Subtotal Obliteration Research Articles

Gamma Knife Radiosurgery in Partially Embolised Arteriovenous Malformations: Management Dilemmas and Outcomes.

The role of Gamma Knife radiosurgery (GKRS) in partially embolized arteriovenous malformations (AVMs) has always remained a subject of debate. The aim of this study was to evaluate the efficacy of GKRS in partially embolized AVMs and to analyze factor that influence its obliteration. This was a retrospective study from a single institute performed over a period of 12 years (2005-2017). It included all patients who underwent GKRS for partially embolized AVMs. Demographic characteristics, treatment profiles, and clinical and radiological data were obtained during treatment and follow-up. Obliteration rates and factors affecting the same were sought and analyzed. A total of 46 patients with a mean age of 30 years (range: 9-60 years) were included in the study. Follow-up imaging was available for 35 patients either by digital subtraction angiography (DSA) or magnetic resonance imaging (MRI). We found complete AVM obliteration in 21 patients (60%): one had near total obliteration (>90% obliteration), 12 had subtotal obliteration (<90%), and one had no change in the volume following GKRS. Following embolization alone, an average of 67% of the AVM volume was obliterated which resulted in an average 79% final obliteration rate after Gamma Knife radiosurgery. Mean duration to complete obliteration was found to be 3.45 years (range: 1-10 years). There was a significant difference (P = 0.04) in the mean interval between embolization and GKRS among cases with complete obliteration (12 months) and those with incomplete obliteration (36 months). There was no significant difference (P = 0.49) in the average obliteration rate between the ARUBA-eligible unruptured AVMs (79.22%) and ruptured AVMs (79.04%). Bleeding after GKRS during the latency period had a negative impact on obliteration (P = 0.05). Other factors like age, sex, Spetzler-Martin (SM)-grade, Pollock Flickinger score (PF-score), nidus volume, radiation dose, or presentation before embolization had no significant influence on obliteration. Three patients had permanent neurological deficits after embolization and none after radiosurgery. Six out of nine patients (66%) presenting with seizures were seizure-free after the treatment. Hemorrhage was noted in three patients following combined treatment and were managed non-surgically. Obliteration rates in partially embolized AVM after Gamma Knife are inferior when compared to Gamma Knife alone; moreover with volume staging and/or dose staging being increasingly plausible due to the new ICON machine, embolization may be completely replaced. However we have shown that in complicated and carefully chosen AVMs, embolization followed by GKRS is a valid modality of management. This study represents a real-world picture of individualized AVM treatment depending on patient choices and resources available.

Abstract 1122‐000061: Initial Experience Using the Transvenous Embolization for Intracranial Arteriovenous Malformations in a Reference Endovascular Center

Introduction : Transvenous embolization (TVE) is used in cases of arteriovenous malformations (AVMs) with specific characteristics such as small size (&lt;3 cm), deep location, single draining vein and the absence of adequate feeders. High complete obliteration rates have been reported. Therefore, our study aimed to analyze our initial experience using the TVE for treatment of AVMs. Methods : Between May 2018 and January 2021, consecutive patients who underwent TVE of AVMs were selected. Demographics, radiological and clinical variables were collected. The modified Rankin Scale (mRS) was used to determine clinical outcomes and was dichotomized (good clinical condition: mRS £2; poor clinical condition: mRS &gt;2). Complete obliteration was defined as the total absence of the nidus and vein, subtotal obliteration was defined as the embolization of &gt;95% of nidus and partial obliteration was defined as the embolization of &lt;95% of nidus. Procedure‐related complications were defined as those that occurred during the procedure and were divided as intraoperative rupture and thrombosis. Results : Twenty‐one patients harboring 21 AVMs were evaluated. Fourteen patients (67%) were women. The mean age was 24.5 ± 14.1 years (7 – 48 years). A good preoperative clinical condition was present in 20 patients. Twenty AVMs were ruptured (95.2%). The most frequent locations were thalamus/basal ganglia in 6 patients (29%), followed by temporal/insular in 5 patients (24%). Spetzler‐Martin grades III, II and I were present in 11, 9 and 1 patients, respectively. The mean number of feeders was 2.1 per AVM. The feeders arised from the MCA in 9 cases, followed by PCA in 5 cases, ACA and AChoA in 3 cases, AICA in 2 cases, and ECA and PCom in 1 case, respectively. The mean number of veins was 1.3 per AVM. Deep venous drainage was present in 12 cases (57%). The mean size of the AVM nidus was 15.7 ± 7.8 mm (3.7 – 34 mm). Previous trans‐arterial embolization was done in 10 patients (47.6%). Pre‐embolization hematoma evacuation was done in 4 patients (19%). An immediate complete obliteration was achieved in 18 patients (85.7%), whereas a subtotal and partial obliteration were achieved in 2 and 1 patients, respectively. A poor post‐operative clinical condition occurred in 4 patients (20%). Procedure‐related complications occurred in 4 patients (20%): 3 cases with intra‐operative rupture of the AVM nidus and 1 case of a thrombus in the M1 treated with stent retriever. Mortality occurred in 3 patients (14.2%) of which two presented intra‐operative rupture with intracerebral hematomas that required decompressive craniectomy. One patient presented a post‐operative bleeding of the AVM nidus that required external ventricular drainage and decompressive craniectomy. Follow‐up angiography was done in 4 cases with total obliteration of all the cases (100%). Conclusions : The transvenous approach has emerged as an alternative to trans‐arterial approach with high grades of immediate total obliteration rates, but with potential procedure‐related complications. Thus, this technique should be used in selected cases in order to achieve complete cure rates.

