A total of 63 participants from 49 (73.1%) institutions responded to our questionnaire (Figure 1). 38 participants (60.3%) were department directors, and 62 participants (98.4%) have more than 5 years of experience in the clinical treatment of bAVMs. Of the 63 participants, 42 (66.7%) were neurosurgeons, 13 (20.6%) were neurointerventionists, 8 (12.7%) were radiosurgeons. Approximately 3500 to 4000 cases of bAVMs were treated annually in these 49 departments.
General Questions
Microsurgery, Embolization, Radiosurgery (63 participants)
- Did you agree with the conclusions of ARUBA that conservative management is better than intervention for unruptured bAVMs and could these conclusions be generalized to all unruptured bAVMs (single-choice question)?
All participants (100.0%) agree that the conclusions of ARUBA are debatable and cannot be generalized to all unruptured bAVMs.
- What do you think are the risk factors for subsequent hemorrhage in unruptured bAVMs (multichoice question)?
Flow-related aneurysms (60 participants, 95.2%), deep venous drainage (47 participants, 74.6%), arteriovenous fistula (AVF) (43 participants, 68.3%), periventricular location (26 participants, 41.3%), and small nidus (26 participants, 41.3%) were considered as risk factors for subsequent hemorrhage of unruptured bAVMs (Figure 2). There was no difference of opinion among the three departments (P>0.05).
- Do you think unruptured Spetzler-Martin (SM) grade IV-V bAVMs are the interventional contraindications (single-choice question)? If not, which kind of unruptured SM IV-V bAVMs should take intervention management (multichoice and open question)?
The majority of participants (44 participants, 69.8%) suggested intervention for specific SM grade IV-V unruptured bAVMs, especially in patients with high hemorrhagic predictors (Figure 3A). There was no difference of opinion among the three departments (P=0.942). Besides, younger bAVMs (41 participants, 65.1%) were also recommended positive intervention because of the high cumulative subsequent rupture risk.
- Do you think giant bAVMs (>6cm) are the contraindication of intervention (single-choice question)? If not, which kind of intervention modality do you recommend (multichoice question)?
55 participants (87.3%) thought giant bAVMs were not interventional contraindications, and multi-modality intervention strategy was recommended by 40 participants (72.7%) (Figure 3B). But the multi-modality combinations were different within three departments, combined embolization and microsurgery (61.1%) was the most preferred strategy of the neurosurgeons, and combined embolization and radiosurgery (66.7%) was more preferred by the radiosurgeons. However, target embolization (58.3%), including embolization of cerebral aneurysms and high-flow AVFs, was the most preferred intervention strategy for giant bAVMs among neurointerventionists.
- Do you think pediatric bAVMs are the contraindication of intervention (single-choice question)? Do you think pediatric intervention strategies should be more aggressive than adults (single-choice question)? And which kind of intervention modality do you recommend for pediatric bAVMs (multichoice question)? Do you agree that the purpose of intervention in pediatric bAVMs is complete nidus obliteration and maximum functional protection (single-choice question)?
No participants (0.0%) agreed pediatric bAVMs were interventional contraindication. 46 participants (73.0%) thought the pediatric bAVMs should undergo more aggressive management than adults, and 37 participants (58.7%) recommended multi-modality intervention strategies for pediatric bAVMs (Figure 3C). There was no difference of opinion among the three departments (P=0.055). 57 participants (90.5%) agree that the purpose of intervention in pediatric bAVMs is complete nidus obliteration and maximum functional protection.
- Do you think elderly bAVMs (>65 years) are the contraindication of intervention (single-choice question)? If no, which kind of intervention modality do you recommend (multichoice question)? Do you recognize that partial occlusion and target embolization concentrated on hemorrhagic risk factors were more recommended than complete obliteration for elderly bAVMs (single-choice question)?
51 participants (81.0%) thought elderly bAVMs still need interventions. However, unlike adult patients, multi-modality strategies (36 participants, 70.6%) such as combined embolization and microsurgery (10 participants, 19.6%) or combined embolization and radiosurgery (26 participants, 51.0%) were more preferred than single modalities (15 participants, 29.4%) (P<0.01, Figure 3D). Besides, unlike pediatric patients, partial occlusion and target embolization (23 participants, 45.1%) concentrated on hemorrhagic risk factors were also recommended, rather than complete obliteration.
- Do you think eloquent AVMs are the contraindication of intervention (single-choice question)? Which intervention modality do you prefer (multichoice question)?
Most of the participants (51 participants, 81.0%) agreed that eloquent AVMs are decisive in their decision on treatment, but the interventional indications need to be personalized. 33 neurosurgeons (78.6%) proposed that only specific selected eloquent bAVMs would be recommended for microsurgical resection. 10 neurointerventionists (76.9%) consider that target embolization on the hemorrhagic risk factors was more preferred for bAVMs located in the eloquence area. All radiosurgeons (100.0%) believe that the Gamma knife has unique advantages for eloquent bAVMs, especially in small to moderate-sized and compact nidus (Figure 4A).
