Gamma Knife Radiosurgery: The Gold Standard Treatment for Intracranial Dural Arteriovenous Fistulas without Cortical Venous Drainage
Correspondence Address: Source of Support: None, Conflict of Interest: None DOI: 10.4103/0028-3886.293482
Source of Support: None, Conflict of Interest: None
Keywords: Dural arteriovenous fistula, Gamma Knife, radiosurgery
Intracranial dural arterio-venous fistulas (DAVFs) are pathologic shunts between dural arteries and dural venous sinuses and/or cortical veins. DAVFs account for 10%–15% of intracranial arteriovenous malformations. DAVFs are distinguished from parenchymal or pial arteriovenous malformations by the presence of a dural arterial supply and the absence of a parenchymal nidus. Their detection rate in adults is 0.16 per 100,000 per year.
Their clinical spectrum ranges from asymptomatic presentation to aggressive neurological symptoms. More malignant presentation, which includes intracranial hemorrhage, is seen in patients harboring DAVF with retrograde cortical drainage.,,,,,, The DAVFs are classified in most part according to the pattern of venous drainage, because this is the feature that most influences the natural history of the lesion.,, Endovascular therapy is currently the most common treatment approach for DAVFs as it has immediate fistula obliteration while it takes at least 6 months for complete obliteration of a fistula following Gamma Knife radiosurgery (GKS). However, GKS is emerging to be a suitable first-line treatment option for DAVF, especially for DAVF without cortical venous drainage (CVD).,,, The aim of this study is to evaluate the outcome of GKS in the treatment of DAVF without CVD.
After obtaining the required ethical clearance from the concerned body of our institution, all patients admitted in the department of Neurosurgery, AIIMS, New Delhi and who underwent GKS for intracranial DAVF without CVD over 10 years (Jan 2007 to Dec 2016) were included in the study. Their demographic profile, clinical presentation, imaging details, GKS details, and follow-up clinical status were obtained retrospectively from available medical records.
We categorized the clinical presentation of the patients into hemorrhagic (aggressive) and nonhemorrhagic (intermediate or benign) groups. Hemorrhagic (aggressive) group consisted of patients who presented with intracranial hemorrhage with or without progressive dementia, altered sensorium, and/or progressive motor deficits. Nonhemorrhagic (intermediate or benign) group had patients who presented with transient ischemic attack, seizures, cranial nerve deficits, diplopia, facial nerve palsy, glaucoma, or decreased visual acuity which was categorized in intermediate severity. Benign symptoms included tinnitus, atypical headaches, dizziness, proptosis, and chemosis.
Pre GKT MRI/CT were assessed for hemorrhage, parenchymal edema, evidence of hydrocephalus or infarction. Cerebral angiograms were studied to discern the location, nature, angioarchitecture, presence of cortical venous drainage and to classify the DAVFs according to Borden, Cognard, and Barrow classification.,, GKS details included maximum dose (Gy), margin dose (Gy), target volume (cm3), and intra/post GKS complications. Clinical follow-up, along with radiological assessment using MRI every 6 months was done after GKS. DSA was performed once MRI strongly suggested obliteration of DAVF. Patients who had a clinical follow-up of less than 1 year were excluded from the study.
After the Leksell stereotactic frame had been affixed to the patient's head under local anesthesia, the patient underwent stereotactic imaging so that we could obtain precise information on the shape, volume, and 3-dimensional coordinates of the DAVF. MR imaging was used in combination with biplanar angiography. From Jan 2007 to July 2011, GKS was done using GammaPlan 5.34, on Leksell Gamma Knife model B (Eleckta AB, Sweden). Since July 2011, Leksell GammaPlan 5.10 on Leksell Gamma Knife Perfexion (Elekta AB, Sweden) is being used. On angiographic images obtained during early to late arterial phases, the sites at which dural arteries drain directly into the dural sinus were targeted and treated with radiation dose decided by the treating neurosurgeon.
Patient characteristics-GKS group
There were a total of 15 patients who underwent GKS from 2005 to 2016 for DAVF and had a follow-up of more than 1 year. 10 patients had CVD and were excluded from this study. The remaining 5 patients who had DAVF without CVD were included the study. There were 4 males and 1 female with the male to female ratio being 4:1. The mean age was 44.8 years (range: 16 years to 61 years). 4 underwent primary GKS, while 1 underwent secondary GKS as he had a previous failed embolization. None of the patients had a history of any coagulation abnormality, sinus infection, or significant head trauma.
No patient had clinically aggressive presentation or hemorrhage at presentation. 2 patients had clinically intermediate presentation; one had an episode of transient ischemic attack and another had an episode of seizure. 3 patients had clinically benign presentation, 1 had pulsatile tinnitus, 1 had chemosis with proptosis, and 1 had headache as the only symptom.
Cerebral digital subtraction angiography (DSA) was done in all 5 patients prior to GKS. Locations of treated DAVFs included the following: falcotentorial region in 2 patients, transverse-sigmoid junction, cavernous sinus, and posterior frontal in 1 patient each. As per Borden classification, all were type I. As per Cognard classification, 1 was type 1 and 4 were type 2A. The single case of cavernous sinus DAVF was Barrow type D.
Gamma Knife details
The mean target volume was 0.492 cm3 (range: 0.26 cm3 to 0.66 cm3). The mean maximum radiation dose was 50.22 Gy (range: 50 Gy to 50.6 Gy). The mean margin dose at 50% isodose level was 25 Gy in all the 5 patients.
The mean follow-up duration was 71 months (range: 36–84 months). Post GKS DSA was done in all 5 patients at a mean duration of 24 months post GKS (range: 12 months–36 months). Clinical improvement was reported during the last follow-up in all 5 patients. Complete obliteration of fistula was observed in all 5 patients (100%). No patient had a latency interval hemorrhage post GKS. There was no complication related to GKS in any patient.