Clinical and radiological response of aggressive dural arteriovenous fistula after combined glue embolization and hypofractionated helical TomoTherapy

AbstractPurpose:We reported the clinical and radiological outcome of an aggressive dural arteriovenous fistula (DAVF) after combined glue embolization and hypofractionated helical TomoTherapy (Hypo-HT).Materials and methods:Eleven patients whose radiological examinations are consistent with aggressive DAVF were treated with combined glue embolization and Hypo-HT 30–36 Gy in 5–6 fractions. The dosimetric analysis, clinical response and radiological imaging obliteration rate by magnetic resonance angiography or computed tomography angiography were investigated.Results:There were eight males and three females with a male and female ratio of 2·67. The mean age was 51·2 years old (range 37–69). Anatomical imaging sites of disease included transverse-sigmoid sinuses (n = 7), superior sagittal sinus (n = 3) and tentorium cerebelli (n = 1). The mean pitch and MF of treatment plans were 0·273 ± 0·032 and 1·70 ± 0·31, respectively. The average size of PTV were 15·39 ± 7·74 cc whereas the Reff,PTV was 1·50 ± 0·25 cm. The average Dmax and Dmin were 37·52 ± 3·34 and 31·77 ± 2·64 Gy, respectively. HI, CI and CI50 were 0·16 ± 0·06, 1·80 ± 0·56 and 7·85 ± 4·16, respectively. The Reff,Rx and Reff,50%Rx were 1·80 ± 0·24 and 2·90 ± 0·45 cm, respectively. The Reff between 50%Rx and 100%Rx was 1·10 ± 0·28 cm on average. With a mean follow up of 28·5 months (range 9–48), the complete recovery of symptoms was found in 72·7 % (eight patients) within 2–12 months after completion Hypo-HT. Partial recovery was reported in 18·2% (two patients). No clinical response was found in 9·1% (one patient). The total radiographic obliteration rate was 27·3% (three patients), subtotal obliteration was 27·3% (three patients) and partial obliteration was 45·4% (five patients).Conclusions:Satisfactory clinical response of aggressive DAVF was found in all treated patients by combining glue embolization and Hypo-HT. All dosimetric parameters were acceptable. We still need an extended follow up time to assess further radiographic obliteration rate and late side effects of the treatment.

Management of Residual Brain Arteriovenous Malformations After Stereotactic Radiosurgery

To assess outcome of residual brain arteriovenous malformation (BAVM) after stereotactic radiosurgery. Patients with residual BAVM 3 years after radiosurgery were retrospectively included. Demographics, angioarchitectural characteristics, complications, bleeding, and cure rates of patients with intervention or conservative management (i.e., observation) were compared. We analyzed characteristics of patients treated conservatively who achieved cure or still had persistent BAVMs during follow-up. The study included 87 patients including 5 patients with subtotal obliteration with a mean follow-up time of 33.7 ± 36.6 months. Of patients, 27 (31.0%) received subsequent treatment (radiosurgery, n= 23; microsurgery, n= 3; embolization, n= 1), and 60 (69%) were treated conservatively. After repeat SRS, 4 (14.8%) patients experienced symptomatic complications after the second treatment, and 7 (25.9%) experienced asymptomatic changes. Three (3.4%) patients, all of whom presented initially with a ruptured BAVM, experienced hemorrhage during follow-up. Subsequent treatment was effective with a complete cure of BAVM in 11 patients (40.7%). Complete resolution of the residual BAVM occurred in 15 (25%) patients treated conservatively. Complete obliteration of a significant number of residual BAVMs may occur 3-5 years after the first irradiation, whereas increased radiation dose associated with repeat SRS may lead to an increased risk of complications. The fact that the interval risk of bleeding decreased after SRS (especially for ruptured BAVM) lends further strength to the argument for a conservative management approach for residual BAVM 3-5 years after the first irradiation.

