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|NI FEATURE: THE QUEST - COMMENTARY
|Year : 2017 | Volume
| Issue : 6 | Page : 1355-1357
Options for the management of brain arteriovenous malformations
Rohen Harrichandparsad, DD Royston, SS Nadvi
Department of Neurosurgery, University of KwaZulu-Natal, Nelson R. Mandela School of Medicine, Inkosi Albert Luthuli Central Hospital, Durban, South Africa
|Date of Web Publication||10-Nov-2017|
Dr. Rohen Harrichandparsad
Department of Neurosurgery, Inkosi Albert Luthuli Central Hospital, Durban
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Harrichandparsad R, Royston D D, Nadvi S S. Options for the management of brain arteriovenous malformations. Neurol India 2017;65:1355-7
Brain arteriovenous malformations (AVMs) are challenging to manage. Management has to be individualised based on the age, clinical presentation of the patient and neuroimaging findings including angioarchitectural features.
The ultimate goal of treatment is to improve the natural history for the patient while minimizing the treatment risk.
After the publication of ARUBA (A Randomized trial of Unruptured Brain Arteriovenous Malformations), both surgical and endovascular interventions for unruptured brain AVMs have been questioned. ARUBA has been criticized for selection bias: 1740 patients were screened and 726 patients were eligible. 326 patients refused enrollment. Only 226 were randomized. The other 177 patients were managed outside of the randomization process. There were 66 centres listed, but only 39 enrolled patients. 14 centres enrolled only 1 or 2 patients. There was a lack of participation of large AVM centres. AVMs with low risk features were enrolled while high-risk AVMs were offered intervention. There was no rigorous physician accreditation in treatment outcome. Only 5 patients were allocated to microsurgery alone. The heterogeneity of patients and lack of standardization in the treatment arm, the low enrollment rate, selection bias and lack of long term follow up limits the conclusions one can draw from ARUBA.
It is true that brain AVM therapies carry substantial risk and not every patient with a brain AVM warrants intervention. On the other hand, there is a high lifetime cumulative risk of haemorrhage and observational therapy may not be applicable in every unruptured AVM.
In our practice, we have three options for intervention, which are used alone or in combination: surgery, endovascular therapy and stereotactic radiosurgery (SRS). When considering microsurgical excision of an AVM, the aim is always cure. Similarly, when considering an AVM for SRS, the aim is cure. The role of endovascular therapy for the management of AVMs in our practice is cure if possible; for partial targeted therapy; and, as part of multimodality management where embolisation is performed either before surgery or SRS.
AVMs suitable for cure by endovascular means are small AVMS with few feeding arteries and no en-passage vessels. Liquid embolic material is used to occlude the distal artery, nidus and proximal vein [Figure 1].
|Figure 1: A 33-year old male patient presented with a spontaneous posterior fossa hemorrhage. The CT angiogram shows a nidus of vessels in the vermis (a). The left vertebral injection shows the arterial supply via the distal superior cerebellar arteries (b). Selective injection of the superior cerebellar arteries show the nidus of vessels with deep venous drainage via the superior vermian vein into the straight sinus (c). The AVM was embolised with a liquid embolic agent and control run shows complete obliteration of the nidus (d). The patient made a full clinical recovery with no neurological deficits|
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In patients who present with a progressive neurologic deficit, the angioarchitecture is studied to identify possible targets based on the angioclinical semiology. This partial targeted therapy is used to ameliorate the patient's symptoms [Figure 2]. Similarly, if the angiogram shows high risk features like high flow fistulae or if a rupture point (e.g., intranidal aneurysm) can be identified, these are targets for embolisation [Figure 3]. By targeting these high-risk angiographic weak points, we are able to reduce the bleeding risk of the patient thus improving the natural history.
|Figure 2: An 18-year old male patient presented with progressive quadriparesis. MRI of the cervical spine shows abnormal flow voids around the spinal cord (a). MRI brain showed a left thalamic AVM. Digital subtraction angiogram showed the AVM supplied by multiple feeders with both superficial and deep venous drainage. Closer examination of the right internal carotid run shows the deep venous drainage communicating with the spinal venous system via the lateral mesencephalic vein (b). Selective injection of the feeding artery clearly shows the spinal venous congestion (c) which correlates with the MRI and the patient's clinical presentation. Partial targeted embolization to disconnect this communication was achieved with liquid embolic agents. Control right internal carotid artery run shows the AVM still filling but with no drainage into the spinal venous system (d). Postoperative MRI prior to discharge shows the resolution of the spinal venous congestion and no flow voids (e). This was accompanied by a dramatic clinical recovery over the next few weeks|
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|Figure 3: A 27-year old male patient presents with a spontaneous left basal ganglia intracerebral hemorrhage with intraventricular hemorrhage, as depicted on MRI (a). Digital subtraction angiogram of the left internal carotid artery shows a nidus of vessels (b). Selective angiogram of the left lenticulostriate feeder shows the pseudoaneurysm which is the rupture point (c). This was embolized with a liquid embolic agent and control angiogram shows a residual AVM but no filling of the aneurysm (d)|
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Finally, we advocate multimodality management of selected AVMs where endovascular therapy is used as an adjunct either before surgery or SRS.
Pre-surgical embolisation offers potential benefits by targeting the deep part of the nidus, which may be more difficult to access during surgery since it is typically encountered during the latter stages of AVM dissection. Pre-radiotherapy embolisation is used to decrease the size of a large AVM nidus making it amenable to SRS.
AVMs that have bled require treatment because there is a significantly higher risk of rebleeding. AVMs that have not bled have to be further analysed to carefully select those patients in whom treatment may be beneficial. An assessment of the clinical presentation together with the angioarchitecture on digital subtraction angiography identifies those patients with high-risk features for further haemorrhage. Treatment is indicated in these patients if the treatment risk is lower than the anticipated risk based on the natural history of the AVM.
For the majority of low-grade AVMs, which are amenable to cure, surgery remains the “gold standard”. The use of technology to facilitate safer surgery has been evident through the decades with the advent of the operating microscope and microneurosurgical techniques coupled with advances in neuroimaging. Microscope-integrated indocyanine green (ICG) has been used in AVM surgery to help differentiate AVM vessels from normal vessels and arteries from veins. Similarly, the use of intraoperative three-dimensional ultrasound and navigation has been used to adapt resection strategies and help define dissection planes. Shah et al., report in this issue on their novel use of three-dimensional printed models as a pre-operative investigational modality. One of the advantages of this technique is that it offers patient-specific precise identification of the AVM location, which is useful to plan the craniotomy. It also helps to improve surgeon comfort and confidence during the procedure by providing a physical three-dimensional (3-D) model of the anatomy, which can aid dissection. This technique also has applications in teaching and training of young neurosurgeons. Future developments should explore the use of 3D rotational angiography fusion with the CT angiogram to precisely identify feeding arteries, nidus and draining veins. These can be colour coded accordingly and is likely to add another dimension in understanding these complex lesions.
Management of brain AVMs is challenging and a number of factors have to be considered when planning optimal treatment. Management is individualised and patients are best treated in high volume centres where all modalities: microsurgery, endovascular therapy and stereotactic radiosurgery are available. All available adjuncts should be used to maximize treatment outcomes while minimizing treatment risks.
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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[Figure 1], [Figure 2], [Figure 3]