The Neuroradiology Journal 21: 433-439, 2008
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High-flow Paraspinal Osseous Epidural Arteriovenous Fistula A Case Report YUO IIZUKA, MITIMASA SUZUKI, KAZUHIRO SUZUKI, KEIGO SHIMOJI, SHINJI KOMURA Division of Neuroradiology, Department of Radiology, Juntendo Hospital, Juntendo University, School of Medicine. Tokyo, Japan
Key words: spinal osseous arteriovenous fistula, paravertebral arteriovenous fistula, transarterial embolization Abbreviations: SOEAVFs = spinal osseous epidural arteriovenous fistulas; AVMs = arteriovenous malformations; AVFs = arteriovenous fistulas; MR = magnetic resonance; CT = computed tomography
SUMMARY – We report the clinical and neuroradiological imaging findings of a 26-year-old man who presented with lumbago related to high flow paraspinal osseous epidural arteriovenous fistulas in the thoracic spine. This case was of particular interest because of his exclusive epidural and paraspinal venous drainage and the presence of a prominent dilated venous pouch in the spinal canal. Angiography demonstrated multiple high flow arteriovenous fistulas with an osseous nidus. Transarterial glue embolization was performed by multistage sessions. Clinical symptoms improved dramatically. The unusual features of this case have important implications for therapeutic management.
Introduction Spinal arteriovenous communication occurring outside the dura may be called paravertebral, paraspinal or epidural arteriovenous fistulas or malformations 1-4. Among spinal vascular lesions, these lesions are encountered infrequently. Spinal osseous epidural arteriovenous fistulas (SOEAVFs), first discriminated by Suh, are an extremely rare entity that is not well known 5. We present a unique clinical case of spinal epidural AVFs with a dilated venous pouch inside the spinal canal, which may be similar to the SOEAVFs reported by Suh. This study reviewed the clinical spectrum, neuroradiological imaging features and therapeutic indications for SOEAVFs. Case Report A 26-year-old man had a six month history of intractable lumbago. Weakness of the bilateral lower extremities progressed gradually until he could no longer walk unassisted. There was
no history of trauma. He was admitted to the department of orthopedics at the local hospital, and referred to a general hospital. Although surgical intervention was attempted by orthopedists under suspicion of vertebral hemangioma, control of hemostasis was difficult, and the surgeon finally abandoned the procedure. The patient was transferred to our institute for further examination and treatment. On admission, neurological examination was positive for pathological reflexes (Babinski & Chaddock), and progressive radiculopathy, sensory disturbance, rectourinary bladder dysfunction. Manual muscle test (MMT) of the bilateral lower extremities was 2/5. Slight cardiomegaly (cardio-thoracic ratio: 73%) was present. Magnetic resonance (MR) T2WI showed dilated vascular flow void structures with syringomyelia (figure 1A). Axial MRI showed that the vascular dilatations occupied the deformed thoracic vertebral body and spinal canal space at the left eleventh intervertebral foramen (figure 1B). There was a bony defect on the left side of the eleventh thoracic spinal vertebral body and enlargement of the left eleventh vertebral 433
High-flow Paraspinal Osseous Epidural Arteriovenous Fistula
Yuo Iizuka
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B
C
D
E
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foramen with a loss of cortical margin by contrast enhanced computed tomography (figure 1C). Selective spinal angiography disclosed the epidural arteriovenous fistulas fed by the bony and dural branches of the left eleventh intercostal segmental arteries. Rapid multiple arteriovenous shunts were located at the epidural intravertebral canal. A dilated venous pouch recruited multiple arterial feeders unlike other draining veins. The draining pathway connected to the paravertebral Batson’s venous plexus, inferior vena cava and azygos vein (figure 1D). The associated osseous feeders from the intercostal arteries arose from the upper or lower segments of the ipsilateral and contralateral arteries (figure 1E,F,G). The therapeutic management was fully discussed with the orthopedist. Surgical intervention had already been attempted at the previous institute, but 434
resulted in technical failure. The possibility of endovascular intervention was discussed. By an arterial approach, the spinal feeding artery, such as the radiculomedullary or radiculopial artery might be masked around TH 11 level, because of the high flow arteriovenous fistula. By a venous approach, there were two concerns that caused hesitation. The first was the inability to differentiate the intraosseous venous pouch and intracanalicular dilated venous pouch. The second was the mass effect of the dilated venous pouch could be considered one of the etiological factors contributing to symptoms in this patient. Although transvenous coil embolization might have been possible, elaborate catheterization of the feeding arteries, and highly concentrated glue embolization via the transarterial approach was selected as a therapeutic strategy. The first endovascular
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The Neuroradiology Journal 21: 433-439, 2008
H
Figure 1 A) Sagittal T2-weighted MR image shows dilated venous pouch at Th11 spinal canal. Syringomyelia presented in the thoracic spinal cord. B) Axial T1-weighted MR image reveals vascular flow void low signal intensity within the bony defect and peripheral dilated venous plexus of the 11th thoracic spine. Spinal cord is compressed and shifted to the right dorsal area. C) Contrast enhanced computed tomography at 11th thoracic spine shows erosive defect of spine and pedicle with dilated epidural and paravertebral venous plexus. D) Left 11th intercostal arteriography in oblique view discloses multiple fistulas and bony nidus draining into the dilated epidural venous pouch. Venous engorgement and venous drainage through the hemi-azygos vein into the opening site of the azygos vein to the superior vena cava detect in same phase. E) Right 11th intercostal arteriography presents associated multiple fistulae and nidus to the contralateral side venous pouch. The same dilated venous system proves to be a draining pathway. F) Left 12th intercostal arteriography showing faint associated feeders to the venous pouch at Th11. G) Right 12th intercostal arteriography showing associated feeders conversing to the thoracic 11th vertebral body and venous pouch. H) Left 10th intercostal arteriography feeding associate bony nidus with ASA.
