Purpose: Shunt valves, required for treatment of hydrocephalus, demand for high performance rates and lifelong excellent function. To overcome problems with traditional silicone materials, adjustable and gravity-adapted titanium valves were developed. Even modern shunt valve systems are still subject to occlusion. The aim of the present study was to investigate dysfunctional silicone and titanium valves for presence of cellular and proteinous materials inside the housings by means of histopathology.
Methods: A total of 19 explanted shunt valves from children between 2 and 182 months of age were investigated following dysfunction. After fixation in formalin and embedding in hard resin, slices were ground to a thickness of 5-30 μ. Besides standard histology, immunohistochemistry was performed using antibodies with markers for microglia, astrocytes, platelets, monocytes, and the proteins laminin, fibronectin, and collagen IV.
Results: Traces, layers, and plaques could be demonstrated in every investigated silicone or titanium valve with an implantation time of more than 6 days. Most of the tissue was found adjacent to silicone and titanium surfaces of the inner housing, the adjustment rotor, and ball-in-cone core. Markers for micro and astroglia stained positive in 40-60% of the specimen, mostly demonstrating a proteinous layer positive for laminin (80%), fibronectin (30%), and collagen IV (30%).
Conclusions: Tissue reactions with formation of cellular and proteinous matrix components are common in obstructed silicone and titanium shunt valves. The tissue mimics astrocytic repair mechanisms genuine for basilar membrane matrix. The knowledge of these typical arachnoid patterns of colonization is a prerequisite for developing future shunt devices.
Keywords: Astrocytes; Extracellular matrix; Hydrocephalus; Microglia; Titanium shunt valve.