intraosseous arteriovenous malformation ( avm ) is a rare form of extracranial avm.5)6 ) the location most frequently involved is the craniofacial region , especially the mandible followed by the maxilla.2 ) most lesions present as excessive , recurrent hemorrhage following dental eruption or surgical extraction.2 ) we encountered a patient with klippel - trenaunay syndrome ( kts ) who presented with insidious onset of ipsilateral retroorbital pain , conjunctival injection , proptosis , and diplopia mimicking cavernous sinus dural arteriovenous fistula ( csdavf ) and was found to have an intraosseous avm involving the skull base . a 43-year - old female was referred to our hospital under the impression of a left csdavf . on presentation , she revealed left chemosis and proptosis that had developed ten days previously following several weeks of ipsilateral retroorbital pain and headache . brain magnetic resonance imaging ( mri ) from the referring hospital showed a dark - signaled void lesion at the left paracavernous region and mild dilatation of the ipsilateral cavernous sinus and superior ophthalmic vein . on physical examination , her right lower leg was hypertrophied with a geographic pattern of bluish cutaneous stains ( fig . no vascular bruit was audible in the limb and she had no complaints about her leg . we diagnosed our patient as kts basis on her features.8 ) angiography showed a triangular - shaped vascular chamber fed by multiple feeders of the left external carotid artery ( eca ) especially from the terminal branches of the left internal maxillary artery and accessory meningeal artery ( fig . the vascular chamber drained via the ipsilateral cavernous sinus with significant reflux into the ipsilateral superior and inferior ophthalmic veins while the inferior petrosal sinus was patent ( fig . a retrospective review of her brain mri showed that the vascular mass corresponded with the dark - signaled mass in the left side of the sphenoid body and the medial aspect of the greater wing ( fig . subsequent contrast - enhanced computed tomography ( ct ) revealed an osteolytic space of densely enhancing vascular chamber surrounded by a sclerotic bony margin , consistent with imaging findings of an intraosseous avm ( fig . we performed endovascular treatment with onyx ( ev3 , irvine , ca , usa ) embolization to relieve her orbital symptoms . vascular access was obtained with a 5f guiding catheter ( envoy , cordis , miami lakes , fl , usa ) . on the super - selective angiograms of the major feeders , we found that the feeders near the vascular chamber consisted of numerous fine arteries rather than sizeable fistulas . the left accessory meningeal artery was catheterized with a dimethysulfoxide ( dmso)-compatible microcatheter ( rebar 14 , ev3 , irvine , ca , usa ) , which was advanced to be sited in the prenidal position and successfully wedged . following successful solidification of the reflux , the liquid embolic material ( onyx 18 , ev3 , irvine , ca the post - embolization angiogram showed prominent reductions in vascularity and degree of av shunting . her eye symptoms gradually resolved over 3 days and she was discharged without any complications . intraosseous avm is very rare , with most reported lesions involving the head and neck region followed by the vertebra.2)5)6 ) thus , our patient was especially interesting , because of not only the rarity of intraosseous avm but the unusual clinical presentation with orbital symptoms . most craniofacial avms reported to date presented with dental bleeding or other hemorrhage following trauma.2 ) to our knowledge , there has been no report of intraosseous head and neck avm presenting with flow - related symptoms . similar to a benign csdavf , this patient may have remained asymptomatic if the major route of venous drainage continued to be via the inferior petrosal sinus ( ips ) . our patient became symptomatic due to retrograde reflux to the superior and inferior ophthalmic veins . angiographic diagnosis of intraosseous avm in the skull base was difficult because the nidus was located on the left side sphenoid body and adjacent greater wing , not far from the usual osseous type of skull base davf.4)7 ) in contrast to a typical osseous davf , our patient 's condition was characterized by a polygonal shaped venous chamber - not a network of fine vessels - within the bone as a large ectatic draining vein . we successfully reduced her orbital symptoms by reducing shunting flow after embolization of the venous chamber using onyx . considering our patient 's limb abnormality , the rare form of intraosseous avm in this patient may be related to kts . kts is characterized as a triad of a localized vascular nevus , congenital varicosities on the same body part , and hypertrophy of tissues on that body part . kts is frequently associated with congenital vascular malformations.8 ) however , vascular anomalies of the head and neck region are rarely associated with kts , and there have been no reports to date on this type of intraosseous avm in patients with kts.9 ) the associations between kts and vascular abnormalities in the head and neck region , including intraosseous avm , are not well understood . numerous protein factors have been found to regulate vascular morphogenesis.10 ) the kts susceptibility gene aggf1 was identified through genetic studies on vascular morphogenesis , but there is no clear evidence so far that kts is linked to any genetic aberration.1)10 ) intraosseous avm and kts may be pathogenically similar , in that both are caused by errors in vascular morphogenesis . future studies of genes involved in vascular anomalies may provide insights into their relationship . the kts patients are characterized as having , hypercoagulability , including higher rates of deep venous thrombosis ( dvt ) and thromboembolic complications than non - kts patients.3 ) aggressive intra- and postprocedural dvt prophylaxis has been recommended for these patients , and low - molecular - weight heparin may be effective.9 ) our patient was heparinized during the embolization procedure and administered low - molecular - weight heparin afterward . this report describes a very rare case of intraosseous avm in the sphenoid bone associated with kts . if an endovascular treatment is considered in kts patients , it is important to know specific characteristics of this syndrome , including hypercoagulability , reducing any periprocedural thrombosis related morbidity . we report an extremely rare case of intraosseous avm involving the sphenoid bone , associated with kts .
intraosseous arteriovenous malformation ( avm ) in the craniofacial region is rare . 
 when it occurs , it is predominantly located in the mandible and maxilla . 
 we encountered a 43-year - old woman with klippel - trenaunay syndrome affecting the right lower extremity who presented with a left orbital chemosis and proptosis mimicking the cavernous sinus dural arteriovenous fistula . computed tomography angiography revealed an intraosseous avm of the sphenoid bone . 
 the patient 's symptoms were completely relieved after embolization with onyx . 
 we report an extremely rare case of intraosseous avm involving the sphenoid bone , associated with klippel - trenaunay syndrome .