intervention was attempted under intubated general anesthesia. Transarterial glue embolization of three main high flow AVFs at the left eleventh intercostal artery was performed with pure N-butyl-cyanoacrylate mixed with tantal powder. After the intervention, MMT improved from 2/5 to 3/5, and pathological reflexes (Babinski & Chaddock) disappeared. Although the patient could not move himself on the bed without assistance before the first interventional procedure, he could change positions on the bed by himself, and sit alone after the intervention. Despite marked improvement of neurological findings, MRI and CT did not demonstrate morphological improvement in the dilated venous pouch. After three months, the second endovascular intervention was performed to close the residual shunts from the four feeding vessels by the eleventh intercos-
tal arteries. Abnormal AVFs were closed with glue. He could finally walk alone after rehabilitation training. Another two months later, the third endovascular intervention was performed to close the peripheral residual shunts. Abnormal AVFs from five feeding vessels were closed with diluted glue. During the third intervention, the anterior spinal artery was detected at the left tenth intercostal artery (figure 1H). By diagnostic spinal angiography, this anterior spinal axis was not opacified because of high flow through the fistula, or masked by associated osseous nidus around the main arteriovenous fistula (not shown). A further two months later, the fourth endovascular intervention was performed to close residual shunts. From the seven feeding arteries, abnormal AVFs were closed with diluted glue. (figure 2) The final control angiogram 435
High-flow Paraspinal Osseous Epidural Arteriovenous Fistula
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B
Figure 2 Three dimensional reconstruction computed tomography demonstrating high density embolized glue deposition around the venous pouch.
Figure 3 A,B MR sagittal T1 weighted (A) and T2 weighted (B) images confirming the thrombosis of the venous pouch 5 years after intervention.
demonstrated markedly reduced shunt flow, although there was a faint residual shunt. A total of 19 feeding arteries were catheterized during four sessions, which closed about 75% of the abnormal arteriovenous fistula with transosseous AVM components around TH 11. There was no complication related to the therapeutic procedure. Findings on neurological examination were normal and there has not been any recurrence of symptoms during the six year follow-up period. Follow-up MRI demonstrated thrombosis inside the dilated venous pouch (figure 3A, B).
vertebral fistulas or nonvertebral segmental nerve fistulas 6, vertebral bone AVFs 8, slowflow epidural AVFs with intradural reflux 8-9, and other extradural AVFs 10-11. An associated group included metameric lesions and systemic disease such as Elheros-Danlos-IV, fibromuscular dysplasia (table 1). Emery et Al reported 14 pediatric spinal arteriovenous malformations. Among these, there were three epidural cases. A seven-month-old girl associated with Cobb’s syndrome demonstrated high flow epidural AVFs that presented as flank mass. A one-year-old boy associated with teratoma at conus medullaris also demonstrated high flow AVF that presented with neurological deficit. Asymptomatic thoracic spinal vertebral bone AVMs supplied intersegmental arteries. Venous drainage was toward the epidural non-dilated veins as well as toward the azygos and hemi-azygos route. Although three of these cases were included among individually different extradural (epidural/paraspinal) AVFs/AVMs entities, these lesions may all be included in the isolated group 8. In the present case, the lesion is located in the epidural space involving a bone at the site of the dilated venous pouch to which all the feeders are conversing. The flow to the venous pouch itself is rapid like that seen in traumatic
Discussion Classification
Spinal arteriovenous communication can be classified into spinal cord AVMs and AVFs, spinal dural AVFs, and extradural AVMs and AVFs according to the anatomic space 1-3. Among these lesions, the paravertebral groups are recognized as very rare entities. Paravertebral spinal vascular lesions are subcategorized into two main groups, isolated and associated. The isolated group is discriminated by paraspinal AVFs along the segmental nerve 4: vertebral436
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Table 1 Classification of Spinal AVMs/AVFs
