Multiplug flow control technique as a novel transarterial curative approach for the endovascular treatment of cerebrovascular malformations

Abstract

Herein, we describe the use of a novel multiplug flow control technique for the curative transarterial embolisation of cerebrovascular malformations using liquid embolic agents (LEAs). The idea behind the use of this technique is to substantially control or arrest flow during LEA injection, with multiple plugs simultaneously formed from microcatheters that are placed within all or multiple feeders, so that the penetration of LEAs is facilitated, with flow control decreasing the washout of a malformation. This technique enables the complete occlusion of a vascular malformation in a shorter injection time than that in other methods because penetration is achieved faster. Details of this technique have been described in the treatment of two cases: one case of unruptured temporal arteriovenous malformation and in the other with a falcotentorial dural arteriovenous fistula, in which the vascular malformations were successfully occluded with transarterial embolisation.

Background

Cekirge et al ¹ described the use of a ‘prolonged repetitive reflux and push’’ technique with Onyx (Medtronic, California, USA), for a treatment with an aim that was radical as that of the microsurgical removal of a brain arteriovenous malformation (AVM).^2–4 Since then, additional techniques for the facilitation of reflux plug formation for early distal penetration have been described, such as a ‘pressure-cooker technique’’, intermittent balloon-inflation technique, dual lumen balloon catheter (DLBC) assisted injection technique and so on.^5–7

Herein, we describe the use of a ‘multiplug flow control technique’ for the purpose of curing vascular malformations where all feeders or a majority of feeders are catheterised with detachable tip microcatheters (DTMs) and DLBCs, first, to form plugs that arrest or substantially decrease the flow of a malformation and thereafter to proceed with simultaneous flow-arrested/flow-controlled injections until complete occlusion is achieved.

Case presentation

Case 1: brain AVM

A young patient had an unruptured, Spetzler-Martin Grade 3 right temporal AVM. Angiography with four-dimensional (4D) evaluation revealed multiple intranidal aneurysms, three prominent feeders from the right middle cerebral artery (MCA) and another from the posterior temporal branch of the right posterior cerebral artery (PCA) were observed, with no dural supply and apparent deep drainage (figure 1, online supplemental video 1).

Figure 1.

Transarterial multiplug curative embolisation of Spetzler-Martin Grade 3 right temporal AVM: (A) right ICA angiography, lateral view; (B) left vertebral angiography, lateral view; (C) after placement of three Apollo DTMs (white arrows) and one 6×7 mm Eclipse 2L DLBC (black arrow) for multiplug flow control technique; (D) intranidal Onyx cast formed after simultaneous multiplug injections; (E) lateral view, late arterial and venous phase of postoperative simultaneous right carotid and left vertebral angiography revealing emboclosure of the AVM. (F) Postoperative diffusion MRI. AVM, arteriovenous malformation; DTMs, detachable tip microcatheters; ICA, internal carotid artery.

Case 2: dural arteriovenous fistula (AVF)

The patient presented with headache, tinnitus, ataxia and symptoms of dementia and had a falcotentorial dural AVF that was fed by the bilateral middle meningeal arteries (MMAs), right posterior meningeal artery, artery of Davidoff and Schechter of the left PCA (with a distal flow-related aneurysm), bilateral meningohypophyseal trunks of the internal carotid artery and pericallosal arteries of the bilateral anterior cerebral arteries. All shunts were draining into the vein of Galen and straight sinus, which were not used in the normal brain drainage (figure 2, online supplemental video 2).

Figure 2.

Transarterial multiplug curative embolisation of the falcotentorial dural AVF: (A) Right ICA angiography, lateral view; (B) Left ICA angiography, lateral view; (C) Right External Carotid Artery (ECA) angiography, lateral view; (D) Left ECA angiography, lateral view; (E) right vertebral angiography, lateral view; (F) Antero-Posterior (A-P) view: two Scepter XC DLBCs in bilateral middle meningeal arteries (black arrows) and one Apollo DTM in the right posterior meningeal artery (white arrow) and another in the left artery of Davidoff and Schechter (white arrowhead); (G) A-P and lateral views, postoperative simultaneous bilateral carotid and right vertebral angiography showing complete occlusion of the dural AVF. AVF, arteriovenous fistula; DTM, detachable tip microcatheter.

Treatment

Case 1: flow control was strategised and carried out by placing three Apollo DTMs in all the MCA feeders (Medtronic California, USA) and an Eclipse 2L DLBC (Balt, Montmorency, France) in the posterior temporal artery for near flow arrest. Thereafter, simultaneous Onyx 18 (Medtronic California, USA) injections were initiated; once multiple plugs had been formed with Onyx reflux at the tips of the DTMs and at that of the inflated balloon, Onyx injections were continued until the closure of the AVM nidus and feet of the draining veins, which was monitored by intraoperative, simultaneous carotid and vertebral control angiography, was achieved.

