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ORIGINAL ARTICLE
Year : 2017  |  Volume : 29  |  Issue : 1  |  Page : 18-23

Treating intracranial dural arteriovenous fistulas with gamma knife radiosurgery: Asingle-center experience


1 Department of Neurosurgery, Neuro-Medical Scientific Center, Buddhist Tzu Chi General Hospital; Department of Surgery, Buddhist Tzu Chi General Hospital, Hualien, Taiwan
2 Department of Neurosurgery, Neuro-Medical Scientific Center, Buddhist Tzu Chi General Hospital, Hualien, Taiwan
3 Department of Neurosurgery, Neuro-Medical Scientific Center, Buddhist Tzu Chi General Hospital; School of Medicine, Tzu Chi University, Hualien, Taiwan

Date of Submission05-Aug-2016
Date of Decision08-Oct-2016
Date of Acceptance02-Nov-2016
Date of Web Publication3-Apr-2017

Correspondence Address:
Chain-Fa Su
Department of Neurosurgery, Buddhist Tzu Chi General Hospital, 707, Section 3, Chung-Yang Road, Hualien
Taiwan
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/tcmj.tcmj_4_17

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  Abstract 

Objective: We evaluated the effectiveness and safety of gamma knife radiosurgery (GKRS) for the treatment of intracranial dural arteriovenous fistulas (dural AVFs) over the past 10years. Materials and Methods: The records of 21patients diagnosed with dural AVFs between 2004 and 2014 and treated with GKRS were reviewed retrospectively. Complete obliteration (CO) was defined as total symptom relief plus confirmation through magnetic resonance imaging or conventional angiography. Results: The median follow-up was 70.5months (range 3–136months). Five patients underwent embolization (2 after GKRS). One patient underwent GKRS twice. The CO rate was 47%, and partial to CO rate was 88%. The complete symptom resolution rate was 77%, and all patients achieved partial to complete symptom resolution. The CO rates for Borden TypeI and TypeII/III dural AVFs were 66.7% and 25% (P=0.153), respectively, and complete symptom-free rates were 76.9% and 75.0% (P=1.000%), respectively. The median duration between initial GKRS and complete symptom resolution was 14.3months. The median treatment to image-free durations for Borden TypeI and TypeII/III dural AVFs were 25.9 and 60.4months (P=0.028), respectively, and treatment to symptom-free durations were 10.6 and 36.7months (P=0.103), respectively. One patient had a recurrent hemorrhage. Two patients experienced brain edema after stereotactic radiosurgery and one patient experienced cystic formation after GKRS. The morbidity rate was 19% (four patients) and there was no mortality. Conclusion: Treatment with GKRS for dural AVFs offers a favorable rate of obliteration. Patients with dural AVFs that are refractory or not amenable to endovascular or surgical therapy may be safely and effectively treated using GKRS.

Keywords: Arteriovenous fistula, Dural arteriovenous fistula, Gamma knife, Stereotactic radiosurgery


How to cite this article:
Wang GC, Chen KP, Chiu TL, Su CF. Treating intracranial dural arteriovenous fistulas with gamma knife radiosurgery: Asingle-center experience. Tzu Chi Med J 2017;29:18-23

How to cite this URL:
Wang GC, Chen KP, Chiu TL, Su CF. Treating intracranial dural arteriovenous fistulas with gamma knife radiosurgery: Asingle-center experience. Tzu Chi Med J [serial online] 2017 [cited 2018 Dec 14];29:18-23. Available from: http://www.tcmjmed.com/text.asp?2017/29/1/18/203689


  Introduction Top


An intracranial dural arteriovenous fistula (dural AVF), also known as a dural arteriovenous malformation, is a type of intracranial vascular malformation. Adural AVF is a connection between an intracranial artery and a dural venous sinus. The current treatment strategies for dural AVFs include microsurgical ligation, transarterial or transvenous embolization, stereotactic radiosurgery (SRS), and various combinations of these options [1],[2],[3].

There are two major classification systems for dural AVFs according to the location and drainage of the fistula, the Borden classification and the Cognard classification [4],[5]. The Cognard classification can be merged with the Borden classification according to cortical venous drainage [Table1] [6]. Carotid-cavernous (CC) fistulas, which connect the internal carotid artery and a cavernous sinus, have their own classification system. These fistulas are classified using the Barrow classification according to high-direct fistula flow or low-indirect fistula flow and the location of the fistula [Table2] [7]. Barrow TypeA CC fistulas are defined as high flow, with direct drainage from the internal carotid artery to a cavernous sinus, and are related to trauma; this type of fistula is beyond the scope of this study.
Table 1: Borden classification system of dural arteriovenous fistulas

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Table 2: Barrow classification system of carotid-cavernous fistulas

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In this article, we evaluate the initial presentation, clinical course, and outcome of dural AVFs at our hospital. Gamma knife radiosurgery (GKRS) is the major treatment modality for dural AVFs at our hospital because of patient preference, embolism technique limitations, and physician preference. Therefore, this article can serve as a reference for those interested in dural AVFs treated using GKRS and other SRS techniques.