Epidural/Paraspinal AVFs/AVMs #Isolated 1. paraspinal AVFs along the segmental nerve a. vertebrovertebral fistulas b. non vertebral segmental nerve fistulas 2. vertebral bone AVMs 3. slow-flow epidural AVFs w/ intradural reflux 4. other extradural AVFs / AVMs #Associated 1. metameric 2. systemic dysplasia Dural AVFs Intradural AVFs/AVMs #Isolated #Associated
or neurofibromatosis type I lesions. Shunt flow to the osseous component seemed to be relatively slower than that of the main shunts from the peripheral intercostal artery. The osseous vertebral nidus was presumed to be the result of a secondary sump phenomenon produced by the rapid flow in the main AVFs. Therefore, the present case showed a different flow pattern from the two cases of SOEAVFs reported by Suh, which were both slow flow shunts. The reason for the discrepancy of shunt speed between our case and that reported by Suh is unclear 5. An initial stage and advanced stage in the same region may be one of the possible explanations. The present case is considered the combined type of extradural AVF and associated secondary bone AVM. Symptoms
The etiology of paravertebral AVMs is reported to be congenital, spontaneous, traumatic, iatrogenic or systemic syndrome causing dysplastic vessels such as neurofibromatosis type I 11 , Elheros-Danlos-IV, fibromuscular dysplasia. Paravertebral spinal AVMs have been detected
The Neuroradiology Journal 21: 433-439, 2008
incidentally or by presentation with compressive myelopathy or venous congestive myelopathy. These lesions can also present with a subcutaneous pulsating mass in the paravertebral musculature, spinal canal deformity, cardiac failure or bleeding. In our case, the clinical manifestations were assumed to have resulted from three etiological factors: direct mechanical compression by dilated venous vessels, long-term venous hypertension and vascular steal phenomenon. Symptoms in SOEAVFs may start as radiculopathy, presenting as lumbago as shown in our case. A fistulous dilated vein can lead to radicular pain from mechanical compression of the spinal cord, spinal nerve root. It can contribute to the maldevelopment of the neighboring spine causing a bone defect. Numerous osseous and epidural branches of the intersegmental arteries as well as anastomosis with upper or lower segments or contralateral arteries explain why multiple arteries frequently feed these fistulas, located in the epidural space. Regurgitation into the perimedullary vein from paravertebral/epidural shunts frequently confirm symptomatic cases. In case of disturbance or steno-occlusion at the venous outlet, intradural regurgitation can also lead to spinal congestive circulation and syringomyelia as seen in our patient. Previous case series reported these morphological findings and already established the clinical mechanisms 12-21. The venous return of the main radiculomedullary circulation was not visible, perhaps because it was diluted by the venous return of the fistula or congestive venous hypertension similar to that in spinal dural AVFs. From an anatomical and embryonic perspective, paraspinal epidural AVFs and the cavernous sinus dural AVFs could be linked, since these are both osteodural in location. When looking at the difference in the venous structures of spinal and intracranial lesions, the absence of a dural venous sinus in the spinal region is obvious. Venous sinuses like vascular pathways within the dural sheath can hardly be considered the same entity as venous channels located within the epidural space. There are no venous dural sinuses at the sphenoid level and the spinal epidural venous plexus has the same appearance all along the notochord from the sacrum to the skull-base 1. Paraspinal Batson’s venous system is a valveless draining pathway. The epidural venous channels have rich axial and longitudinal anastomoses. Elevation of Batson’s venous pressure automatically interferes with 437
High-flow Paraspinal Osseous Epidural Arteriovenous Fistula
