Multiple Dural Arteriovenous Fistulas

Transcription

1 Multiple Dural Arteriovenous Fistulas Satoshi USHIKOSHI, Yoichi KIKUCHI*, Kiyohiro HOUKIN**, Hisatoshi SAITO, and Hiroshi ABE** Sapporo Azabu Neurosurgical Hospital, Sapporo; Departments of *Radiology and **Neurosurgery, University of Hokkaido School of Medicine, Sapporo Abstract Four patients with multiple intracranial dural arteriovenous fistulas (DAVFs) at separate sites were treated by endovascular techniques (transarterial and/or transvenous embolization), surgery (excision or isolation), radiotherapy, or combinations, according to the pathophysiological condition. All lesions in two patients were obliterated completely without neurological deficit. There were residual fistulas af ter the treatment in two patients, but these were low-grade lesions without retrograde cortical venous drainage, and marked clinical improvement was obtained. Planning of treatment strategies for multiple DAVFs requires careful analysis of the venous drainage from the affected sinuses and cerebral hemodynamics. Key words: dural arteriovenous fistula, multiple lesions, endovascular therapy Introduction Intracranial dural arteriovenous fistulas (DAVFs) are currently considered to be acquired abnormal ar teriovenous connections located within the wall of a dural sinus.3,1,',17) Widely spreading contiguous fistu las, such as those involving the transverse-sigmoid sinuses, are not infrequent, but multiple DAVFs at separate sites are relatively rare. 1, 5,6,10,12,13,15,16.20) The incidence of multiple lesions was 6.7% in a large number of patients with DAVF.1j We treated four patients with multiple DAVFs over the last 12 years, and describe the pathogenesis and treatment strate gies for multiple DAVFs. Table 1 Classification of dural arteriovenous fistu las according to venous drainage Materials and Methods The clinical presentation, radiological findings, treatment, and outcomes of the four patients with multiple DAVFs treated at our hospital were rev iewed. Each lesion was classified according to the revised Djindjian classification') based on the type of venous drainage (Table 1). Abnormalities of dural sinuses were also examined. Treatment strategies, in cluding endovascular techniques, surgery, and radiotherapy, were determined individually based on the pathophysiology. Transarterial embolization was performed using polyvinyl alcohol (PVA) parti cles or n-butyl 2-cyanoacrylate (NBCA). Trans venous embolization was performed from the femoral vein, using platinum coils as the embolic materials. Received September 29, 1997; Accepted April 13, 1998 Author's present address: S. Ushikoshi, M.D., Department of Radiology, University of Hokkaido School of Medicine, Sapporo, Japan.

2 Fig. 2 Case 2. T1-weighted magnetic resonance image, sagittal view (A), revealing thrombosis of the superior sagittal sinus (arrow). Left external carotid angiogram, frontal view (B), showing the superior sagittal sinus dural arteriovenous fistula (DAVF). Right vertebral angiogram, frontal view (C), showing the right transverse sinus DAVF, located in a separate venous con partment from the sinus lumen (arrowheads), and the right sigmoid sinus DAVF. Right com mon carotid angiogram, lateral view in the venous phase (D), showing that the superior sagit tal sinus distal to the fistula (thick arrows) does not contribute to the normal venous drain age. The vein of Labbe drains anterogradely into the right transverse sinus (arrowheads), and the blood flow of the right transverse sinus goes into the left transverse-sigmoid sinus (arrow). Right common carotid angiograms, lateral view in the arterial (E) and venous phases (F), showing complete obliteration of all lesions after the transvenous embolization and no deterioration of the normal venous drainage. Anterograde flow of the vein of Labbe is patent (arrowheads). the dural wall of the sinus or stimulates the develop ment of such shunts through the recanalization process. Recently, the importance of both sinus thrombosis and venous hypertension was demon strated in the development of DAVF in animal models.') Moreover, an animal experimental study showed that only venous hypertension, without thrombosis, can cause the development of ar teriovenous shunts.") Based on these experimental results and some histological evidence,',") the elevat ed venous pressure in a dural sinus or a vein is proba bly transmitted directly to the vasa vasorum-like capillaries and arterioles in the sinus or venous wall via a retrograde route, resulting in the formation of arteriovenous shunts. Sinus thrombosis may be in volved by causing venous hypertension or activating angiogenetic factors during the recanalization process."',") The pathogenesis of multiple DAVFs is difficult to determine, as these lesions may develop at different sites simultaneously by the same process, or the first DAVF may induce development of the others. Case 1 had a second DAVF in the previously occluded si nus, and located downstream to the first DAVF Case 2 developed a DAVF following thrombosis of the superior sagittal sinus, located upstream to the