Stereotactic Radiosurgery for Dural Carotid Cavernous Sinus Fistulas.

We reviewed our 7-year experience to assess the efficacy of stereotactic radiosurgery (SRS) for dural carotid cavernous fistulas (DCCFs). We analyzed the clinical outcome, complications, and angiographic results. We performed a retrospective analysis of 18 consecutive patients with DCCFs treated by SRS alone using Gamma Knife between 2009 and 2015. Median target volume was 2.6 cm3 (range, 0.6-11.6 cm3), and median radiation dose to the target was 17 Gy (range, 14-19 Gy). Median follow-up period was 30 months (range, 6-65 months). Fifteen patients (83%) achieved total obliteration of the DCCF, and a subtotal obliteration of the DCCF was achieved in 3 patients (17%). Total obliteration rates after SRS were 53% at 1 year and 90% at 2 years. Twelve patients (67%) showed complete recovery from symptoms or signs, and 6 patients (33%) showed incomplete recovery. Improvement rates of neurologic function after SRS were 56% at 1 month, 72% at 3 months, and 94% at 6 months. None of the patients experienced radiation-related complications. A univariate analysis revealed that absence of hypertension (P= 0.025), seizure (P= 0.025), and cortical venous drainage (P= 0.013) were significantly associated with symptoms improvement. SRS for DCCFs offered a high obliteration rate with low risk of radiation-induced complications. In patients with benign DCCFs that are not amenable to embolization or microsurgery, SRS is a safe and effective treatment for complete obliteration of the arteriovenous shunt and for improving quality of life.

Long Term Outcome after Application of the Angio-Seal Vascular Closure Device in Minipigs

Minipigs are frequently used in (neuro-)interventional research. Longitudinal experiments may require repeated vessel access via the femoral artery. Anticoagulation and incompliance of the animals necessitates the use of a vascular closure device (VCD). The effects of the Angio-Seal VCD in minipigs were longitudinally assessed. Minipig (42±8.4 kg body weight) femoral arteries were sealed using the 8F (n = 6) or 6F (n = 7) Angio-Seal VCD. The pre-interventional femoral artery diameter was 5.1±0.4 mm (4.3–5.8 mm). Sealed puncture sites were analysed angiographically as well as by computed tomography angiography (CTA) for a mean period of 14.1±8.0 weeks (1–22 weeks). All animals were constantly treated with acetylsalicylic acid (ASS) (450 mg/d (n = 7) or 100 mg/d (n = 1)) and clopidogrel (75 mg/d (n = 8)). Non-instrumented (n = 2) and arteries sealed using the VCD (n = 2) were examined histologically. No postoperative hemorrhagic complications were observed. Three arteries were occluded after VCD placement (1 animal diagnosed after 4 weeks (8F), 2 animals after 1 week (6F)) and remained so until the end of the experiments after 22, 12 and 4 weeks, respectively. In one artery a 50% stenosis 8 weeks after application of a 6F Angio-Seal was detected. In 69.2% (n = 9) the VCD was applied without complications. Histopathological analysis of the sealed arterial segments showed subtotal obliteration of the vessel lumen, formation of collagenous tissue and partial damage of the internal elastic lamina. The Angio-Seal VCD prevents relevant hemorrhagic complications in minipigs treated with dual platelet inhibition, but is associated with increased vessel occlusion rates.

Abstract P238: Effect of Zamicastat in Chronic Treatment on Right Ventricle Pressure Overload in the Rat Monocrotaline Lung Injury Model of Pulmonary Hypertension