the spinal venous drainage, even though there is a systemic diffusion phenomenon as a result of elevated venous pressure. These hemodynamic changes may ultimately lead to right cardiac overload. Myelopathy in the present case seemed to be a late manifestation caused by longstanding venous hypertension of the epidural plexus without intradural reflux. Congestion of the medullary vein even without any retrograde drainage could explain the inability to visualize the medullary drainage, and account for the clinical symptoms. The main site of interference with cord function due to high-pressure blood flow in the coronal venous plexus was in the region of the spine where the fistula was located. Although the mechanisms underlying syringomyelia in paravertebral vascular malformation are not well understood, direct mechanical compression of the spinal cord or CSF pressure gradient change may be involved. The clinical significance of arterial steal was difficult to explain, but it might have been responsible for spinal cord symptoms, especially when the spinal medullary artery branched at the same level as the main shunts similar to that in the present case. Intervention
During the attempt at surgical resection of the present SOEAVF at the previous institute, the surgeon had considerable difficulty in controlling hemorrhage from the osseous AVMs component. We consider that endovascular embolization is the treatment of choice for SOEAVFs. Regarding arterial access, this case presented some suspected risk factors. The prominent flow into the shunts may preclude appropriate opacification of a radiculomedullary artery originating at the same level. Actually, the spinal medullary artery originated from Th10 in the present case. Although it was not recognized on earlier diagnostic images, the artery became apparent among the osseous vascular components during the third intervention. Embolization of the anterior spinal axis through the radiculomedullary branches originating at the same segmental level as the fistula must be avoided. Elaborate superselective catheterization to the feeding arteries and careful staged planning are indispensable to avoid catastrophic complications. Regarding the venous approach, the first problem was the vascular anatomy of the lesion itself. It might be difficult to visualize the exact drain-
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ing site on conventional angiography because of the rapid speed and high volume shunt flow through the fistula and overlapping venous structures. Occlusion of the draining vein without shunt closure might present a high risk of hemorrhage. In two similar cases of SOEAVF reported by Suh et Al, they described the fistula site as a round fistular nidus, which was the target of the transvenous coil embolization. For venous occlusion, coils can be used, giving the theoretical advantage of progressive occlusion. Technical difficulty in placing coils only in the dilated venous pouch was also suspected because of the irregular shape of the venous angioarchitecture in our diagnostic images. The second problem was more complex. Considering the risk of mass effect from the dilated vein compressing the spinal cord, we were concerned about that transvenous coil embolization would not improve the symptoms. These unusual features have important implications for treatment. In our opinion and based on our experience, although a single hole fistula is best treated using a detachable balloon, liquid embolic material, such as NBCA, is the most appropriate material for arterial embolization of complex spinal AVFs. As a permanent embolic agent, NBCA offers immediate and durable occlusion for high flow AVFs. Several technical adjuncts helped to control the flow during injection of the liquid embolic agent, simplifying the obliteration of the fistulas without migration of the embolization material into the venous system. Controlled hypotension during pure glue injection is routinely used in our institute. We also make a continuous pure NBCA column by continuously pushing very slowly using a 2.5cc syringe. Conclusion A patient with complex SOEAVF was presented. Transarterial glue embolization by multiple staged sessions achieved a good clinical and morphological outcome in our case. Endovascular glue intervention is a safe and effective treatment modality for this condition and should be the first choice of treatment. High-flow SOEAVF may be curable by carefully planned and staged intervention. In the present case, congestive myelopathy produced by elevation of Batson’s venous system was considered the main etiological factor.
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The Neuroradiology Journal 21: 433-439, 2008
