Gamma Knife Radiosurgery for Brain Vascular Malformations

A. Niranjan, H. Kano, L. D. Lunsford

• Editore: S. Karger
• Anno: 2012
• ISBN:
  9783805596206
• Argomento: Medicina
• Categoria: Neurochirurgia

Clinical outcomes of brain vascular malformation have been greatly improved by advances in microsurgery, endovascular techniques and stereotactic radiosurgery. Radiosurgery has proven to be the least invasive technique and is associated with documented long-term success. The papers in this volume present the experience of leading brain vascular malformation specialists who describe the outcome of radiosurgery for arteriovenous malformations, cavernous malformations and dural arteriovenous fistulas. These reviews expand the knowledge of the role of stereotactic radiosurgery alone or in combination with other treatment modalities. Evidence-based guidelines are included in each section to provide a summary of the current management strategies. This unique publication includes additional data that will further define the long-term benefit and risks of radiosurgery for these often complex vascular disorders and makes valuable reading for neurosurgeons, neurologists and endovascular specialists interested in an excellent summary of more than 30 years of accumulated experience in the management of brain vascular malformations.

Niranjan A, Kano H, Lunsford LD (eds): Gamma Knife Radiosurgery for Brain Vascular Malformations.
Prog Neurol Surg. Basel, Karger, 2013, vol 27, pp 176-194 (DOI: 10.1159/000341793)

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Intracranial Dural Arteriovenous Fistulas: Natural History and Rationale for Treatment with Stereotactic Radiosurgery

David Hung-Chi Pan^a,c · Hsiu- Mei Wu^b,c · Yu-Hung Kuo^a,d · Wen-Yuh Chung^a,c · Cheng-Chia Lee^a,c · Wan-You Guo^b,c

Departments of ^aNeurosurgery and ^bRadiology, Taipei Veterans General Hospital, and ^cSchool of Medicine, National Yang-Ming University, Taipei, Taiwan, ROC; ^dDivision of Neurosurgery, Albany Medical Center, Albany, N.Y., USA

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Abstract

Dural arteriovenous fistulas (DAVFs) are abnormal arteriovenous communications within the dura. The symptoms depend on their location and the pattern of the venous drainage. Patients with cavernous sinus DAVFs often present with ocular manifestations such as exophthalmos, chemosis and diplopia. Patients with transverse or sigmoid sinus DAVFs frequently experience headache and tinnitus on the affected side. DAVFs with anterograde sinus or cortical venous drainage (CVD) have been clinically regarded as benign, whereas DAVFs with retrograde CVD are considered aggressive in behavior. Similar to other cerebral arteriovenous malformations, DAVFs can hemorrhage, with an estimated annual risk of approximately 1.8%. The recommended therapeutic intervention for a DAVF is dependent on the anticipated natural history of the lesion. Management options include surgical resection, embolization and radiosurgery. Radiosurgical treatment has been used for DAVFs in various locations including the anterior cranial fossa, cavernous sinus, transverse/sigmoid sinus, superior sagittal sinus and tentorium. We present an update on 321 DAVF patients treated at the Taipei Veterans General Hospital using Gamma Knife radiosurgery.The prescribed mean margin dose was 17.2Gy. In our series, 98% of patients had a stable or improved clinical condition after radiosurgery. Stereotactic radiosurgery using the Gamma Knife is a safe and effective alternative for the treatment of DAVFs.