Case 2: in this case, the strategy was to achieve near-complete flow control, ignoring the relatively less flow supplies of the shunts from the bilateral cavernous ICA branches and pericallosal arteries. Two Scepter XC DLBCs (MicroVention, California, USA) were placed in the bilateral MMAs, and two Apollo DTMs were placed in the right posterior meningeal artery and left artery of Davidoff and Schechter, close to the shunt sites. Injections were administered from the artery of Davidoff and Schechter and posterior meningeal artery, because this would serve to decrease the washout of the LEAs with flow control and because this would prevent the possibility of further proximal occlusion of these arteries due to an untoward retrograde reflux from a shunt site during embolisation. To obtain this access, three 6 Fr long introducer sheaths (DuraSheath, CMI, Germany) were placed in the right vertebral artery and bilateral common carotid arteries via the right radial and bilateral femoral arteries, respectively. Multiplug flow-controlled Onyx 18 and Phil 25% (MicroVention) injections were simultaneously administered via the DLBCs and DTMs until closure of the dural malformation, as monitored by intraoperative, simultaneous bilateral carotid and vertebral artery control angiography, was achieved.

Outcome and follow-up

Case 1: the patient had an uneventful postoperative period and was neurologically intact when discharged. Control angiography at 6 months confirmed the persistent closure of the malformation.

Case 2: the patient left the hospital after an uneventful postoperative course, and he will have a control Digital Subtraction Angiography (DSA) at 1 year.

Discussion

Previously described techniques in the embolisation of cerebral vascular malformations aimed at an improved distal penetration of LEAs and increased effectivity with an improved control of the flow from a single pedicle.^{1 5–7} The double catheter injection technique has been described in a few previous publications,^{8 9} where the intent of the treatment was either to provide a cure only if an AVM was small or if an AVM had already reduced in size or to decrease the number of treatment sessions for large AVMs. However, even if there is good flow control in one pedicle or in a maximum of two pedicles, the other feeders of a malformation may wash out LEA through a nidus or fistula point, which leads to an unwanted early venous escape of the LEA, with ineffective nidal or fistula point penetration. Instead, the multiplug flow control technique¹⁰ aims to arrest or control the flow of malformations as much as possible. This allows for a closed system to be maintained, and LEA can then be directed exclusively into the nidus or around dural shunts; therefore, the untoward escape of LEA due to washout flow from uncontrolled pedicles can be limited or totally avoided. This technique minimises venous leakage and minimises the length of reflux plugs over DTMs because forward penetration starts immediately or very early due to a closed, flow-controlled system with a relatively short length of reflux on the tips of DTMs. Therefore, this may result in a substantial decrease in the total amount of LEA used for the exclusive occlusion of a nidus and the feet of draining veins close to the nidus; this result could represent an ideal curative emboclosure.

The occlusion of a malformation via shorter reflux plugs in its feeders and through the occlusion of its draining veins, just at their feet out of a nidus, without distal embolisation, may be advantageous for decreasing the risk of the occurrence of arterial and venous ischaemic and haemorrhagic complications.

The application of this technique definitely requires the use of a biplane angiography system, and in the present cases, 4D angiography was extremely useful for understanding the anatomy and morphology of the malformations and for strategising the treatment. A disadvantage of this technique could be that two or more accesses are required to place several microcatheters; this certainly takes time, and each microcatheterisation step may have its own inherent risks. However, once injection is begun, time is saved due to the obvious acceleration during LEA penetration.

The most difficult aspect of the technique could be the challenge in monitoring multiple microcatheters during injection. It is essential to define two working projections showing the longer courses of all DTMs that are differentiated from one another at least on one plane. Furthermore, during the embolisation process, changing the fluoroscopic viewing angle may be necessitated to avoid cast superimposition over the more proximal catheter segment where further reflux is to occur; the proximal marker of the detachable segment is the ultimate point of interest, and its visibility must be secured. Using different types of LEAs together may ease the differentiation of the penetration territory for different microcatheters based on their respective radiodensities. Still, at least two operators are needed to control more than two injections at a time while performing this technique. Another tip is that to match an emerging LEA with a particular microcatheter, operators can start administering injections consecutively after the renewal of each roadmap.

The technique described is complex and requires a high-end angiography machine and a team approach, with preferably at least two operators who have a clear understanding of vascular malformations and experience in their management. For the wide adoption of this technique, its safety and efficacy must first be evaluated in a large-scale case series.

Learning points.

• The novel ‘multiplug flow control’ technique is described for the curative transarterial embolisation of cerebrovascular malformations.

• Liquid embolic agent (LEA) injections are made from multiple microcatheters and double lumen balloon catheters placed within all or multiple major feeders simultaneously.

• The flow control decreases the washout of the malformation and facilitate the LEA penetration. Complete occlusion is achieved faster.

• Possible limitations: requirement of multiple accesses and more than one operator for simultaneous injection.