Engineering a Middle Meningeal Artery Embolization Model with Hydrophilicity and Hydraulic Resistance

PROJECT SUMMARY Chronic subdural hematoma (cSDH), a neurological disorder characterized by abnormal blood accumulation the surface of the brain, is often treated by surgical evacuation of the blood. However, the recurrence rate of this approach remains high (up to 20%). Data from recent randomized clinical trials demonstrate endovascular treatment of cSDH via embolization of the middle meningeal artery (MMA) significantly reduces recurrence compared to surgery. Thus, cSDH MMA embolization is poised to become standard of care, with the number of procedures projected to surpass that of endovascular therapy for large vessel strokes. Positive outcomes with cSDH MMA embolization have been demonstrated with existing embolic agents including polyvinyl alcohol particles, Onyx and its derivatives, and n-butyl cyanoacrylate glues (regulatory approval of these agents specifically for this indication is underway). At least two next-generation biomaterial embolic agents (NeoCast™ Embolic System and IMPASS™ Embolic Device) are also being developed for cSDH MMA embolization. The rapid growth of cSDH MMA embolization highlights a need for a vascular bench model that trains clinicians on the use of various embolic agents. The model will serve as an important first step in neurointerventional education, especially for agents with steep learning curves. We have already developed a first-generation, silicone MMA model using cSDH patient data. The model has multiple target sites for injection, can be used under fluoroscopy, and allows angiographic occlusion assessment. Unfortunately, the hydrophobic nature of silicone and absence of a capillary bed may alter the flow and distribution of an embolic agent; it also precludes testing of liquid agents that occlude in a distal to proximal fashion (e.g., n-butyl cyanoacrylate glue and NeoCast) as there is no backstop to prevent material flow-through. To address these issues, we propose to enhance our model by more accurately replicating the in vivo environment. First, we will hydrophilize the silicone model to have a water contact angle similar to blood vessels. This will be accomplished using either hydrogel surface-coating or hydrophilic polydimethylsiloxane tethering techniques. Second, we will integrate a hydraulic barrier (leveraging unique porous morphology of polyurethane foams) that creates fluid flow resistance (e.g., pressure drop) similar to that of a capillary bed and acts as a backstop to prevent material flow-through. Experienced neurointerventionalists will perform injections in the improved model with PVA particles, Onyx, and n-butyl cyanoacrylate. They will provide feedback on face validity (the resemblance of the model to real-life scenario) and content validity (effectiveness as a training tool for cSDH MMA embolization). Subsequently, embolization performance (e.g., ease of injection, injection time, embolic radiopacity, angiographic occlusion) of NeoCast in the model will be compared to that of the existing agents. This project will deliver a robust bench training model for neurointerventionalists to learn procedural skills and use of current and next-generation embolic agents for cSDH MMA embolization, which will ultimately benefit patient care.