Copyright © 2013 S. Karger AG, Basel

Intracranial dural arteriovenous fistulas (DAVFs) are abnormal arteriovenous communications within the dura, in which meningeal arteries shunt blood directly into the dural sinus or leptomeningeal veins [1, 2]. The incidence of DAVFs has been estimated at 5-20% of all intracranial vascular malformations [3-5]. DAVFs comprise only 6% of supratentorial vascular malformations whereas they constitute 35% of infratentorial malformations [6]. The mean age of presentation for a DAVF is 50-60 years of age with no sex preference, though there is a wide range seen [7, 8]. Unlike the more common intracerebral or parenchymal arteriovenous malformations (AVMs), DAVFs are thought to be acquired in origin due to inflammation, thrombosis or trauma of the dural sinus. However, in many cases the exact etiology and underlying disease are difficult to trace and those DAVFs are considered idiopathic [9, 10]. DAVFs most commonly occur in the regions of the cavernous sinus (CS), transverse/ sigmoid sinuses, tentorium/torcula, or cerebral convexities with drainage to the superior sagittal sinus [1, 11, 12].

A thorough understanding of DAVF hemodynamics requires a detailed cerebral angiographic investigation. Drainage of the venous flow from a DAVF can be ante-grade or retrograde through a dural sinus, through a cortical vein or both. The pattern of the venous drainage is not necessarily static though. Gradual alternation in the venous flow from antegrade to retrograde, and delayed recruitment of arterial feeders into the nidus (sump effect) have been observed in some patients [3, 8]. This is hypothesized to occur as a result of progressive sinus hypertension with redirection of the blood flow into cortical veins [2, 11, 13]. The gradual venous hypertension and reflux of the cortical veins may eventually predispose to the risks of cerebral hemorrhage and/or other neurological deficits [1].

Not all DAVFs demonstrate such a progressive clinical course though. Although not frequently seen, some DAVFs can regress and thrombose gradually resulting in a spontaneous cure [14, 15]. The factors predisposing to DAVF progression or involution have not been clearly clarified.

Natural Course

The clinical presentation of a DAVF is dependent on its location and pattern of the venous drainage. Patients with CS DAVFs often have ocular manifestations (exophthalmos, chemosis, visual impairment and diplopia). Those with lateral tentorial (transverse/sigmoid sinus) lesions frequently complain of headache and pulse-synchronous tinnitus on the affected side. DAVFs with anterograde sinus or cortical venous drainage (CVD) have been clinically regarded as benign, whereas DAVFs with retrograde CVD are considered aggressive in behavior [8, 16, 17]. In 1990, Awad et al. [1] reported a meta-analysis of 377 DAVFs and defined 100 aggressive cases as those with hemorrhages or progressive focal neurological deficits; the other 277 DAVFs were defined as benign cases. They concluded that no location of the DAVFs was immune from the aggressive neurological behavior. The factors that predict aggressive neurological presentation included leptomeningeal venous drainage, variceal or aneurysmal venous dilation, and galenic drainage of the DAVFs.

Similar to other cerebral AVMs, DAVFs can hemorrhage, with an estimated annual risk of approximately 1.8% [7]. Van Dijk et al. [17] in 2002 reported that persistence of the cortical venous reflux in DAVFs yields an annual hemorrhage rate of 8.1% and a mortality rate of 10.4%. Duffau et al. [18] reported a high risk of early rebleeding (35% within 2 weeks) after the first episode of hemorrhage, with graver consequences from the second bleed. Söderman et al. [19] in 2008 evaluated the hemorrhage rate in their 85 cases of DAVFs with retrograde CVD. They found a lower hemorrhage rate compared to those of the other previous reports. In their patients already presenting with an intracranial hemorrhage, the annual risk for the recurrent hemorrhage was 7.4% while in those patients not presenting with a hemorrhage, the bleeding rate was approximately 1.5% per year [19].

Classifications

Two main classification systems have been proposed. The Borden-Shucart system distinguishes DAVFs depending on the site of drainage and the presence of CVD [13]. Type I DAVFs drain directly into the sinus or meningeal veins with antegrade flow, whereas type II DAVFs have retrograde flow through the sinus into the subarachnoid veins. Type III DAVFs directly drain into the subarachnoid veins in a retrograde fashion.

The system of Cognard et al. [11] similarly separates DAVFs depending on the site of drainage and the presence of CVD, but also...