  Materials and Methods Top


Study population

Patients enrolled in this study included those diagnosed with dural AVFs between 2004 and 2014 at Tzu Chi General Hospital, Hualien, Taiwan. Patients who did not have dural AVFs confirmed through angiography were excluded from the study. The study was conducted in accordance with the Declaration of Helsinki and was approved by the local ethics committee of Tzu Chi General Hospital, Hualien, Taiwan. (IRB 103-88-B) Informed written consent was waived because the study was a retrospective data analysis.

Data collection

The data collected included gender, age, initial symptoms, type of dural fistula, treatment strategy, radiosurgery dose, volume treated using GKRS, imaging results, length of patient follow-up, and outcome. Complete obliteration (CO) was defined as no dural AVFs observed on either magnetic resonance imaging (MRI) or angiography during follow-up. Partial obliteration was defined as regression or decreasing of dural AVFs nidus or venous drainage on MRI or angiography, mainly defined by the radiologist. Partial symptom resolution was defined as decreasing symptoms including tinnitus, proptosis, or chemosis according to patient report and physician observation. The treatment to image-free duration was defined as the duration between the patient receiving radiosurgery and CO confirmed through imaging. The treatment to symptom-free duration was defined as the duration between the patient receiving radiosurgery and the time at which the patient became symptom-free.

Radiosurgery methods

After local anesthesia had been applied, a Leksell stereotactic frame (Elekta Instrument AB, Stockholm, Sweden) was rigidly fixed on the patient's head, following which digital subtraction angiography images and contrast-enhanced brain MRI (1–2-mm thickness) were acquired. These images were sent to a GammaPlan computer (Elekta Instruments AB, Stockholm, Sweden) and the region of interest was planned [Figure1]. A201 cobalt-60 source gamma knife system (Model C, Elekta Instruments) was used. After complete planning, the patient's head and frame were fixed in a collimator helmet and the treatment was performed until the conformal field encompassed the treatment volume. For dural AVFs, the treatment dose ranged from 13 to 18Gy at an isodose level of 50%. The dose was determined on the basis of the target volume (the larger the volume, the smaller the dose) and whether critical organs (e.g.,optical apparatus or brain stem) were near the radiation target. For abnormal AVFs which drained into the sinus wall, the target was along the involved sinus wall [8]. Arterial feeders and cortical drainage veins were not considered treatment targets.
Figure 1: Digital subtraction angiogram superimposed on magnetic resonance images showing the dose planning for radiosurgery. The treating marginal dose level (inner isodose line) covers the border of the cavernous sinus

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Statistical analysis

SPSS 18 (IBM Corporation, Armonk, NY, USA) was used as the statistical analysis tool. Univariate categorical analyses were conducted using the Pearson Chi-square and Fisher's exact test. Univariate continuous variable analyses were conducted using Student's t-test. Kaplan–Meier survival analysis was used to calculate the treatment to symptom-free and treatment to complete image-free durations. Avalue of P<0.05 was considered statistically significant.


  Results Top


Margin dose and treated volume using gamma knife radiosurgery

The median follow-up was 70.5months (range 3–136months). Thirteen of the 21patients treated had Borden TypeI and 8 had Borden TypeII/III dural AVFs (Borden II =7; Borden III =1) [Table3]. The cavernous sinus was the most common location of dural AVFs (13patients), followed by the superior sagittal sinus and the transverse sinus [Table4]. Thirteen patients had CC fistulas and eight patients had non-CC fistulas. The average dose applied was 15.8Gy (range =13–18Gy). The average treated volume was 9.76mL. Patient's age ranged from 14 to 79years (mean: 56.3years). Apulsatile bruit was the most common initial symptom [Table5].
Table 3: Borden type classification of the 21 patients

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Table 4: Locations of dural arteriovenous fistulas of the 21 patients

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Table 5: Initial symptoms and presentations of the 21 dural arteriovenous fistulas patients

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Treatment outcome

Five patients underwent embolization (2 after gamma knife) and one patient received a second radiosurgery [Table6]. Four patients did not have follow-up images and thus were excluded from the CO rate calculation. The CO rate was 47%, and the partial to CO rate was 88%. The complete symptom resolution rate was 77%, and all patients achieved partial to complete resolution of their symptoms [Table7]. The CO rates for non-CC fistulas and CC fistulas were 66.7% and 62.5% (P=0.347), respectively. The CO rates for Borden TypeI and Borden TypeII/III dural AVFs were 66.7% and 25% (P=0.153), respectively, and the complete symptom-free rates were 76.9% and 75.0% (P=1.000%), respectively. The median duration between initial GKRS and complete symptom resolution was 14.3months. The median treatment to image-free durations for Borden TypeI and Borden TypeII/III dural AVFs were 25.9 and 60.4months (P=0.028), respectively, and the median treatment to symptom-free durations were 10.6 and 36.7months (P=0.103), respectively [Figure2]. One patient had a recurrent hemorrhage. Two patients experienced brain edema after SRS and one patient experienced cystic formation after GKRS. The morbidity rate was 19% (four of 21patients) and there was no mortality.
Table 6: Gamma knife radiosurgery margin dose and treated volume in 21 patients with dural arteriovenous fistulas