References 1 Lasjaunias P, Berenstein A, Ter brugge KG: 11 Spinal Arteriovenous malformations. Vol:2 Clinical and Interventional Aspect in Adult. Surgical Neuroangiography. Second edition. Berlin: Springer-Verlag 2001: 738-849. 2 Lasjaunias P: 11 Spinal Arteriovenous Shunts. Vascular Diseases in Neonates, Infants and Children: Interventional Neuroradiology Management. Berlin: Springer 1997: 531-563. 3 Bao YH, Ling F: Classification and therapeutic modalities of spinal vascular malformations in 80 patients. Neurosurgery 40: 75-81 1997. 4 Niimi Y, Berenstein A, Fernandez PM et Al: Pediatric nonvertebral paraspinal arteriovenous fistulas along the segmental nerve:clinical, imaging, and therapeutic considerations. J Neurosurg 103: 156-162, 2005. 5 Shu DC, Choi CG, Sung KB et Al: Spinal Osseous Epidural Arteriovenous Fistula with Multiple Small Arterial Feeders Conversing to a Round Fistular Nidus as a Target of Venous Approach. Am J Neuroradiology 25: 69-73, 2004. 6 Hui F, Trosselo MP, Meisel HJ et Al: Paraspinal arteriovenous shunts in children. Neuroradiology 36: 6973, 1994. 7 Emery DJ, Willinsky RA, Burrow PE et Al: Paediatric Spinal Arteriovenous Malformations: Angioarchitecture and Endovascular Treatment. Interventional Neuroradiology 4: 127-139, 1998. 8 Silva n, Janel AC, Tall P et Al: Spinal epidural arteriovenous fistulas associated with progressive myelopathy. Report of four cases. J Neurosurg Spine 6: 552-8, 2007. 9 Chaung NA, Shroff MM, Willinsky RA et Al: Slow-Flow Spinal Epidural AVF with Venous Ectasias: Two Pediatric Case Reports. Am J Neuroradiol 24: 1901-1905, 2003. 10 Chen CJ, Huang CC, Hsu YY et Al: Small Isolated ParaspinalArteriovenous Fistula. Am J Neuroradiology 18: 359-361, 1997. 11 Cognard C, Sernaan H, Bakchine S et Al: Paraspinal arteriovenous fistula with perimedullary venous drainage. Am J Neuroradiol 16: 2044-2048, 1995. 12 Matsumura A, Tsuboi K, Hyodo A et Al: Lumbosacral extradural spinal arteriovenous malformation with blood supply from branches of internal iliac arteries. Neurochirurgia 29: 235-237, 1986. 13 Han SS, Love MB, Simeone FA: Diagnosis and treatment of a lumbar extradural arteriovenous malformation. Am J Neuroradiol 8: 1129-1130, 1987. 14 Szajner M, Weil A, Piotin M et Al: Endovascular Treatment of a Cervical Paraspinal Arteriovenous Malformation via Arterial and Venous Approaches. Am J Neuroradiol 20: 1097-1099, 1999. 15 Goyala M, Willinsky R, Montanera W et Al: Paravertebral Arteriovenous Malformations with Epidural Drainage: Clinical Spectrum, Imaging Features, and Results of Treatment. Am J Neuroradiol 20: 749-755, 1999. 16 Bradac GB, Simon RS, Schramm J: Cervical epidural AVM: report of a case of uncommon location. Neuroradiology 14: 97-100, 1977. 17 Asai J, Hayashi T, Fujimoto T et Al: Exclusively epidural arteriovenous fistula in the cervical spine with spinal cord symptoms: case report. Neurosurgery 48: 1372-5, 2001. 18 Pirouzmand F, Wallace C, Willinsky R: Spinal epidural arteriovenous fistula with intramedullary reflux. J Neurosurg 87: 633-635, 1997. 19 Willinsky R, terBrugge K, Montanera W et Al: Spinal
epidural arteriovenous fistulas: arterial and venous approaches to embolization. Am J Neuroradiol 14: 812817, 1993. 20 Arnaud O, Bille F, Pouget J et Al: Epidural arteriovenous fistula with perimedullary venous drainage: case report. Neuroradiology 36: 490-491, 1994.
Yuo Iizuka, MD Department of Radiology Juntendo Urayasu Hospital Juntendo University, School of Medicine 2-1-1, Tomioka Urayasu pref. 279-0021 Chiba, Japan Tel.: 047-353-3111 Fax: 045-353-3138 E-mail: [email protected]
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High-flow Paraspinal Osseous Epidural Arteriovenous Fistula A Case Report YUO IIZUKA, MITIMASA SUZUKI, KAZUHIRO SUZUKI, KEIGO SHIMOJI, SHINJI KOMURA Division of Neuroradiology, Department of Radiology, Juntendo Hospital, Juntendo University, School of Medicine. Tokyo, Japan
Key words: spinal osseous arteriovenous fistula, paravertebral arteriovenous fistula, transarterial embolization Abbreviations: SOEAVFs = spinal osseous epidural arteriovenous fistulas; AVMs = arteriovenous malformations; AVFs = arteriovenous fistulas; MR = magnetic resonance; CT = computed tomography
SUMMARY – We report the clinical and neuroradiological imaging findings of a 26-year-old man who presented with lumbago related to high flow paraspinal osseous epidural arteriovenous fistulas in the thoracic spine. This case was of particular interest because of his exclusive epidural and paraspinal venous drainage and the presence of a prominent dilated venous pouch in the spinal canal. Angiography demonstrated multiple high flow arteriovenous fistulas with an osseous nidus. Transarterial glue embolization was performed by multistage sessions. Clinical symptoms improved dramatically. The unusual features of this case have important implications for therapeutic management.