Pulmonary arterial hypertension (PAH) is defined, foremost, as a plexogenic arteriopathy with subtotal luminal obliteration that increases pulmonary vascular resistance and imposes a hemodynamic stress on the right ventricle (RV) leading to RV hypertrophy and failure that contributes to premature death. There is experimental and clinical evidence that supports a relation between PAH and the sympathetic nervous system (SNS), indicating that PAH can be mediated, at least partly, by SNS hyperactivation. A strategy for the modulation of sympathetic nerve function is to reduce the biosynthesis of norepinephrine (NE) by inhibiting dopamine β-hydroxylase (DβH), the enzyme that catalyzes the conversion of dopamine (DA) to NE in sympathetic nerves. Here, we evaluated the effect of 18-day oral treatment with the DβH inhibitor zamicastat on RV pressure overload in the monocrotaline (MCT)-induced pulmonary hypertension (PH) model in the rat. MCT increased RV systolic pressure (54.7±2.9 vs 32.3±1.0 mmHg, p&lt;0.0001), mean RV pressure (23.9±1.7 vs 16.6±1.1 mmHg, p&lt;0.001), and decreased heart rate (240.0±5.9 vs 285.8±7.6 beats/min, p&lt;0.0001) in vehicle-treated rats, as compared to pre-MCT values. Zamicastat treatment prevented the MCT-induced increase in mean RV pressure (change from baseline: +1.9±1.5 vs +7.4±1.8 mmHg, p&lt;0.05). Likewise, the HR decrease was significantly attenuated in the zamicastat group as compared to the vehicle group (change from baseline: -14.3±9.7 vs -45.8±8.1 beats/min, p&lt;0.05). Chronic zamicastat treatment decreased NE levels (480.5±43.9 vs 712.1±46.5 ng/mg protein, p&lt;0.005) and increased DA levels (533.0±49.7 vs 12.3±2.3 ng/mg protein, p&lt;0.0001) in adrenal gland homogenates of MCT-treated rats, as compared to vehicle group demonstrating robust inhibition of DβH. In conclusion, the DβH inhibitor zamicastat reverses heart rate and RV pressure changes, two hallmarks of PAH, in the rat MCT lung injury model.

Occlusion of Posterior Fossa Dural Sinuses in Vein of Galen Malformation.

Spontaneous or progressive occlusion of the posterior fossa dural sinuses is often observed in patients with vein of Galen malformation, which can affect the clinical course. The aim of this study was to examine the patency of the posterior fossa dural sinuses in patients with vein of Galen malformation and to analyze the clinical and angiographic course of this condition. We retrospectively reviewed 61 consecutive children with vein of Galen malformations. Clinical presentation, management, outcome, and angiographic change were analyzed for the patients with attention paid to all dural sinus occlusions. Twenty patients (32.8%) demonstrated spontaneous sinus occlusion, mostly in the sigmoid sinus. This condition was not observed in neonates and was first discovered during infancy or childhood. Progression of sinus occlusion was seen in 10 patients, and the conditions of 6 of them deteriorated in accordance with the progression of sinus occlusion. After total or subtotal obliteration of the malformation by transarterial glue embolization, 13 patients recovered to healthy, 3 patients had only mild developmental delay, and 4 patients remained neurologically disabled. Spontaneous sinus occlusion is not a rare condition and can result in neurologic deterioration in the natural history of untreated vein of Galen malformation. If signs of progressive sinus occlusion are noticed, early arteriovenous shunt reduction or elimination by transarterial glue embolization is expected to prevent permanent brain damage.

Epidemiologic Survey of Dural Arteriovenous Fistulas in Japan: Clinical Frequency and Present Status of Treatment.

There are few reports describing the prevalence of dural arteriovenous fistulas (dAVFs). We conducted a nation-wide retrograde survey on the clinical frequency and the status of treatment of dAVFs in Japan. The first questionnaire was sent to 1,236 certified neurosurgery clinics in Japan to ask about the number of patients treated and the location of dAVF during the 5 years from 1998 to 2002. The second questionnaire was sent to 102 large-volume centers to ask the patients' ages, gender, location of the fistula, clinical presentation, treatment modalities, clinical and radiological results, and recurrence. In the first survey, 1,815 cases were chosen from 338 clinics, including 826 cavernous sinus, 514 transverse-sigmoid sinus, 105 spinal, and 370 lesions in other places. The estimated detection rate was 0.29 per 100,000 persons per year in Japan. In the second survey, there were 1,490 cases (mean age: 62.7 ; 628 men and 850 women) that were culled from 68 high-volume centers. The initial clinical presentation was ocular symptoms (45 % of the cases), tinnitus (20 %), intracranial hemorrhage (16 %), and non-hemorrhagic neurological deficits (20 %). Treatment modality was endovascular therapy (76 % of the patients), open surgery (13 %), irradiation (3.4 %), and conservative therapy (11 %). Angiographic results were total obliteration in 59 % of the patients and subtotal obliteration in 16 %. Clinical symptoms disappeared in 54 % of the patients, improved in 16 %, unchanged in 7 %, worsened in 1.5 %, and death occurred in 1.2 %. Recurrence was reported in 5.9 % of the patients. This survey delineated the clinical frequency and the epidemiologic features of dAVF in Japan.

Embolization with Gamma Knife Radiosurgery of Giant Intracranial Arteriovenous Malformations.

