FIGURE 1. (A) Illustration depicts the structure of the Codman-Hakim programmable valve from the side view. The flat spring (white arrowheads) presses the valve ball landed on a matching valve seat (black arrowheads) through which cerebrospinal fluid (CSF) is passed distally as well as the pressure control cam (short black arrow) which controls the intensity of the flat spring. These structures are built on the base plate (short white arrows). Long white arrows indicate the direction of CSF flow. (B) Illustration depicts the valve from the top view. The bottom side of the cam has a protrusion of "X" (white asterisk) in the center and this part is fixed to a corresponding X-shaped slit on the base plate by the pressure of the flat spring.