Introduction Spinal arteriovenous communication occurring outside the dura may be called paravertebral, paraspinal or epidural arteriovenous fistulas or malformations 1-4. Among spinal vascular lesions, these lesions are encountered infrequently. Spinal osseous epidural arteriovenous fistulas (SOEAVFs), first discriminated by Suh, are an extremely rare entity that is not well known 5. We present a unique clinical case of spinal epidural AVFs with a dilated venous pouch inside the spinal canal, which may be similar to the SOEAVFs reported by Suh. This study reviewed the clinical spectrum, neuroradiological imaging features and therapeutic indications for SOEAVFs. Case Report A 26-year-old man had a six month history of intractable lumbago. Weakness of the bilateral lower extremities progressed gradually until he could no longer walk unassisted. There was
no history of trauma. He was admitted to the department of orthopedics at the local hospital, and referred to a general hospital. Although surgical intervention was attempted by orthopedists under suspicion of vertebral hemangioma, control of hemostasis was difficult, and the surgeon finally abandoned the procedure. The patient was transferred to our institute for further examination and treatment. On admission, neurological examination was positive for pathological reflexes (Babinski & Chaddock), and progressive radiculopathy, sensory disturbance, rectourinary bladder dysfunction. Manual muscle test (MMT) of the bilateral lower extremities was 2/5. Slight cardiomegaly (cardio-thoracic ratio: 73%) was present. Magnetic resonance (MR) T2WI showed dilated vascular flow void structures with syringomyelia (figure 1A). Axial MRI showed that the vascular dilatations occupied the deformed thoracic vertebral body and spinal canal space at the left eleventh intervertebral foramen (figure 1B). There was a bony defect on the left side of the eleventh thoracic spinal vertebral body and enlargement of the left eleventh vertebral 433
High-flow Paraspinal Osseous Epidural Arteriovenous Fistula
Yuo Iizuka
A
B
C
D
E
F
foramen with a loss of cortical margin by contrast enhanced computed tomography (figure 1C). Selective spinal angiography disclosed the epidural arteriovenous fistulas fed by the bony and dural branches of the left eleventh intercostal segmental arteries. Rapid multiple arteriovenous shunts were located at the epidural intravertebral canal. A dilated venous pouch recruited multiple arterial feeders unlike other draining veins. The draining pathway connected to the paravertebral Batson’s venous plexus, inferior vena cava and azygos vein (figure 1D). The associated osseous feeders from the intercostal arteries arose from the upper or lower segments of the ipsilateral and contralateral arteries (figure 1E,F,G). The therapeutic management was fully discussed with the orthopedist. Surgical intervention had already been attempted at the previous institute, but 434
resulted in technical failure. The possibility of endovascular intervention was discussed. By an arterial approach, the spinal feeding artery, such as the radiculomedullary or radiculopial artery might be masked around TH 11 level, because of the high flow arteriovenous fistula. By a venous approach, there were two concerns that caused hesitation. The first was the inability to differentiate the intraosseous venous pouch and intracanalicular dilated venous pouch. The second was the mass effect of the dilated venous pouch could be considered one of the etiological factors contributing to symptoms in this patient. Although transvenous coil embolization might have been possible, elaborate catheterization of the feeding arteries, and highly concentrated glue embolization via the transarterial approach was selected as a therapeutic strategy. The first endovascular
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The Neuroradiology Journal 21: 433-439, 2008
H
Figure 1 A) Sagittal T2-weighted MR image shows dilated venous pouch at Th11 spinal canal. Syringomyelia presented in the thoracic spinal cord. B) Axial T1-weighted MR image reveals vascular flow void low signal intensity within the bony defect and peripheral dilated venous plexus of the 11th thoracic spine. Spinal cord is compressed and shifted to the right dorsal area. C) Contrast enhanced computed tomography at 11th thoracic spine shows erosive defect of spine and pedicle with dilated epidural and paravertebral venous plexus. D) Left 11th intercostal arteriography in oblique view discloses multiple fistulas and bony nidus draining into the dilated epidural venous pouch. Venous engorgement and venous drainage through the hemi-azygos vein into the opening site of the azygos vein to the superior vena cava detect in same phase. E) Right 11th intercostal arteriography presents associated multiple fistulae and nidus to the contralateral side venous pouch. The same dilated venous system proves to be a draining pathway. F) Left 12th intercostal arteriography showing faint associated feeders to the venous pouch at Th11. G) Right 12th intercostal arteriography showing associated feeders conversing to the thoracic 11th vertebral body and venous pouch. H) Left 10th intercostal arteriography feeding associate bony nidus with ASA.
intervention was attempted under intubated general anesthesia. Transarterial glue embolization of three main high flow AVFs at the left eleventh intercostal artery was performed with pure N-butyl-cyanoacrylate mixed with tantal powder. After the intervention, MMT improved from 2/5 to 3/5, and pathological reflexes (Babinski & Chaddock) disappeared. Although the patient could not move himself on the bed without assistance before the first interventional procedure, he could change positions on the bed by himself, and sit alone after the intervention. Despite marked improvement of neurological findings, MRI and CT did not demonstrate morphological improvement in the dilated venous pouch. After three months, the second endovascular intervention was performed to close the residual shunts from the four feeding vessels by the eleventh intercos-
tal arteries. Abnormal AVFs were closed with glue. He could finally walk alone after rehabilitation training. Another two months later, the third endovascular intervention was performed to close the peripheral residual shunts. Abnormal AVFs from five feeding vessels were closed with diluted glue. During the third intervention, the anterior spinal artery was detected at the left tenth intercostal artery (figure 1H). By diagnostic spinal angiography, this anterior spinal axis was not opacified because of high flow through the fistula, or masked by associated osseous nidus around the main arteriovenous fistula (not shown). A further two months later, the fourth endovascular intervention was performed to close residual shunts. From the seven feeding arteries, abnormal AVFs were closed with diluted glue. (figure 2) The final control angiogram 435
High-flow Paraspinal Osseous Epidural Arteriovenous Fistula
Yuo Iizuka
A
B
Figure 2 Three dimensional reconstruction computed tomography demonstrating high density embolized glue deposition around the venous pouch.