A 16-year-old female presented with left-sided pulsatile tinnitus for 6 months. She was evaluated by ENT department of another institution, where her MRI and MR angiography were done which revealed a left transverse-sigmoid junction DAVF. She underwent cerebral angiography which confirmed a left transverse-sigmoid junction DAVF with feeders from left middle meningeal, left occipital, bilateral meningohypophyseal trunk, and posterior meningeal branch of bilateral vertebral arteries [Figure 1]. The DAVF was identified and targeted based on MRI and DSA images [Figure 2] and [Figure 3] and 25 Gy was given to the 50% isodose line. The patient had complete resolution of tinnitus at 6 months. Post GK MRI was done at 1 year which revealed complete absence of flow voids. Complete obliteration of DAVF was confirmed on DSA done 2-year post GKS [Figure 2]. The patient is under regular follow-up and is doing well.
The rarity of DAVFs, availability of embolization and surgery as established treatment modalities, and the prolonged obliteration time with GKS have led to GKS as the last modality of treatment especially for DAVF with CVD. However, GKS is emerging to be a suitable alternative treatment option for DAVF.,,,,,,, This study demonstrated the effectiveness and safety and noninvasive benefits of GKS for the treatment of DAVFs without CVD.
It is well recognized that DAVFs with CVD have a significantly greater risk of hemorrhage compared with those without CVD. Söderman et al. reported a 1.5% annual risk of hemorrhage in 53 patients with unruptured DAVFs with CVD. In the same study, this risk increased to 7.4% per year for those with ruptured DAVFs. Strom et al. reported a similar annual hemorrhage rate of 1.4% in 17 patients harboring DAVFs with CVD without prior hemorrhage. The risk increased to 7.6% in those with DAVFs with CVD who presented with hemorrhage or nonhemorrhagic neurological deficit. Detailed analyses by Gross and Du of published studies found 6% and 10% annual hemorrhage rates for Borden Types II and III DAVFs, respectively, in contrast to an annual hemorrhage rate of 0% for Borden Type I DAVFs. Although an annual hemorrhage rate of 3% for unruptured DAVFs with CVD was found in their study, the rate increased to 46% per year for ruptured DAVFs with CVD. The recurrence of bleeding can occur within the first few weeks following the initial hemorrhage. Duffau et al. observed a rebleeding rate of 35% within the first 2 weeks after the initial hemorrhage. Significant mortality rates of up to 10.4% annually have been associated with the persistence of CVD. Given the high morbidity and mortality rates observed in untreated DAVFs with CVD, all patients harboring DAVF with CVD should be treated. For patients harboring DAVFs without CVD, the decision to treat should be based on the severity of symptoms. Close observation should be recommended to patients with nondisabling symptoms, whereas GKS and/or endovascular embolization should be reserved for those with intractable symptoms.
In the studies by Cifarelli et al. and Hanakita et al., absence of CVD was found to be a significant factor favoring obliteration of DAVF by GKS. In the systematic review by Chen et al., concerning stereotactic radiosurgery for intracranial DAVF, complete obliteration in DAVFs with and without CVD was observed in 56% and 75% of patients, respectively, and the difference was statistically significant (P = 0.03). In our study, we observed 100% obliteration rate of DAVF without CVD post GKS.
Studies concerning GKS for intracranial DAVF by Cifarelli et al., Hanakita et al., and Dmytriw and Schwartz have found clinical improvement in patients ranging from 66% to 86%. Our study has shown clinical improvement in 100% of the patients who received GKS for DAVF without CVD.
The systematic review concerning SRS for intracranial DAVF by Chen et al. included nineteen studies treated with SRS. The mean obliteration rate was 63%. The obliteration rates of DAVF post embolization varied from 60%–80% in various series.,,,, In our study, complete obliteration of DAVF was observed in 100% of the patients who received GKS for DAVF without CVD.
Studies by Cifarelli et al., Chen et al., Hanakita et al., and Dmytriw and Schwartz have all mentioned the safety of GKS in the treatment of intracranial DAVF with low complication rate. In our study, no GKS-related complication was seen in any patient. However, embolization, being an invasive procedure, carries high risk of multiple serious complications which have been reported in up to 25% of cases.,, These include reflexive bradyarrhythmia, posterior fossa infarction, hemifacial hypoesthesia, hemifacial palsy, microcatheter gluing, Onyx migration, intraparenchymal hematoma, delayed cerebral venous infarction, etc., There also have been multiple reports of recurrence in apparently cured DAVF post embolization. Onyx, the material commonly used during embolization of DAVF, has been thought to cause significant inflammation within the vasculature, particularly with treatment of cavernous carotid fistulas in which the surrounding cranial nerves are often irritated, resulting in various cranial nerve palsies. There also have been reports of DAVF formation at a distant site post embolization.
The average latency interval for the fistula closure was 2 years in our experience. DAVF obliteration may occur even sooner than other vascular malformations such as arteriovenous malformations.
DAVF location is another significant factor that affects both the rate of obliteration and symptomatic improvement., In our series, only 1/5 patient has cavernous sinus DAVF. This highlights that not only the cavernous sinus DAVFs but also DAVFs at other locations respond well to GKS.
Gamma Knife surgery is the most effective and the safest treatment modality for dealing with DAVFs without CVD. Instead of reserving it as the last resort for patients with DAVF without CVD, it should be considered as the gold standard treatment for DAVFs without CVD.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
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Conflicts of interest
There are no conflicts of interest.
[Figure 1], [Figure 2], [Figure 3]