Transvenous embolization of vein of galen aneurysmal malformations using the “Chapot pressure cooker” technique

Abstract

In some vein of galen aneurysmal malformation (VGAM) patients, transvenous embolization (TVE) is an attractive option, but its safety is unclear. Here we report the first two VGAM patients treated using the Chapot “pressure cooker” technique (ChPC).

Methods

Two patients, one 5-year-old and one 7-year-old, both presented with congestive heart failure in the newborn period and were subsequently treated in the newborn period with multiple, staged TAEs with n-BCA for choroidal VGAMs.

Results

We achieved progressive reduction in shunting and flow but were unable to accomplish complete closure of the malformation: in both patients, a small residual with numerous perforators persisted. The decision was made to perform TVE using the CHPC. In this technique, a guiding catheter is placed transjugular into the straight sinus (SS). One or two detachable tip microcatheters are advanced to the origin of the SS. Another microcatheter is advanced and the tip placed between the distal marker and the detachment zone of the former. Coils and n-BCA are used to prevent reflux of Onyx.

Conclusions

In this study, we recognized two important factors of traditional VGAM treatment that may cause interventionalists to consider the ChPC to treat VGAM: (1) without liquid embolic, deployed coils may not occlude the fistula entirely. (2) There is the concern of causing delayed bleeding should the arterial component of the fistula rupture. ChPC ameliorates these issues by offering complete closure of the fistula with liquid embolic material in TVE.

Introduction

Vein of Galen Aneurysmal Malformation (VGAM) is a rare, congenital, cerebrovascular disorder which arises between weeks 6 to 11 of gestation. ¹ While only 1% of cerebrovascular malformations are VGAM, it accounts for 30% of all pediatric vascular malformations.^2,3 VGAMs are characterized by a highly dilated draining persistent medial prosencephalic vein of Markowski, the precursor of the vein of Galen (VOG), and the arteries of the limbic system; including the pericallosal arcade (anterior cerebral arteries), and the choroidal arcade (posterior medial, posterior lateral and anterior choroidal arteries). Technical and technological advancements in endovascular embolization along with better understanding of the clinical, anatomic, and pathophysiological features have resulted in significantly improved outcome and prognosis in VGAM. ⁴ Endovascular embolization is currently the gold standard treatment for VGAM. ⁵ Embolization is generally staged, performed over the course of several sessions. In the newborn, a major goal is control of heart failure by reducing flow to the malformation. In older children and those previously treated in the newborn period, the main goal is reduction or reversal of venous hypertension to improve cerebrospinal fluid (CSF) reabsorption which prevents hydrocephalus by reducing shunting. The ultimate goal of embolization is to safely close the malformation.

Staged trans-arterial embolization (TAE) has been our treatment of choice for VGAM to progressively obliterate the fistulous sites with minimal risks. Mortality rates have dwindled significantly as technology and techniques progress with most VGAM children treated with TAE developing normally following appropriately timed treatment. TAE, in our hands, has allowed for total obliteration in 80% of cases, with an 8.9% permanent morbidity rate and a 4.4% mortality rate; ⁴ however, as cases grow more complex proportional to the time since their newborn period, there is an increasing number of VGAMs that remain technically challenging to completely obliterate. When residual, arterial supplies to the malformation are through small perforators or trans-mesencephalic arteries after multiple TAEs, transvenous embolization (TVE) is an attractive option to achieve complete closure of the malformation. Chapot et al. developed a unique technique for the treatment of arteriovenous malformations (AVMs) from a TAE (or TVE) which they titled, “the pressure cooker technique.” ⁶ This technique employs at least two microcatheters: (1) a distally placed catheter which has a detachable segment and is used for the delivery of liquid embolics, and (2) a proximally placed microcatheter to deliver a combination of coils and liquid adhesive cyanoacrylate embolic agent. The proximal microcatheter traps the distal catheter‘s detachable tip and subsequently prevents reflux. ⁶ In this technical report we present an application of TVE with the Chapot pressure cooker (ChPC) technique in two cases of VGAM.

