for an artificial animal avm model showed a reduction in the size of the lesion , compared to that in the non - radiosurgical model .
although these studies are not results for sdavf , we thought that it was possible to perform radiosurgery for sdavf .
dalyai et al.4 ) reported that srs for arteriovenous fistula lesions did not clearly show the mechanisms of treatment results , but they induced smooth muscle expansion , adventitial fibrosis , and an intimal response of arterial feeders , and eventually achieved obliteration of the fistula .
however , it is not easy to find the exact location of fistulas with ct and mri - based image - guided structural segmentation .
thus , we planned the target area to include the dura margin , because fistulas of sdavf are located at the sleeve of the nerve root in the intradural space5131822 ) .
the planning of the radiosurgical dose was based some study , which the appearance of myelopathy from srs to spinal lesions appear rare ( < 1% ) when the maximum spinal cord dose is limited to the equivalent of 13 gy in a single fraction or 20 gy in three fractions1114 )
. however , these studies did not provide sufficient long - term data , and our patient had preexisting myelopathy .
thus , we treated him with a slightly lower dose than those in the references .
advanced imaging studies , including the three - dimensional sagittal tricks sequence , may be useful for obtaining information about sdavf and in performing srs and follow - up after srs when selective spinal angiography has failed .
and we think that srs may be another treatment option , especially , for patients preferring non - invasive procedures .
our study has the obvious limitation of only including one treatment case , so additional cases of sdavf treated by srs are necessary to determine if it is an effective treatment for this condition .
 the spinal dural arteriovenous fistula ( sdavf ) is rare , presenting with progressive , insidious symptoms , and inducing spinal cord ischemia and myelopathy , resulting in severe neurological deficits . 
 if physicians have accurate and enough information about vascular anatomy and hemodynamics , they achieve the good results though the surgery or endovascular embolization . 
 however , when selective spinal angiography is unsuccessful due to neurological deficits , surgery and endovascular embolization might be failed because of inadequate information . 
 we describe a patient with a history of vasospasm during spinal angiography , who was successfully treated by spinal stereotactic radiosurgery using novalis system . 