Figure 3 A,B MR sagittal T1 weighted (A) and T2 weighted (B) images confirming the thrombosis of the venous pouch 5 years after intervention.
demonstrated markedly reduced shunt flow, although there was a faint residual shunt. A total of 19 feeding arteries were catheterized during four sessions, which closed about 75% of the abnormal arteriovenous fistula with transosseous AVM components around TH 11. There was no complication related to the therapeutic procedure. Findings on neurological examination were normal and there has not been any recurrence of symptoms during the six year follow-up period. Follow-up MRI demonstrated thrombosis inside the dilated venous pouch (figure 3A, B).
vertebral fistulas or nonvertebral segmental nerve fistulas 6, vertebral bone AVFs 8, slowflow epidural AVFs with intradural reflux 8-9, and other extradural AVFs 10-11. An associated group included metameric lesions and systemic disease such as Elheros-Danlos-IV, fibromuscular dysplasia (table 1). Emery et Al reported 14 pediatric spinal arteriovenous malformations. Among these, there were three epidural cases. A seven-month-old girl associated with Cobb’s syndrome demonstrated high flow epidural AVFs that presented as flank mass. A one-year-old boy associated with teratoma at conus medullaris also demonstrated high flow AVF that presented with neurological deficit. Asymptomatic thoracic spinal vertebral bone AVMs supplied intersegmental arteries. Venous drainage was toward the epidural non-dilated veins as well as toward the azygos and hemi-azygos route. Although three of these cases were included among individually different extradural (epidural/paraspinal) AVFs/AVMs entities, these lesions may all be included in the isolated group 8. In the present case, the lesion is located in the epidural space involving a bone at the site of the dilated venous pouch to which all the feeders are conversing. The flow to the venous pouch itself is rapid like that seen in traumatic
Discussion Classification
Spinal arteriovenous communication can be classified into spinal cord AVMs and AVFs, spinal dural AVFs, and extradural AVMs and AVFs according to the anatomic space 1-3. Among these lesions, the paravertebral groups are recognized as very rare entities. Paravertebral spinal vascular lesions are subcategorized into two main groups, isolated and associated. The isolated group is discriminated by paraspinal AVFs along the segmental nerve 4: vertebral436
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Table 1 Classification of Spinal AVMs/AVFs
Epidural/Paraspinal AVFs/AVMs #Isolated 1. paraspinal AVFs along the segmental nerve a. vertebrovertebral fistulas b. non vertebral segmental nerve fistulas 2. vertebral bone AVMs 3. slow-flow epidural AVFs w/ intradural reflux 4. other extradural AVFs / AVMs #Associated 1. metameric 2. systemic dysplasia Dural AVFs Intradural AVFs/AVMs #Isolated #Associated
or neurofibromatosis type I lesions. Shunt flow to the osseous component seemed to be relatively slower than that of the main shunts from the peripheral intercostal artery. The osseous vertebral nidus was presumed to be the result of a secondary sump phenomenon produced by the rapid flow in the main AVFs. Therefore, the present case showed a different flow pattern from the two cases of SOEAVFs reported by Suh, which were both slow flow shunts. The reason for the discrepancy of shunt speed between our case and that reported by Suh is unclear 5. An initial stage and advanced stage in the same region may be one of the possible explanations. The present case is considered the combined type of extradural AVF and associated secondary bone AVM. Symptoms
The etiology of paravertebral AVMs is reported to be congenital, spontaneous, traumatic, iatrogenic or systemic syndrome causing dysplastic vessels such as neurofibromatosis type I 11 , Elheros-Danlos-IV, fibromuscular dysplasia. Paravertebral spinal AVMs have been detected
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incidentally or by presentation with compressive myelopathy or venous congestive myelopathy. These lesions can also present with a subcutaneous pulsating mass in the paravertebral musculature, spinal canal deformity, cardiac failure or bleeding. In our case, the clinical manifestations were assumed to have resulted from three etiological factors: direct mechanical compression by dilated venous vessels, long-term venous hypertension and vascular steal phenomenon. Symptoms in SOEAVFs may start as radiculopathy, presenting as lumbago as shown in our case. A fistulous dilated vein can lead to radicular pain from mechanical compression of the spinal cord, spinal nerve root. It can contribute to the maldevelopment of the neighboring spine causing a bone defect. Numerous osseous and epidural branches of the intersegmental arteries as well as anastomosis with upper or lower segments or contralateral arteries explain why multiple arteries frequently feed these fistulas, located in the epidural space. Regurgitation into the perimedullary vein from paravertebral/epidural shunts frequently confirm symptomatic cases. In case of disturbance or steno-occlusion at the venous outlet, intradural regurgitation can also lead to spinal congestive circulation and syringomyelia as seen in our patient. Previous case series reported these morphological findings and already established the clinical mechanisms 12-21. The venous return of the main radiculomedullary circulation was not visible, perhaps because it was diluted by the venous return of the fistula or congestive venous hypertension similar to that in spinal dural AVFs. From an anatomical and embryonic perspective, paraspinal epidural AVFs and the cavernous sinus dural AVFs could be linked, since these are both osteodural in location. When looking at the difference in the venous structures of spinal and intracranial lesions, the absence of a dural venous sinus in the spinal region is obvious. Venous sinuses like vascular pathways within the dural sheath can hardly be considered the same entity as venous channels located within the epidural space. There are no venous dural sinuses at the sphenoid level and the spinal epidural venous plexus has the same appearance all along the notochord from the sacrum to the skull-base 1. Paraspinal Batson’s venous system is a valveless draining pathway. The epidural venous channels have rich axial and longitudinal anastomoses. Elevation of Batson’s venous pressure automatically interferes with 437
