WEB™ SL: Intrasaccular Flow Disruptor for Wide-Neck Bifurcation Aneurysms Without DAPT

The WEB™ SL (Woven EndoBridge Single Layer) is a self-expanding nitinol mesh device from MicroVention Terumo designed for endovascular treatment of wide-neck bifurcation aneurysms. It is deployed entirely within the aneurysm sac — no portion of the device extends into the parent artery — where it disrupts intra-aneurysmal flow and promotes thrombosis. This intrasaccular design is the WEB’s defining advantage over stent-assisted coiling: because no implant crosses the aneurysm neck into the parent artery, DAPT is not required, making WEB SL the preferred option for patients who cannot tolerate prolonged dual antiplatelet therapy.

The WEB SL has a cylindrical-bilobed shape with a waist at mid-height. In the aneurysm sac, the proximal and distal lobes expand against the sac walls while the waist conforms to the neck, creating flow disruption across the neck. The mesh creates a high-resistance barrier to inflow, progressively reducing intra-aneurysmal flow velocity until the sac thromboses. Complete angiographic occlusion typically develops over 6–12 months, though adequate neck coverage — the primary determinant of treatment success — is visible immediately after deployment.

The WEB SL is available in a range of width and height combinations covering sac diameters from 3 mm (delivered via VIA 17) to 11 mm (VIA 33). Sizing is based on three-dimensional DSA measurement of the sac: WEB SL width is sized to the mean of the aneurysm’s maximum width (W) and maximum height (H), rounded up to the nearest 0.5 mm. The WEB SL is sized 0.5–1.0 mm larger than the mean sac dimension to ensure adequate wall apposition and neck coverage.

VIA microcatheter selection matches WEB size: VIA 17 for WEB 3–7 mm; VIA 21 for 7–8 mm; VIA 27 for 8–9 mm; VIA 33 for 10–11 mm. The V-Grip device delivery and repositioning handle and the WEB Detachment Controller are standard accessories required for all WEB procedures.

The WEB SL has the most robust clinical evidence of any intrasaccular device. WEBCAST (2016) demonstrated 53.8% complete occlusion and 85.5% adequate occlusion (complete plus neck remnant) at 12 months for MCA, AComA, and basilar apex aneurysms treated with WEB. The WEB-IT trial (2018) confirmed these results in a North American multicentre cohort, with 59% complete occlusion and 84.6% adequate occlusion at 12 months.

WEBCAST 2 extended follow-up to 36 months, showing continued improvement in occlusion rates over time — a unique characteristic of flow-disruption therapy where occlusion continues to mature beyond the 12-month imaging endpoint of most coiling studies. The combined evidence base positions WEB SL as a first-line option for wide-neck bifurcation aneurysms at experienced neurointerventional centres.

WEB SL is ideally suited for wide-neck bifurcation aneurysms at the MCA bifurcation, anterior communicating artery (AComA), anterior cerebral artery (ACA), basilar apex, and ICA terminus. These are locations where the aneurysm neck spans a vessel bifurcation with one or two branches arising from the neck area, making coil herniation into the branches a risk with primary coiling and stent-assisted coiling requiring DAPT.

Patient-specific factors that further favour WEB include: ruptured presentation (DAPT is contraindicated in the acute phase when anticoagulation is necessary); older age where long-term DAPT carries elevated bleeding risk; patients on oral anticoagulation for atrial fibrillation or other indications; and patients requiring early non-cardiac surgery within 6–12 months of aneurysm treatment.

Modern Medical Solutions is the authorised MicroVention Terumo distributor for Tajikistan and Afghanistan. WEB SL is available across the full size range with the companion VIA microcatheter family for neurointerventional programmes in Tajikistan and Afghanistan.

Contact Modern Medical Solutions to discuss WEB SL alongside WEB SLS, VIA microcatheters, V-Grip, and WEB Detachment Controller as a complete WEB treatment system.