Occlusion of a mural type vein of Galen malformation in a 10-month-old boy with three Woven EndoBridge (WEB 17) and two coils

Abstract

We report the case of a 10-month-old boy with an enlarged head circumference and severe motor developmental delay. MRI showed a vein of Galen malformation (VGAM) with a heavily dilated median prosencephalic vein. Digital subtraction angiography confirmed a mural type VGAM with three feeding arteries arising from the posterior cerebral arteries. Due to the short length of the feeding arteries and the high flow, occlusion of the feeding vessels with detachable coils was not possible because of repeated coil dislocation into the dilated vein. Embolization of the three feeding vessels was then performed with a Woven EndoBridge single layer device (WEB SL17). In two arteries complete occlusion was accomplished with the WEB alone and in one artery additional deployment of two coils was necessary. Follow-up imaging at day 1 after treatment as well as 3 and 9 months after embolization showed persistent occlusion.

Background

To our knowledge, no treatment of a mural type vein of Galen malformation (VAGM) with a Woven EndoBridge (WEB) device has previously been reported.

Case presentation

We present the case of a 10-month-old boy with motor developmental delay diagnosed at the age of 8 months. His head circumference was enlarged. An initial MRI showed an enlarged median prosencephalic vein with a maximum diameter of 5.4 cm consistent with a VGAM. Other than a short segment stenosis distally in the straight sinus and venous collateral pathways via enlarged parieto-occipital cortical veins, no further vascular anomalies were detected. Of note was the dilation of the ventricular system without obvious compression of the ventricular aqueduct (figure 1A).

Figure 1.

Initial MRI (A) shows the heavily dilated median prosencephalic vein and enlarged ventricles. Of note is the stenotic straight sinus. The pre-procedural angiogram (B) shows a jet from the right P2 segment into the dilated vein. Immediately after placement of the first Woven EndoBridge (WEB) device into the right feeding artery, residual inflow can be seen (C). The final angiograms (D, E) demonstrate no residual inflow. Follow-up MRI 9 months after the procedure (F) shows persisting occlusion and significant shrinkage of the dilated prosencephalic vein. The occlusion of the straight sinus was asympomatic.

Treatment

Digital subtraction angiography was performed at the age of 10 months. Via a 4F sheath in the right groin, a 4F guiding catheter was placed in the V1 segment of the left vertebral artery (VA). Injection in the left VA (figure 1B) confirmed a mural VGAM with the largest feeding artery arising from the P2 segment of the right posterior cerebral artery (PCA). An initial attempt to occlude the feeding artery with a coil (Target Ultra 360 3×6, Stryker, Freemont, California, USA) via an Excelsior SL10 (Stryker) failed because of repeated coil dislocation into the dilated vein due to high flow and shortness of the artery.

The coil was removed and, via a VIA 17 microcatheter (Terumo Microvention, Aliso Viejo, California, USA) with an inner diameter of 0.0175 inch, a WEB single-layer device (WEB 17 SL) 4×2 mm was placed in the feeding vessel with a diameter of 2.9 mm as measured on subtracted angiographic images in two perpendicular planes. The distal end of the WEB was placed at the level of the arteriovenous junction of the VGAM. A subsequent angiogram before detachment showed a residual inflow (figure 1C) that ceased approximately 5 min after placement. After occlusion of the largest feeding artery, another feeding vessel arising from the left PCA was visible with a now stronger inflow. This feeding artery with a diameter of 2 mm was occluded with a second WEB 17 SL 3×2 mm. A third feeding artery arising from the right PCA appeared after embolization of the first two vessels. After placement of a WEB 17 SL 4×3 mm, residual blood inflow via this artery was observed. Via the VIA 17 microcatheter, two coils (Target 360 Ultra 3×6 and Target Nano 1×2) were placed proximal to the WEB. During and after deployment of all three devices no movement caused by high flow velocity was noted. The final angiograms (figure 1D,E) showed complete occlusion of the VGAM and regular flow in the PCA. Because of the risk of a fast thrombus formation as a result of the now low flow within the stenotic straight sinus, low molecular heparin was administered for 2 weeks.

The following day a ventriculoperitoneal shunt was placed by the neurosurgeons. MRI control showed no residual inflow and complete thrombosis of the aneurysm sac.

Outcome and follow-up

Follow-up MRI was performed on the first post-interventional day and 3 and 9 months after embolization. All examinations confirmed occlusion and showed shrinkage of the vein from a maximum diameter of 5.4 cm to 2.3 cm on recent follow-up (figure 1E). Of note is the clinical asymptomatic obliteration of the stenotic straight sinus. Venous drainage was maintained by the superficial and deep venous system. Motor and mental development was appropriate to the patient’s age on follow-up clinical examinations.

Discussion

The basic pathology of a VGAM is a high flow arteriovenous fistula with direct drainage of choroidal arteries into the precursor of the vein of Galen, the median prosencephalic vein.¹ The Lasjaunias classification differentiates between choroidal VGAM with multiple small arterial feeders and an interposed arteriovenous network and mural VGAM with one or more arterial feeding vessels draining directly into the venous system.² The goal of endovascular therapy is the restoration of physiological cerebral blood flow and, most importantly, reduction of elevated venous pressure. Given appropriate patient selection and timing of treatment, a favourable outcome can be achieved in more than half of the patients.^{3 4} Complete occlusion of the malformation is not mandatory.¹

To our knowledge, no treatment of mural type VAGM with WEB devices has been reported before. Liquid embolic agents—traditionally cyanoacrylate⁵ and, more recently, precipitating agents such as Onyx⁶—are well suited for choroidal type VGAM. In choroidal type malformations, a combined transarterial and transvenous approach is necessary.1 4 7–9 In cases of mural VGAM, direct occlusion of the feeding arteries via a transarterial access to reduce or stop arterial inflow and allow shrinkage of the dilated vein over time represents the obvious and more simple approach.

As in our patient, because of the shortness of the feeding artery, consecutive coil dislocation into the aneurysm occurred and coiling was not possible. The short, but well-defined, feeding arteries seemed well suited for embolization with the WEB device because a stable positioning due to its high radial force is possible. Another advantage of the only recently available WEB 17 SL is the use of the relatively small-sized VIA 17 microcatheter which facilitates navigation in small vessels.

We oversized the nominal device diameter relative to the vessel diameter by about 30% to ensure a position completely within the feeding vessel. The distal ends of the devices were placed at the level of the arteriovenous junction. In our opinion, protrusion of the devices into the vein should be avoided because of the risk of dislocation into the vein. While some degree of oversizing of the device leads to a stable intra-arterial position, too much oversizing would lead to an unpredictable elongation of the device. Protrusion into the PCA with the subsequent risk of infarction has to be avoided. The clearly visible proximal and distal markers allow for exact placement of the WEB within the feeding artery and verification of its position. During placement no movement of the devices was noted.

Immediately after deployment of each device, residual inflow was noted which ceased in two of the three vessels within 5 min. In one feeder a persisting inflow was seen. Accessory coil placement proximal to the WEB was necessary in one vessel and led to complete occlusion. Post-procedural heparinization is important to prevent excessive thrombosis of essential veins.

Learning points.

• Occlusion of mural type VGAM with the new WEB 17 device seems to be a technically feasible and safe procedure.

• In cases of incomplete feeding artery occlusion, accessory coil deployment is possible.