Giant arteriovenous malformations (i.e., those greater than 6 cm maximum diameter or volume > 33 cc) are difficult to treat and often carry higher treatment morbidity and mortality rates. In our study, we reviewed the angiographic results and clinical outcomes for 11 patients with giant arteriovenous malformations who were treated between 1994 and 2012. The patients selected included 9 males (82%) and 2 females (18%). Their presenting symptoms were hemorrhage (n=2; 18%), seizure (n=7; 64%), and headache (n=2; 12%). Nine patients were Spetzler-Martin Grade III, 2 were Spetzler-Martin Grade IV. The mean arteriovenous malformation volume was 41 cc (33-52 cc). The mean age of the patients was 45.1 years (24-57 years) and the mean radiation dose delivered to the margin of the nidus was 14.2 Gy. Ten patients received pre-Gamma Knife radiosurgery embolization and Gamma Knife radiosurgery, 1 patient received pre-Gamma Knife radiosurgery embolization and Gamma Knife radiosurgery twice and the interval between Gamma Knife radiosurgeries was 3 months. The complete obliteration rate following Gamma Knife radiosurgery was 36%, subtotal obliteration ( > 70% decreased size of nidus) was 36%, and partial obliteration was 28%. One patient experienced a small hemorrhage after embolization. Combined embolization and Gamma Knife radiosurgery showed successful obliteration of the arteriovenous malformation nidus. The use of embolization to initially reduce nidus size followed by Gamma Knife radiosurgery improves the treatment results. Repeated Gamma Knife radiosurgery should be a treatment option when there is a small nidus remnant.

Remission of neurovascular conflicts in the cerebellopontine angle in interventional neuroradiology

Background and purposeTo investigate the efficacy of endovascular treatment (EVT) for neurovascular conflicts (NVCs) in the cerebellopontine angle (CPA) caused by intracranial aneurysms (IAs) and intracranial arteriovenous malformations (AVMs), including...

Large volumeやeloquent regionのAVMに対するサイバーナイフ少数回分割定位放射線治療

Single-fraction stereotactic radiosurgery (SRS) is effective for small volume arteriovenous malformations (AVMs). However, large AVMs, and AVMs in eloquent regions are often not cured with SRS, because we cannot give an adequate dose to the AVMs without causing radiation damage to the surrounding normal brain tissue. We have used hypo-fractionated stereotactic radiotherapy (HFSRT) including SRS with Cyberknife (CK) for these AVMs in eloquent regions or large volume AVMs. The aim of this study is to evaluate the effectiveness of our HFSRT including SRS with CK for these AVMs with possibly a lower complication rate. During the past six years, single-fraction SRS was used as a basic treatment method for AVMs located in non-eloquent regions or for small volume AVMs. We have treated 36 cases (17 males and 19 females) of large AVMs and AVMs in eloquent regions with HFSRT, including SRS using CK. The age ranged from seven to 66 years (average 33 years). A mean marginal dose of 27 Gy (range 16–30 Gy) was prescribed and the average isodose was 76% (range 64-86%) isodose. Most patients were treated with the HFSRT method (three to five fractions) except for six SRS cases. 3-D SPGR MRA was performed with a 3T MR scanner (Signa HDX 3.0T, GE, US). The time-dependent relative decay of the trans-nidal blood flow and sequential volumetric reduction evidenced by 3D SPGR MRA was referred to as “obliteration dynamics.” All patients had periodical follow-up studies at regular intervals. Subtotal obliteration was determined if the residual nidus volume was 5% or less of the initial nidus volume. The mean follow-up period was 37 months (6–53). All patients tolerated the procedures well. After the treatment, a significant obliteration dynamics was observed in all patients over a 12-month follow-up. Subtotal obliteration was obtained in 11 patients out of 18 (61%) who had over 24-month follow-up. In conjunction with the gradual reduction of AVM volume after CK treatment, visual field defects improved, motor functions recovered and easy medical control of symptomatic epilepsy was realized in a significant number of cases. HFSRT with CK was found to be safe and effective. The use of sequential 3D SPGR MRA at 3T enables a noninvasive quantitative assessment of the dynamic obliteration process induced by HFSRT with CK in AVMs. If the long term follow-up sustains these preliminary results, HFSRT with CK could become the first treatment of choice for large AVM and eloquent regions.

