spinal dural ateriovenous fistula ( sdavf ) is the lesion within dural leaflets due to direct arterial - to - venous shunt .
dural ateriovenous fistula ( davf ) at the craniocervical junction is rare , as an uncommon type of sdavf , which has been documented in sevral case reports2,3,4,8 )
we report a patient who presented brainstem dysfunction due to davf at the craniocervical junction that was cured by transarterial onyx embolization .
it is a very rare case when symptoms are caused by abnomal venous drainage . on the other hand , onyx embolization for davf in this area
a 46-year - old female patient presented with a history of one month 's duration of vertigo , gait , nausea , vomiting and dysphagia , which developed progressively .
she was referred for a brain mri study with a preliminary diagnosis of brainstem infarction in a local hospital .
t2-weight mri and flair image showed high signal intensity swelling from pons to medulla oblongata ( fig .
low signal intensity and partial enhancement in the same territory were detected on t1-weight and contrast enhanced imagings ( fig .
neurologic examination revealed attenuation of left - side gag reflex and right - side nasolabial groove .
tongue extension moved to the right and muscular strength of left limbs was iv in this case .
spinal mri disclosed abnormal flow void at ventral surface from craniocervical junction to cervical cord , suggesting engorged vessels ( fig .
cerebral angiography performed five days after admission revealed davf with a meningeal branch originated from the radicular artery of the right c2 segment of va as a feeding vessel , draining via abnormally hypertrophic pontomesencephalic veins ascending into basal vein retrogradely and descending into the anterior spinal vein , anterior internal vertebral venous plexus and vertebral artery venous plexus ( fig .
arterial feeder originated from external carotid artery ( eca ) was not disclosed from bilateral eca angiography .
a diagnosis of davf at the craniocervical junction with venous congestion of brainstem was made .
the patient underwent a transarterial endovascular embolization with onyx-18 ( ev3 , irvine , ca , usa ) .
intravenous heparin was given before the guiding catheter was advanced to keep activated clotting time from 200 to 300 seconds .
a six - french envoy guiding catheter ( cordis endovascular , miami lakes , fl , usa ) and a marathon microcatheter ( ev3 , irvine , ca , usa ) were used .
onyx-18 was injected using real - time digital subtraction fluoroscopic mapping after the microcatheter lumen was flushed with 0.3 ml dimethyl sulfoxide ( dmso , ev3 , irvine , ca , usa ) .
the injection was terminated when the angiogram confirmed complete obliteration of the fistula ( fig .
low - molecular - weight heparin ( lmwh ) injection , aspirin and clopidogrel were administrated after endovascular treatment .
meanwhile , aspirin ( 100 mg ) and clopidogrel ( 75 mg ) , once a day , were administrated for one month .
this patient has been followed - up for six months and recovered completely without any neurological deficits .
cerebral angiography performed at six months after embolization showed complete obliteration of the fistula and disappearance of abnormal venous drainage ( fig .
sdavf is a common type of spinal vascular malformation in adult that usually affects the lumbar or lower thoracic spine .
review of the literature revealed that davfs occuring at the craniocervical junction had been called davfs at the foramen magnum and often present with progressive myelopathy or sah2,3,4,8 ) .
only one case in this anatomical area has been reported to involve brainstem dysfunction10 ) .
brainstem dysfunction as an initial symptom has been documented in several cases of ccfs or intracranial davfs1,6,9,12,15,17,18 ) .
congestion caused by venous hypertension was also considered as a probable pathological mechanism . in here we describe a case presenting with brainstem dysfunction at onset .
a cerebral angiogram confirmed a davf at the craniocervical junction that was supplied by the meningeal branch originated from the radicular artery of the right va with ascending and descending venous drainage .
davf ought to be considered for these dysfunctions to avoid catastrophic outcomes such as brainstem hemorrhage or necrosis which might result from erroneous diagnosis followed by incorrect therapy8,11,15 ) .
brainstem venous congetion may be caused by elevated venous pressure secondary to arterial pressure via fistula . in previously reported cases of sdavfs ,
three major anomalous venous drainage patterns were recognized : ascending , descending and undetected8,13 ) .
ascending venous drainage into intracranial sinus was considered to account for sah caused by venous hypertension .
moreover , a descending venous drainage was considered for myelopathy . ascending along with descending venous drainage
the previous two cases of cervical davfs and one of lumbar spinal davf that presented brainstem dysfunctions demonstrated a similar ascending venous drainage ( table 1)10,19,20 ) .
venous flow drains into the transverse sinus , the petrosal sinus and the straight sinus under normal physiological conditions14 ) . in a retrograde ascending venous drainage system of the cervical davf
if the venous flow increases precipitously , an elevated hemodynamic stress , varix formation or even hemorrhage may occur5,8 ) . however , this patient and the other three cases reported with ascending drainage presented braistem dysfunction rather than hemorrhage ( table 1 ) .
we found that retrograde flow in each case was slow and the draining volume was not very high . under this condition ,
normal brainstem venous drainage would be stagnant , resulting in congestion and edema , similarly to myelopathy caused by venous hypertension as it is seen in some cases of sdavfs7 ) .
therefore , the aim of treatment is to obliterate abnormal shunt and venous drainage as well as relieving venous congestion .
onyx , as a novel liquid embolic agent , has being an alternative option in the treatment of cerebral and spinal vascular malformations16 ) .
surgical approach would be difficult and at high risk when the fistula and draining veins are located at the ventral side of the foramen magnum .
this patient was treated with endovascular treatment using transarterial onyx embolization , which is safer and more controllable than former endovascular theraputic approaches .
onyx-18 was injected with a " hold - reinjection " technique to avoid glue migration to the proximal trunk of the feeding artery under real - time digital subtraction fluoroscopic mapping .
anticoagulant and antiplatelet therapy were performed to prevent thrombosis caused by blood flow stasis in the arterialized drainage vein due to closure of a fistula .
this patient recovered completely without any neurological deficits as determined during the follow - up period .
brainstem anomalous signals of t1-weight , t2-weight and contrast - enhanced t1-weight imaging had disapeared by the latest mri study , which verified the lesion congestion rather than infarction .
retrograde ascending venous drainage of the davf at the craniocervical junction , when venous flow is not high , may induce brainstem venous congestion
. congestion could be reversible if davf is considered as a differential diagnosis for brainstem dysfunction of undetermined origin and appropriate treatment was performed promptly to avoid poor outcomes .
moreover , onyx embolization is an alternative option for the treatment of davf at the craniocervical junction .
 dural ateriovenous fistula ( davf ) at the craniocervical junction is rare . 
 we report a patient presenting with brainstem dysfunction as an uncommon onset . 
 brainstem lesion was suggested by magnetic resonance image study . 
 angiogram revealed a davf at a high cervical segment supplied by the meningeal branch of the right vertebral artery , with ascending and descending venous drainage . 
 complete obliteration of the fistula was achieved via transarterial onyx embolization . 
 clinical cure was achieved in the follow - up period ; meanwhile , imaging abnormalities of this case disappeared . 
 accordingly , we hypothesize that a brainstem lesion of this case was caused by craniocervical davf , which induced venous hypertension . thus , venous drainage patterns should be paid attention to because they are important for diagnosis and theraputic strategy . 
INTRODUCTION
CASE REPORT
DISCUSSION
CONCLUSION