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Table 7: Treatment results of dural arteriovenous fistulas after stereotactic radiosurgery

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Figure 2: The left Kaplan–Meier curves showing the median treatment to symptom-free durations for Borden Type I and Borden Type II/III dural arteriovenous fistulas (10.6 vs. 36.7 months, P = 0.103). The right Kaplan–Meier curves showing the median treatment to image-free durations for Borden Type I and Borden Type II/III dural arteriovenous fistulas (25.9 vs. 60.4 months, P = 0.028)

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  Discussion Top


GKRS for dural AVFs has been shown to be effective in many studies [9],[10],[11]. In a recent systemic review [6] of 19 articles and 743patients, the mean CO rate for dural AVFs after GKRS treatment was 63%. In our study, we had a CO rate of 47%. The short follow-up duration in the present study might have contributed to the inferior obliteration rate as endothelial proliferation in response to SRS might occur gradually. In one study, 41% of patients treated with SRS achieved CO after 21months [12]. Therefore, if we exclude patients with <6months of follow-up from the present study, the CO rate was 53%. In addition, all 21patients showed partial to complete symptom resolution, suggesting that SRS is effective in treating dural AVFs, especially with regard to symptom control.

Borden TypeII/III AVFs have cortical venous drainage and are considered to carry a higher risk of hemorrhage and inferior GKRS treatment response [6],[13],[14],[15]. Similar results were observed in our study. The CO rate for Borden TypeI AVFs was 66.7% and that for Borden TypeII/III AVFs was 25%, a nonsignificant difference (P=0.153). Moreover, it took more time for Borden TypeII/III AVFs to achieve CO (25.9months for Borden TypeI and 60.4months for Borden TypeII/III, P=0.028). Only one patient who initially presented with hemorrhage in our study was classified as having Borden TypeII AVFs in the transverse sinus. Although CO was not optimal after GKRS for Borden TypeII/III dural AVFs, this treatment was effective in symptom resolution in both groups (76.9% complete symptom resolution for Borden TypeI and 75.0% for Borden TypeII/III, P=1.000). In contrast, we found no difference in the CO rate between the CC fistula and non-CC fistula groups (66.7% vs. 62.5%, P=1.000). Similar results were presented in another study [6]. The results might indicate that indirect typeCC fistulas are dural AVFs that occur in the cavernous sinus.

Surgery for dural AVFs has been proven effective [16],[17],[18]. The evolving technique of endovascular embolism has been used both in combination with surgical treatment [12],[19] and alone as a less invasive option. Recently, GKRS has been used to treat dural AVFs in combination with endovascular embolization [12],[20],[21]. Many have reported that GKRS alone is effective in treating dural AVFs, especially for controlling symptoms, and our experience showed the same results [6],[9],[22]. The major advantage of GKRS is that it is a relatively noninvasive procedure with a low risk of complications. However, the major concern with GKRS alone in treating dural AVFs is that it takes longer to achieve CO [12],[23]. In our study, the median GKRS to image-free duration was 44.9months and the median GKRS to symptom-free duration was 14.3months. Many patients had significant clinical improvement in symptoms despite images that showed remaining dural AVFs. [Figure3] shows a patient who presented with chemosis and proptosis and had complete symptom relief 2years after treatment. [Figure4] shows a patient who had Borden TypeII dural AVFs in the sigmoid and sagittal sinus and achieved CO after treatment. For Borden TypeII/III AVFs, which carry a higher risk of cerebral hemorrhage, endovascular embolization combined with GKRS might be a better choice in terms of immediate reduction in the rate of hemorrhage and improvement of clinical symptoms. This combined approach could also achieve long-term CO [9].
Figure 3: A 55-year-old woman with a left side indirect type carotid-cavernous fistula had chemosis and proptosis before gamma knife radiosurgery (a and b). Complete remission of the patient's symptoms and signs 2 years after gamma knife radiosurgery treatment (c and d)

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Figure 4: Contrast-enhanced magnetic resonance images from a 52-year-old woman with Borden Type II dural arteriovenous fistulas in the sigmoid and sagittal sinus. She received gamma knife radiosurgery in 2011 (a) and follow-up images showing gradual resolution of dural arteriovenous fistulas gamma knife radiosurgery 1 year (b) and 4 years (c) after treatment

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  Conclusion Top


Gamma knife surgery alone for the treatment of dural AVFs is effective and safe. Dural AVFs with cortical venous drainage (Borden TypeII/III) require more time to achieve a treatment response, a factor that strongly influences the CO rate. However, the rate of complete symptom relief was equally good in Borden TypeI and Borden TypeII/III dural AVFs.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
  References Top

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