- What treatment strategy would you prefer for bAVMs with/without hemorrhagic risk factors located in the internal capsule, basal ganglia, thalamus and brainstem (multichoice and open question)?
For bAVMs with hemorrhagic risk factors, Most of the participants (59 participants, 93.7%) agreed with intervention treatment, and combined embolization and radiosurgery (65.1%) was the first-line recommended strategy. Besides, target embolization was suggested by 16 participants (25.4%) (Figure 4B). 14 neurosurgeons (33.3%) consider surgical resection as an alternative, especially for bAVMs with emergency hemorrhage.
For bAVMs without hemorrhagic risk factors, about half of the neurosurgeons (22 participants, 52.4%) preferred conservative management, but the majority of neurointerventionists (84.6%) and radiosurgeons (100.0%) suggested intervention treatment. Among the 39 participants who supported the intervention, 27 participants (69.2%) recommended radiosurgery (41.0%) or combined embolization and radiosurgery (28.2%) (Figure 4C).
- When do you think is the best intervention timing in patients with stable ruptured bAVMs (vital signs are stable, no obvious signs of cerebral hernia) (single-choice question)? Acute phase (within 48 hours)/ Subacute phase (7 days to 1 month)/ Chronic phase (1 month to 3 months)/ Recovery phase (> 3months)
There were significant differences in the timing of intervention among the three departments (P<0.01). Most neurosurgeons (90.5%) and neurointerventionists (92.3%) didn’t recommend intervention in the chronic phase or recovery phase. In the subgroup of neurosurgeons, 12 participants (28.6%) recommended surgery during the acute phase, and 26 participants (61.9%) preferred the subacute phase. However, considered the high subsequent hemorrhagic risk and the advantages of target embolization on hemorrhagic risk factors, 6 of neurointerventionists (46.2%) suggested embolization during the acute phase. Unlike either, the majority of radiosurgeons (87.5%) suggested intervention in the chronic phase or recovery phase, and preferably 3 months after bleeding (Figure 5).
Subgroup Detail Questions
Microsurgery, Embolization (55 participants)
- Do you think that the single-stage combined embolization and microsurgery strategy is beneficial (single-choice question)? If yes, which of the following is the most important (single-choice question)? Intraoperative angiography (clarify angioarchitecture characteristics and avoid lesion residue) / Intraoperative embolization. If you select intraoperative embolization, which embolization strategy do you prefer (multichoice and open question)?
All 55 neurosurgeons and neurointerventionist (100.0%) agreed that single-stage combined embolization and microsurgery is beneficial. Most of them (60.0%; 24 neurosurgeons, 57.1%; 9 neurointerventionists, 69.2%) considered intraoperative embolization as the most significant advantage because of the reduced flow and volume of the nidus. Besides, intraoperative target embolization for the hemorrhagic predictors (69.1%) and the deep part of the nidus (58.2%) were the most recommended intraoperative embolization strategies. Only 29.1% of the participants suggested excessive embolization.
- Which of the following areas do you prefer to embolize in the single-stage combined embolization and microsurgery (single-choice question)? The feeding arteries / The feeding arteries and nidu And what’s the reason of your choice (open question)?
Different departments have different views on this question. 28 neurosurgeons (66.7%) believed that embolization of the feeding artery was the most advantageous intraoperative embolization strategy because of the reduced blood supply, and the embolization of the nidus should be avoided, especially in deep lesions, because the lesions after embolization would become hard and difficult to be exposed intraoperatively. However, most of the neurointerventionists (8 of 13 participants, 61.5%) believed embolization of the feeding artery and nidus is more beneficial because it can reduce the nidus volume and reduce the intraoperative blood loss.
Embolization (13 participants)
- What is the embolic material routinely used for bAVMs in your department (single-choice question)? And which embolization strategy do you think is more beneficial (single-choice question)? Embolize hemorrhagic risk factors/ Embolize hemorrhagic risk factors and the nidus
All participants (100.0%) preferred Onyx (eV3, Inc.) as their first choice when embolizing bAVMs. Most of the participants (12 participants, 92.3%) preferred to embolize hemorrhagic risk factors and nidus.
Radiosurgery (8 participants)
- What is the minimum margin dose you suggested for single-stage radiosurgery (open question)?
5 participants (62.5%) suggested 16 Gy as the minimum margin dose for single-stage radiosurgery, while 3 participants (37.5%) suggested 18 Gy.
- Do you agree that pre-radiosurgery embolization is not conducive to the subsequent obliteration after radiosurgery (single-choice question)? Which kind of bAVMs do you think would benefit from pre-radiosurgery embolization (multichoice and open question)?
All participants (100.0%) consider the pre-radiosurgery embolization might reduce the obliteration rate. However, they still recommended pre-radiosurgery embolization for specific selected bAVMs, such as patients with hemorrhagic risk factors (87.5%), high flow (37.5%) and large-volume nidus (62.5%).