3 Fig. 3 Case 4. Right external carotid angiogram, lateral view (A), showing the superior sagittal si nus dural arteriovenous fistula (DAVF) and the right transverse sinus DAVF with reflux into the cortical veins, and severe stenosis of the right jugular vein (arrow). Right internal carotid angiogram, lateral view in the venous phase (B), demonstrating prolonged circulation time and under opacification of the cerebral venous system. Left external carotid angiogram, later al view (C), showing another DAVF in the left sigmoid sinus and reflux of shunt flow into the cortical veins and the straight sinus. Severe stenosis of the left jugular vein (arrow) and occlu sion of the left transverse sinus (arrowhead) are also present. Right external carotid angio gram, lateral view (D), after transarterial embolization and transvenous embolization of the DAVFs in the superior sagittal sinus and the left sigmoid sinus, demonstrating that the resid ual right transverse sinus DAVF still shows reflux into the vein of Labbe (arrows) and the straight sinus (arrowhead). Left common carotid angiogram, frontal view (E), after surgical isolation, showing complete obliteration of the DAVFs in the superior sagittal sinus and the left sigmoid sinus, and a small residual DAVF in the right transverse sinus without retro grade venous drainage. Right internal carotid angiogram, lateral view in the venous phase (F), demonstrating improved cerebral circulation time and anterograde flow of the vein of Labbe (arrows) and the straight sinus (arrowhead). other two DAVFs. There are several explanations for the development of multiple DAVFs. The venous drainage due to an established DAVF may cause tur bulent flow or stagnation in the distant venous si nus, resulting in thrombosis of the sinus and develop ment of other DAVFs. Thrombosis of a dural sinus at several sites caused by, for example, hypercoagula tive state may also lead to the development of multi ple DAVFs. However, sinus thrombosis could not be demonstrated in Cases 3 and 4, although severe ste nosis of both jugular veins was recognized in Case 4. Two interesting cases of development of new DAVF during the follow-up period for the initial DAVF have been reported.') As only venous hypertension unaccompanied by sinus thrombosis can cause the development of DAVF, elevated sinus pressure caused by initial DAVF or some other pathogenesis can result in the formation of multiple new DAVFs at other sites. Currently, endovascular techniques are the first

4 choice for most DAVFs ,14,18) Transarterial emboli zation is very useful for reducing the shunt flow, but complete cure is usually difficult to attain due to the recruitment of other feeding vessels and recanaliza tion of the embolized vessels when particulate embol ic materials are used. Recently, transvenous emboli zation was proposed as an effective and curative treatment.',") However, venous infarction may oc cur after occlusion of dural sinuses or cortical veins which contribute to the normal venous drainage or are not exposed to the high venous pressure. The de cision to perform transvenous embolization should be based on the patient's clinical history and the risks of the treatment. From this point of view, grad ing systems for classifying DAVF have been proposed based on the venous drainage pattern. 2.5,14) The most appropriate candidates for transvenous embolization are patients with cortical venous drainage and normal veins of brain tissue not drain ing into the affected sinus. 2,5,'.11,14.18) Patients with multiple DAVFs present with an even more complex state. Venous hypertension caused by one DAVF might be enhanced by the presence of the other DAVF. The treatment of multi ple lesions must consider whether multiple sinus oc clusion can be tolerated, especially when both the sagittal and the transverse-sigmoid sinuses, or the bilateral transverse-sigmoid sinuses are affected, as in our Case 4. Previously, three cases of combined sagittal and lateral sinus DAVF were treated with ex cellent clinical outcomes, and the effectiveness of staged deliberate occlusion of the affected sinuses was emphasized.") Treatment of DAVF should at tempt to decrease venous hypertension and improve the cerebral hemodynamics, not to obtain complete obliteration of the fistulas.',",") Examination of the venous drainage from the affected sinuses and brain tissue is most important, and the appropriate strategy should be devised accordingly. Our and previous experience suggests that hazardous multi ple DAVFs and clinical symptoms can be controlled successfully by staged obliteration of the fistulas. Changes in cerebral hemodynamics and clinical presentations should be investigated carefully at each step for determination of the next step of treatment.15) Persistent low-risk lesions without retrograde cortical venous drainage do not always require treatment, although the natural history of such lesions is not yet well known. References 1) Barnwell SL, Halbach VV, Dowd CF, Higashida RT, Hieshima GB, Wilson CB: Multiple dural ar teriovenous fistulas of the cranium and spine. 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5 17) Nishijima M, Takaku A, Endo S, Kuwayama N, Koizumi F, Sato H, Owada K: Etiological evaluation of dural arteriovenous malformations of the lateral and sigmoid sinuses based on histopathological ex aminations. J Neurosurg 76: , ) Roy D, Raymond J: The role of transvenous emboliza tion in the treatment of intracranial dural ar teriovenous fistulas. Neurosurgery 40: , ) Terada T, Higashida RT, Halbach VV, Dowd CF, Tsuura M, Komai N, Wilson CB, Hieshima GB: De velopment of acquired arteriovenous fistulas in rats due to venous hypertension. J Neurosurg 80: , ) Yamashita K, Taki W, Nakahara I, Nishi S, Sadato A, Kikuchi H: Development of sigmoid dural ar teriovenous fistulas after transvenous embolization of cavernous dural arteriovenous fistulas. AJNR Am J Neuroradiol 14: , 1993 Address reprint requests to: S. Ushikoshi, M.D., Depart ment of Radiology, University of Hokkaido School of Medicine, North-15, West-7, Kita-ku, Sapporo , Japan. -