Gamma Knife surgery for basal ganglia and thalamic arteriovenous malformations

Gamma Knife surgery (GKS) has emerged as the treatment of choice for small- to medium-sized cerebral arteriovenous malformations (AVMs) in deep locations. The present study aims to investigate the outcomes of GKS for AVMs in the basal ganglia and thalamus. Between 1989 and 2007, 85 patients with AVMs in the basal ganglia and 97 in the thalamus underwent GKS and were followed up for more than 2 years. The nidus volumes ranged from 0.1 to 29.4 cm(3) (mean 3.4 cm(3)). The mean margin dose at the initial GKS was 21.3 Gy (range 10-28 Gy). Thirty-six patients underwent repeat GKS for residual AVMs at a median 4 years after initial GKS. The mean margin dose at repeat GKS was 21.1 Gy (range 7.5-27 Gy). Following a single GKS, total obliteration of the nidus was confirmed on angiograms in 91 patients (50%). In 12 patients (6.6%) a subtotal obliteration was achieved. No flow voids were observed on MR imaging in 14 patients (7.7%). Following single or repeat GKS, total obliteration was angiographically confirmed in 106 patients (58.2%) and subtotal obliteration in 8 patients (4.4%). No flow voids on MR imaging were observed in 18 patients (9.9%). The overall obliteration rates following one or multiple GKSs based on MR imaging or angiography was 68%. A small nidus volume, high margin dose, low number of isocenters, and no history of embolization were significantly associated with an increased rate of obliteration. Twenty-one patients experienced 25 episodes of hemorrhage in 850 risk-years following GKS, yielding an annual hemorrhage rate of 2.9%. Four patients died in this series: 2 due to complications of hemorrhage and 2 due to unrelated diseases. Permanent neurological deficits caused by radiation were noted in 9 patients (4.9%). Gamma Knife surgery offers a reasonable chance of obliterating basal ganglia and thalamic AVMs and does so with a low risk of complications. It is an optimal treatment option in patients for whom the anticipated risk of microsurgery is too high.

Gamma Knife surgery for arteriovenous malformations in children

The aim of this study was to evaluate the long-term imaging and clinical outcomes of intracranial arteriovenous malformations (AVMs) in children treated with Gamma Knife surgery (GKS). Between 1989 and 2007, 200 patients with AVMs who were 18 years of age or younger were treated at the University of Virginia Health System. Excluding 14 patients who had not reached 2-year follow-up, 186 patients comprised this study. Hemorrhage was the most common presenting symptom leading to the diagnosis of AVMs (71.5%). The mean nidus volume was 3.2 cm(3) at the time of GKS, and a mean prescription dose of 21.9 Gy was used. After initial GKS, 49.5% of patients achieved total angiographic obliteration. Forty-one patients whose AVM nidi remained patent underwent additional GKS. The obliteration rate increased to 58.6% after a second or multiple GKS. Subtotal obliteration was achieved in 9 patients (4.8%). Forty-nine patients (26.3%) still had a patent residual nidus. In 19 patients (10.2%), obliteration was confirmed on MR imaging only. Ten patients had 17 hemorrhages during the follow-up period. The hemorrhage rate was 5.4% within 2 years after GKS and 0.8% between 2 and 5 years. Six patients developed neurological deficits along with the radiation-induced changes. Two patients developed asymptomatic meningiomas 10 and 12 years after GKS. After a mean clinical follow-up of 98 months, less than 4% of patients had difficulty attending school or developing a career. Gamma Knife surgery offers a reasonable chance of obliteration of an AVM in pediatric patients. The incidence of symptomatic radiation-induced changes is relatively low; however, long-term clinical and imaging follow-up is required to identify delayed cyst formation and secondary tumors.

Repeat Gamma Knife Surgery for Incompletely Obliterated Cerebral Arteriovenous Malformations

The causes of failure after an initial Gamma procedure were studied, along with imaging and clinical outcomes, in a series of 140 patients with cerebral arteriovenous malformations (AVMs) treated with repeat Gamma Knife surgery (GKS). Causes of initial treatment failure included inaccurate nidus definition in 14 patients, failure to fill part of the nidus as a result of hemodynamic factors in 16, recanalization of embolized AVM compartments in 6, and suboptimal dose (<20 Gy) in 23. Nineteen patients had repeat GKS for subtotal obliteration of AVMs. In 62 patients, the AVM failed to obliterate despite correct target definition and adequate dose. At the time of retreatment, the nidus volume ranged from 0.1 to 6.9 cm3 (mean, 1.4 cm3), and the mean prescription dose was 20.3 Gy. Repeat GKS yielded a total angiographic obliteration in 77 patients (55%) and subtotal obliteration in 9 (6.4%). In 38 patients (27.1%), the AVMs remained patent, and in 16 patients (11.4%), no flow voids were observed on magnetic resonance imaging. Clinically, 126 patients improved or remained stable, and 14 experienced deterioration (8 resulting from a rebleed, 2 caused by persistent arteriovenous shunting, and 4 related to radiation-induced changes). By using repeat GKS, we achieved a 55% angiographic cure rate. Although radiation-induced changes as visualized on magnetic resonance imaging occurred in 48 patients (39%), only 4 patients (3.6%) developed permanent neurological deficits. These findings may be useful in deciding the management of AVMs in whom total obliteration after initial GKS was not achieved.