Material and methods

This study was approved by the Institutional Review Board (IRB) at our institution. Clinical and radiological data were obtained retrospectively from our database between July 2019 and July 2020. All patients with VGAM treated using the transvenous ChPC technique in our practice were included in our analysis. This retrospective review was performed after obtaining IRB approval with a waiver of informed consent. All procedures were performed under general anesthesia. In all patients, arterial and venous accesses were obtained under ultrasound guidance. No bolus heparin was given, but a heparinized saline flash line was used. A 5F Glidesheath Slender (Terumo, Tokyo, Japan) was placed in the right femoral artery. In the case of bilateral iliac artery occlusion, the right brachial artery was accessed instead. Full diagnostic cerebral angiograms were performed and it was confirmed that neither internal cerebral veins (ICV) drained into the malformation or nearby. A 5F Envoy (Cerenovus, Irvine, CA, USA) was placed in the vertebral artery for a control angiogram and for the TAE stand-by. Once completed, a 7F Pinnacle (Terumo, Tokyo, Japan) was placed in the right jugular vein. A 7F FUBUKI guiding catheter (Asahi Intecc, Nagoya, Japan) was coaxially navigated over a 125 cm 5F Berenstein-shaped diagnostic catheter and a 0.035-inch Glidewire into the falcine or straight sinus. A retrograde micro-catheterization of the VOG was then achieved with either one or two Apollo 3-cm detachable-tip microcatheters (Medtronic, Irvine, CA, USA) for injection of EVOH. The first detachable-tip microcatheter was navigated over the CHIKAI 008 microwire (Asahi Intecc) and placed in the main pouch of the VOG at the fistulous point. If a separate fistula in a different venous pouch was identified, a second Apollo 3-cm detachable-tip microcatheter was placed into it as well. If needed, a third microcatheter (Headway 17, MicroVention, Tustin, CA, USA, or Apollo) was placed between the first and second markers of the Apollo microcatheters for coil placement. Systolic blood pressure was lowered below 70 mmHg to lower the chance of venous reflux of the embolic materials, and coiling was initiated to start creating the plug. Electrically detachable Barricade coils (Blockade Medical, Irvine, CA, USA) were deployed through the Apollo catheter and Hydrosoft coils (MicroVention) were deployed backwards through the Headway microcatheter. Coils were deployed until the coil mass reached the detachment-marker of the Apollo catheters. Once the vein was packed with coils firmly, EVOH (Onyx-18, Medtronic) was injected through the initial microcatheter intermittently to fill the pouch and the feeding arteries as they enter the vein of the VGAM. Once the EVOH filled into the coil plug and blood flow in the vein was nearly obstructed, acrylic glue (50% n-BCA Trufill, Cerenovus) was injected into the coils through the coiling microcatheter to block the venous segment completely. EVOH was injected further into the VGAM in a retrograde fashion until the entire lesion was filled. Once the VGAM was confirmed to be closed completely, all the microcatheters and the guiding catheters were removed without any issue. The patients were extubated and managed in the pediatric ICU. Systolic blood pressure was maintained between 80–100 mmHg for 48 h.

Results

We present two cases of VGAM treated with transvenous ChPC by our practice between July 2019 and July 2020.

Case 1

A newborn baby female with a Choroidal VGAM presented to our practice (Figure 1(a)). She underwent four trans-arterial n-BCA embolizations over eight years which permitted us to control the presenting heart failure in the newborn period. She developed normally and displayed significant decreases of flow and shrinking of the draining vein by the age of six (Figure 1(b)). We were unable to access the femoral artery again due to the transfemoral access utilized during the newborn period. At the age of six she underwent TVE using ChPC. A 7F guiding catheter was placed in the falcine sinus. Two detachable-tip Apollo 3-cm tip microcatheters were placed in the dilated VOG at the fistula sites and a Headway 17 microcatheter was placed between the detachable markers of the two microcatheters (Figure 1(c) –A1 / 1(c)-A2 / 1(c)-H). Under induced hypotension, the dilated VOG was coiled to trap the detachable tip of the distally placed microcatheter, and Onyx 18 was injected to close the fistula until the cast confirmed complete filling (Figure 1(d/e)). The follow up angiogram showed complete occlusion of the VGAM (Figure 1(f)). In the pediatric ICU, strict blood pressure control and frequent neurological checks were instituted for 48 h post-procedurally. The child continues to develop normally.

Figure 1.

Case 1 choroidal VGAM – Newborn baby female (a) received four prior n-BCA TAEs which controlled CHF, caused significant decrease of flow, and shrank the draining vein by the age of eight (b). A 7F guiding catheter was placed in the falcine sinus (C) through a transfemoral venous approach with radial artery monitoring. Two detachable-tip Apollo 3-cm microcatheters were placed in the dilated vein of Galen at the fistula site (c-A1/c-A2), and Headway 17 microcatheter was placed between their detachable markers for coiling (c-H). Under hypotension, the dilated vein of Galen was embolized with EVOH liquid embolic material (Onyx 18) was injected to close the fistula (d). The cast confirmed a complete filling of the fistula (e). Complete occlusion of the VGAM was confirmed in the follow up angiogram (f).

