The proSA is the first hydrocephalus valve that enables post-operatively the adjustment of the opening pressure in the upright position, as well as for all angles of elevation between the upright and the supine positions. This opening pressure depends on the body position of the patient. In addition to the proSA, a differential pressure valve (such as the miniNAV) or a programmable valve (such as the proGAV) should be implanted.
The upper depiction shows a schematic cross section of the proSA. The proSA is composed of a robust titanium casing whose proximal end contains a ball-cone valve. A coil spring determines the opening pressure of the ball-in-cone valve and the sapphire ball ensures the precise closure of the valve.The weight is connected to the spring and keeps the sapphire ball in its position. In this way, optimal CSF drainage is ensured for each individual patient in any body position. The tension of the spring, and thus the valve opening pressure, can be adjusted by turning the rotor magnetically, with the valve implanted under the patient's skin. The cerebrospinal fluid flows in through the inlet port and flows out by way of the outlet port.
With the proSA in horizontal position, the weight does not affect the sapphire ball. Hence, in this configuration the proSA is open, and the force brought to bear by the weight does not counteract the fluid pressure. The ventricular pressure is now controlled solely by the optional differential pressure valve installed.
In the vertical position, the proSA and the differential-pressure valve work together. The total opening pressure is the sum of the opening pressures of the DP-valve and the proSA. If the IVP (intraventricular pressure) of the patient and the hydrostatic pressure exceed this pressure, the closing ball of the proSA is pushed away from the cone seal and a gap opens for fluid drainage. The valve system prevents increases in intraventricular pressure above the physiological range.