High-contrast computed tomographic angiography better detects residual intracranial arteriovenous malformations in long-term follow-up after radiotherapy than 1.5-tesla time-of-flight magnetic resonance angiography

Computed tomography angiography (CTA) and magnetic resonance angiography (MRA) are noninvasive alternatives for therapy monitoring of cerebral arteriovenous malformation (AVM). To evaluate if CTA is able to detect residual AVM in the long-term follow-up after radiotherapy when time-of-flight (TOF) MRA could no longer detect a remaining nidus. 18 patients with intracranial AVM were included between November 2005 and August 2007 who were scheduled for CTA (16-slice CT, 1-mm slice thickness, 90 ml iomeprol 400 mg I/ml, 4 ml/s) in the follow-up of radiotherapy. In these patients, MRA (3D-TOF, and bolus tagging at 1.5 T) could no longer detect a remaining nidus. The previously performed MRA (median time between CTA and MRA, 2.5 months) described total obliterations in 14 and subtotal obliterations in two AVM cases. Two MRA diagnoses were inconclusive due to artifacts. CTA (median time after therapy, 28 months; range, 5-66 months) could provide a diagnosis in all cases, but confirmed the MRA diagnosis only in 50% of the cases. A residual nidus was shown in an additional six cases, and subtotal obliteration in another three cases. The interval between radiotherapy and the follow-up examination was significantly different (P<0.05) between false- and true-negative MRA examinations (median, 18 vs. 30 months). High-contrast CTA is a sensitive tool in the detection of AVM and is able to identify residual AVM after radiotherapy even if previously performed TOF MRA at 1.5 T shows total obliteration.

THE PROTECTIVE STATUS OF SUBTOTAL OBLITERATION OF ARTERIOVENOUS MALFORMATIONS AFTER RADIOSURGERY

Arteriovenous malformations (AVMs) treated by radiosurgery with complete obliteration of the nidus but a persisting early draining vein on follow-up angiography can be termed subtotally obliterated. However, these are persistent circulating AVMs. The significance of these lesions, their hemorrhage rate, and their management are analyzed. In a series of 862 consecutive patients with AVMs treated by radiosurgery, 121 patients (14%) achieved subtotal obliteration (STO). The angiographic evolution and rate of obliteration were studied. The pretreatment angiographic features, dosimetric parameters, and postradiosurgery hemorrhage rate were compared with those in the rest of the treated population. Finally, the options for follow-up and treatment were analyzed. Of 121 subtotally obliterated AVMs, the bleeding rate was 0%; 53% of patients achieved complete obliteration. This occurred in 71% of those who had STO at 1 year. In the cases in which STO was detected at 2, 3, and 4 years, total obliteration eventually occurred in 43%, 28.5%, and 0%, respectively. Comparative analysis with AVMs in which a part of the nidus persisted showed a significant difference in the bleeding rate. Except for volume, no significant statistical difference in angiographic and dosimetric parameters was found between the STO group and the rest of the studied population with residual nidus. Six cases received further treatment, resulting in 2 cures and 2 treatment-related complications. Subtotally obliterated AVMs are different from other partially obliterated AVMs, with a 0% bleeding rate. Their complete obliteration is a function of delay of appearance on follow-up angiography. Invasive follow-up and further treatment of these AVMs do not seem warranted.

Supratentorial Brain AVM Embolization with Onyx-18 and Post-Embolization Management

Onyx is increasingly used in endovascular therapy of intracranial arteriovenous malformations (AVMs). However, the embolic effect and post-embolization management are still under discussion. We report our experience in the treatment of supratentorial brain arteriovenous malformations (SBAVMs) with Onyx and discuss post-embolic management. From June 2006 to July 2008, 20 patients with SBAVM were embolized with Onyx. There were 14 men and six women ranging from 14 to 64 years of age (mean 38.3 years). Initial symptoms included spontaneous hemorrhage (n=12), headaches (n=4), seizure (n=3) and incidentally disclosed after head trauma (n=1). After the endovascular procedure, all had subsequent treatment (follow-up angiogram, stereotactic radiosurgery or microsurgery) according to the obliteration degree. At angiography, seven patients (35%, 7/20) were completely obliterated (over 95% closure) after embolization while one suffered a small subarachnoid hemorrhage without permanent clinical sequelae. Four patients (20%, 4/20) were subtotally obliterated (over 80% closure), one patient who suffered severe cerebral edema after embolization underwent decompressive craniectomy, two patients had additional radiosurgery and one patient had follow-up angiogram. Nine patients (45%, 9/20) were partially obliterated (20-80% closure), five patients had additional surgery, two patients had additional radiosurgery and two patients had follow-up angiogram (one patient had intraventricular hemorrhage three months after embolization). Of all 20 AVMs, an average of 2.2 ml Onyx was used per patient and average volume reduction was 80% (range, 30%-99%). Onyx is suitable for embolization of SBAVMs because of its diffuse controllable properties. We suggest clinical follow-up after complete obliteration, additional radiosurgery or angiographic follow-up after subtotal obliteration and additional surgery after partially obliteration. More cases with long-term follow-up are needed to evaluate the long-term prognosis of our post-embolization management.

