|Year : 2020 | Volume
| Issue : 6 | Page : 1293--1294
Endovascular Treatment in AVM Management: Towards Realistic Goals?
Ullas V Acharya1, Paritosh Pandey2,
1 Department of Neurointervention, Manipal Hospitals, Old Airport Road, Bangalore, Karnataka, India
2 Department of Neurosurgery, Manipal Hospitals, Old Airport Road, Bangalore, Karnataka, India
Dr. Paritosh Pandey
Department of Neurosurgery, Manipal Hospitals, Bangalore, Karnataka - 560017
|How to cite this article:|
Acharya UV, Pandey P. Endovascular Treatment in AVM Management: Towards Realistic Goals?.Neurol India 2020;68:1293-1294
|How to cite this URL:|
Acharya UV, Pandey P. Endovascular Treatment in AVM Management: Towards Realistic Goals?. Neurol India [serial online] 2020 [cited 2021 Mar 2 ];68:1293-1294
Available from: https://www.neurologyindia.com/text.asp?2020/68/6/1293/304073
Arteriovenous malformations (AVMs) are complex vascular lesions with multifactorial pathogenesis and multimodality treatment. The present review, analyses role of endovascular treatment either as stand alone or as surgical or radiosurgical adjuncts.
For an unruptured AVM, annual risk of bleed is around 2-4% which increases to approx 7% in the first year after hemorrhage in a ruptured AVM before dropping down to baseline after 3-5 years. Smaller size and deeper location of nidus, single draining vein, deep venous drainage, aneurysms, stenosis, occlusion in veins have been suggested as being correlated with risk of hemorrhage.
Endovascular management of AVMs are a subject of much debate. Despite the good results with microsurgery and radiosurgery in Spetzler-Martin grade 1-3 AVMs, there has been renewed enthusiasm for endovascular management of AVMs. There have been many advances in the understanding angio-architecture and flow in the AVMs, imaging, catheter technology, liquid embolics and other technology. However, as is shown in this review, there has not been a commensurate improvement in the clinical results. For endovascular treatment to be in the driver's seat in the treatment of AVMs, the results need to be similar to, or superior to the competing treatments of microsurgery and radiosurgery.
The main goal of brain AVM treatment is always to completely exclude it from circulation, thus preventing any future hemorrhage (even if AVM is large and multimodality treatment is planned) while minimizing treatment-related morbidity.
Indication for treatment appears beyond scope of this review article as no information on Spetzler Martin grade and hemorrhage status of AVMs prior to treatment is known. Indication to treat AVMs that have already ruptured is, in general, uncontroversial and clear. The treatment of unruptured AVMs (uAVM) is currently much more controversial. After extended follow-up (mean follow up of 50.4 months), ARUBA showed that medical management alone remained superior to interventional therapy for the prevention of death or symptomatic stroke in patients with an unruptured brain arteriovenous malformation (3·39 per 100 patient-years as compared to 12·32 per 100 patient-years respectively). However such generalization for a disease with lifelong hemorrhagic risk, and of different nature along with multimodal treatment options needs caution. More aggressive treatment attitude may be necessary in a younger patients, since the cumulative natural history risk during the remaining lifetime is higher and the potential for recovery from possible complications better. A 'one size fits all' policy is undesirable and in the current era, uAVMs need to be managed on a case-by-case basis especially in a cohort of Spetzler Martin grade III patients as rate of complications and natural history differs. Pandey et al. reported a surgical morbidity of 4.8% in SM Grade IIIa, 14.4% in SM Grade IIIb, 15.7% in SM Grade IIIc, and 28.6% in SM Grade IIId BAVMs.
Endovascular treatment is used in two ways, as a potentially curative treatment, and as an adjunct to either surgery or radiosurgery. For most AVMs via trans arterial route, select feeding arteries that allow microcatheter access as close to the nidus as possible. NBCA (N butyl CyanoAcrylate) mixture can be tailored depending on the arteriovenous shunting. Most common mixture ratios of NBCA to Ethiodol are 1:3 or 1:2. Denser mixtures can be used if there is a fistulous component with fast flow into the veins. More diluted mixtures can penetrate better into the nidus with the drawback of higher chance of reflux. Another technique to improve the NBCA penetration into the lesion is flushing the guiding catheter continuously with D5 dextrose solution while injecting the glue. In addition, beat-to-beat blood pressure monitoring is valuable if induced hypotension and reduced flow in the feeding artery of an intracranial AVM are required during glue injection. The major advantage of Onyx (ethylene vinyl alcohol copolymer) and like is the non-adhesive nature, which allows longer injection time, with the ability to perform control angiography when needed. Onyx laminates along the venous wall without immediate occlusion of the vessel. Recent trends in embolization techniques include creation of wedge-like position either with use of dimethyl sulfoxide compatible dual lumen balloon microcatheters or with a plug composed of coils and glue using pressure cooker technique (PCT) to increase the penetration of liquid embolic with minimal or no reflux. Better navigability of flow-directed microcatheters and avoidance of risk of vessel perforation during balloon inflation are advantages of PCT.
In situations in which arterial access is not feasible, successful transvenous embolization has been reported. Theoretical criteria to select cases include small lesions with a nidus of <2 cm, hemorrhagic AVMs, patients who are not good surgical candidates, arterial feeders that are not amenable to transarterial embolization like en passage feeders, lenticulostriate arteries or choroidal arteries, and AVMs preferably with a single drainage vein. It has theoretical advantages of better penetration of the AVM nidus, less risk of ischemic events due to arterial occlusion, and relatively easier navigation through enlarged and usually straighter veins. Though significantly high complete obliteration rates between 80% and 100% has been reported, number of sample cases has been small. Arterial flow arrest with transient balloon occlusion or simultaneous transarterial embolization should be used if technically feasible along with systemic hypotension during and after embolization. Nonadhesive EVOH should be used for transvenous embolization. However, the target venous structures must be accessibe and not be required for normal brain veins. Blocking veins of a true arteriovenous malformation prior to occluding the arterial feeders and nidus is a recipe for disaster with a high risk of bleed. It is to be seen whether this technique will be useful in a large group of AVMs, or will be reserved for a very small subset of AVMs.
In the present review, the low cure rates and high complication rates of EVT in AVMs is highlighted. Across 30 studies, involving 5103 patients, cure was obtained in only 18% patients. Where the intent was there for cure in monotherapy, the cure rate was 24%. Though Onyx increased the cure rates, it also led to higher hemorrhagic complications. The cure rate for pre-surgical and pre-radiosurgical embolization was lower at 10% and 16%. These results are significantly worse than most of the surgical and radiosurgical series, both in terms of cure rate and complications. This raises an important question about the role of EVT in AVM management, particularly in Grade 1–3 AVMs, where the other two modalities give much better results.
This review is a timely reminder of the limitations of EVT in AVM management, and the need for very careful evaluation of each AVM for suitability of different treatment methods. Based on the lower cure rate and higher complications of EVT, it would be fair to say that other modalities should be preferred over EVT, if feasible. It remains to be seen whether newer techniques in EVT will make the therapy more effective and safer.
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Conflicts of interest
There are no conflicts of interest.
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