High-flow Paraspinal Osseous Epidural Arteriovenous Fistula
the spinal venous drainage, even though there is a systemic diffusion phenomenon as a result of elevated venous pressure. These hemodynamic changes may ultimately lead to right cardiac overload. Myelopathy in the present case seemed to be a late manifestation caused by longstanding venous hypertension of the epidural plexus without intradural reflux. Congestion of the medullary vein even without any retrograde drainage could explain the inability to visualize the medullary drainage, and account for the clinical symptoms. The main site of interference with cord function due to high-pressure blood flow in the coronal venous plexus was in the region of the spine where the fistula was located. Although the mechanisms underlying syringomyelia in paravertebral vascular malformation are not well understood, direct mechanical compression of the spinal cord or CSF pressure gradient change may be involved. The clinical significance of arterial steal was difficult to explain, but it might have been responsible for spinal cord symptoms, especially when the spinal medullary artery branched at the same level as the main shunts similar to that in the present case. Intervention
During the attempt at surgical resection of the present SOEAVF at the previous institute, the surgeon had considerable difficulty in controlling hemorrhage from the osseous AVMs component. We consider that endovascular embolization is the treatment of choice for SOEAVFs. Regarding arterial access, this case presented some suspected risk factors. The prominent flow into the shunts may preclude appropriate opacification of a radiculomedullary artery originating at the same level. Actually, the spinal medullary artery originated from Th10 in the present case. Although it was not recognized on earlier diagnostic images, the artery became apparent among the osseous vascular components during the third intervention. Embolization of the anterior spinal axis through the radiculomedullary branches originating at the same segmental level as the fistula must be avoided. Elaborate superselective catheterization to the feeding arteries and careful staged planning are indispensable to avoid catastrophic complications. Regarding the venous approach, the first problem was the vascular anatomy of the lesion itself. It might be difficult to visualize the exact drain-
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ing site on conventional angiography because of the rapid speed and high volume shunt flow through the fistula and overlapping venous structures. Occlusion of the draining vein without shunt closure might present a high risk of hemorrhage. In two similar cases of SOEAVF reported by Suh et Al, they described the fistula site as a round fistular nidus, which was the target of the transvenous coil embolization. For venous occlusion, coils can be used, giving the theoretical advantage of progressive occlusion. Technical difficulty in placing coils only in the dilated venous pouch was also suspected because of the irregular shape of the venous angioarchitecture in our diagnostic images. The second problem was more complex. Considering the risk of mass effect from the dilated vein compressing the spinal cord, we were concerned about that transvenous coil embolization would not improve the symptoms. These unusual features have important implications for treatment. In our opinion and based on our experience, although a single hole fistula is best treated using a detachable balloon, liquid embolic material, such as NBCA, is the most appropriate material for arterial embolization of complex spinal AVFs. As a permanent embolic agent, NBCA offers immediate and durable occlusion for high flow AVFs. Several technical adjuncts helped to control the flow during injection of the liquid embolic agent, simplifying the obliteration of the fistulas without migration of the embolization material into the venous system. Controlled hypotension during pure glue injection is routinely used in our institute. We also make a continuous pure NBCA column by continuously pushing very slowly using a 2.5cc syringe. Conclusion A patient with complex SOEAVF was presented. Transarterial glue embolization by multiple staged sessions achieved a good clinical and morphological outcome in our case. Endovascular glue intervention is a safe and effective treatment modality for this condition and should be the first choice of treatment. High-flow SOEAVF may be curable by carefully planned and staged intervention. In the present case, congestive myelopathy produced by elevation of Batson’s venous system was considered the main etiological factor.
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Yuo Iizuka, MD Department of Radiology Juntendo Urayasu Hospital Juntendo University, School of Medicine 2-1-1, Tomioka Urayasu pref. 279-0021 Chiba, Japan Tel.: 047-353-3111 Fax: 045-353-3138 E-mail: [email protected]
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