Symptomatic enlargement of an occluded giant carotido-ophthalmic aneurysm after endovascular treatment: the vasa vasorum theory

We describe a patient with a symptomatic left giant carotido-ophthalmic aneurysm who initially underwent coil embolization with subtotal obliteration. The patient's symptoms were initially stable, but 1 year later, she presented with a rapidly progressive contralateral visual deficit. Although angiogram showed a stable neck remnant, MR confirmed aneurysm growth and showed a new peripheral hematoma in the wall of the thrombosed aneurysm. Surgical exploration was undertaken, and even after trapping and intra-aneurysmal thrombectomy, constant bleeding was observed from the wall of the thrombosed aneurysm consistent with the vasa vasorum. Bleeding stopped after cauterization and partial resection of the aneurysm dome, and the aneurysm was clipped. The patient's recent visual deficit markedly improved, and the angiogram did not reveal any residue. Giant aneurysms may continue to grow due to a hypertrophic vasa vasorum and subadventitial hemorrhages. Surgery should be considered if complete thrombosis of the aneurysm does not alleviate patient's symptoms.

OBLITERATION DYNAMICS IN CEREBRAL ARTERIOVENOUS MALFORMATIONS AFTER CYBERKNIFE RADIOSURGERY

To investigate the time-dependent obliteration of cerebral arteriovenous malformations (cAVM) after CyberKnife radiosurgery (CKRS) (Accuray, Inc., Sunnyvale, CA) by means of sequential 3-T, 3-dimensional (3D), time-of-flight (TOF) magnetic resonance angiography (MRA), and volumetry of the arteriovenous malformation (AVM) nidus. In this prospective study, 3D TOF MRA was performed on 20 patients with cAVMs treated by single-fraction CKRS. Three-dimensional TOF MRA was performed on a 3-T, 32-channel magnetic resonance scanner (Magnetom TIM Trio; Siemens Medical Solutions, Erlangen, Germany) with isotropic voxel size at a spatial resolution of 0.6 x 0.6 x 0.6 mm3. The time-dependent relative decay of the transnidal blood flow evidenced by 3D TOF MRA was referred to as "obliteration dynamics." Volumetry of the nidus size was performed with OsiriX imaging software (OsiriX Foundation, Geneva, Switzerland). All patients had 3 to 4 follow-up examinations at 3- to 6-month intervals over a minimum follow-up period of 9 months. Subtotal obliteration was determined if the residual nidus volume was 5% or less of the initial nidus volume. Stata/IC software (Version 10.0; Stata Corp., College Station, TX) was used for statistical analysis and to identify potential factors of AVM obliteration. Regarding their clinical status, case history, and pretreatments, the participants of this study represent difficult-to-treat cAVM patients. The median nidus volume was 1.8 mL (range, 0.4-12.5 mL); the median minimum dose prescribed to the nidus was 22 Gy (range, 16-24 Gy) delivered to the 67% isodose line (range, 55-80%). CKRS was well tolerated, with complications in 2 patients. No further hemorrhages occurred after RS, except 1 small and clinically inapparent incident. The median follow-up period after RS was 25.0 months (range, 11.7-36.8 months). After RS, a statistically significant obliteration was observed in all patients. However, the obliteration dynamics of the cAVMs showed a pronounced variability, with 2 types of post-therapeutic behavior identified. cAVMs of Group A showed a faster reduction of transnidal blood flow than cAVMs in Group B. The median time to subtotal obliteration was 23.8 months for all patients, 11.6 months for patients in Group A, and 27.8 months for patients in Group B (P = 0.05). Logistic regression analysis revealed dose homogeneity and the circumscribed isodose to be the only variables (P < 0.01) associated with the obliteration dynamics in this study. The cumulative complete angiographic obliteration rate was 67% (95% confidence interval, 32-95%) 2 years after RS. The use of sequential 3D TOF MRA at 3 T and nidus volumetry enables a noninvasive quantitative assessment of the dynamic obliteration process induced by CKRS in cAVMs. This method may be helpful to identify factors related to AVM obliteration after RS when larger patient cohorts become available.