Case 2

A newborn boy originally presented to our practice with a Choroidal VGAM with severe heart failure (Figure 2(a)). He was originally treated trans-arterially through umbilical access. In the intervening years, a total of 14 trans-arterial n-BCA embolizations of the choroidal feeders and ONYX embolization of the recruited dural supply shrank the VGAM significantly over seven years by the age of eight (Figure 2(b)). At the age of 8, with normal development, he underwent transvenous ChPC embolization. The right jugular was accessed with a 7F guiding catheter which was placed in the falcine sinus. Two detachable 3-cm tip Apollo microcatheters were placed in the dilated VOG at the site of the fistula (Figure 2(c) – A1 /2(c)-A2). Under hypotension, the dilated VOG was coiled to trap the distal, detachable-tip microcatheter and Onyx 18 was injected (Figure 2(d)). The Onyx injection was noted to migrate toward the guiding catheter; subsequently, 0.8 cc of 50% N-BCA was injected through the 2nd Apollo microcatheter, between the detachable markers of the 1st Apollo. This prevented further reflux by making the plug tighter, after which Onyx could penetrate further into the complicated network (Figure 2(e)). The follow up angiogram confirmed complete occlusion of the VGAM (Figure 2(f)). In the pediatric intensive care unit, strict blood pressure control and frequent neuro check was performed for 48 h post procedurally. The patient has had normal development.

Figure 2.

Case 2– A newborn boy originally presented with a choroidal VGAM (a). A total of 14 n-BCA or ONYX TAEs of the recruited dural supply shrank the VGAM significantly by the age of six (b). A 7F guiding catheter was placed in the falcine sinus through a right cervical transjugular approach and two detachable Apollo-tip 3 cm microcatheters were placed in the dilated VOG at the fistula (c-A1/A2). Under hypotension, the dilated VOG was embolized with EVOH liquid embolic material (d). Following this, the liquid embolic penetrated nicely into the complicated network (e). Complete occlusion of the VGAM was confirmed in the follow up angiogram (f).

Discussion

TVE for VGAM was first introduced in 1986 by Mickle et al. who described transtorcular coiling in a cohort of three patients. ⁷ Additional publications followed but all agreed that transvenous coiling was a last-resort to be used in patients who had experienced unsuccessful TAEs. ⁸ The risk of hemorrhage was significant in these cohorts and this approach was not revisited until decades later. There has only been one previous report about TVE of VGAM after multiple sessions of TAE. ⁹ Orlov et al. successfully attempted TVE with ONYX and reported no procedure-related morbidity or mortality at six-month follow-up. Our study was driven by investigating two important issues in the field of VGAM treatment: (1) achieving complete closure of the VGAM fistula, including the residual vein, while (2) avoiding drainage impairment of the normal brain. ChPC allows for complete obstruction of the residual draining vein to force liquid embolic to close the incoming arterial supply and prevent delayed hemorrhage. Considering the high-flow of VGAMs relative to typical AVMs (no nidus) but also prior TAE embolization, lowering blood pressure to 70 mmHg is sufficient to prevent venous reflux or hemorrhagic complications. Assuring the ICV is not included in the drainage network of the VGAM is a crucial aspect of identifying candidates for TVE ChPC to avoid impairing drainage of the normal brain. This is best achieved through a bilateral carotid angiogram to ascertain that no obvious ICV involvement is observed. Furthermore, reflux of EVOH to the normal artery can be prevented by understanding arterial anatomy well during the multiple sessions of TAE. In endovascular treatment of the VOG malformation, TVE is feasible option, once the dilated VOG becomes sufficiently constricted. Though the dural sinuses sometimes occlude after multiple sessions of endovascular embolization, ¹⁰ transvenous approach through the internal jugular vein and transverse-sigmoid sinus was possible and the fistula remained accessible. In cases of occlusion, angioplasty or stenting is justified if needed.^11–13

Conclusion

Typical TVE approaches are often argued against due to the higher perioperative morbidity mortality rates and chances of reflux. We recommend performing ChPC in conjunction with preemptive TAE to systemically reduce the size of the lesion and improve the safety of TVE procedures. The ChPC technique is unique in that it allows for a higher injection volume of liquid embolic to be delivered while significantly ameliorating the risks of reflux. To prevent incomplete occlusion or post procedural hemorrhagic complication in transvenous VOGM treatment, ChPC using EVOH liquid embolic material is useful and should be incorporated in the neurointerventionalist‘s arsenal.