Examination of deposits in cerebrospinal fluid shunt valves using scanning electron microscopy

Abstract

Obstruction remains the most common complication of cerebrospinal fluid shunts. The valve constitutes an important site of potential malfunction. The aim of this pilot study was to investigate the extent and composition of debris depositions along the structural components of the shunt valve. We examined three explanted Medos programmable valves. The valves were stored and examined wet. They were cut open and disassembled. All specimens were studied under a scanning electron microscope (SEM; Quanta 200; FEI, Hillsboro, OR, USA) operating at different levels of accelerating voltage and 110 μA beam current. Valve areas analyzed included the ruby ball and collar, the flat spring with its pillar, and the staircase cam. The elemental composition, in areas with abnormal deposits, was subsequently determined by energy-dispersive X-ray microanalysis (EDS) using a Si (Li) detector (Sapphire; EDAX, Mahwah, NJ, USA) with a super ultrathin Be window. All explanted valves had varying degrees of deposits in all surveyed areas. The extent of the deposits was not related to the time since implantation. The effect of these deposits on proper functioning of the valve as well as their pathogenesis is difficult to establish.