SHUNTASSISTANT ® (SA) paediSHUNTASSISTANT ® (paediSA)
The SHUNTASSISTANT (SA) is a gravitational valve and is intended as a supplementary valve in order to control the siphon effect. It is used in conjunction with either a conventional (e.g. miniNAV) or an adjustable pressure valve. The SA can be implanted either upstream or downstream from the primary valve. In other words it can be integrated anywhere in the tube system.
The weight of the tantalum ball generates the counterbalance to the hydrostatic pressure in the shunt system. The SA functions precisely and reliably according to the patient's posture and is unaffected by changes in subcutaneous pressure.
The paediSA works in the same way as the SA. However it is considerably smaller and its functions are intended to meet the special needs of those with pediatric hydrocephalus.
The paediSA should be implanted retroauricularly while the SA should be implanted in the chest (thorax).
The paediSA and the SA are posture-dependent valves and thus implantation parallel to the body axis is required.
The upper depiction shows a schematic cross section of the SA and the paediSA.
The function of the paediShuntassistant and Shuntassistant depends on the position(horizontal or vertical) of the patient. Because of that the paSA or SA has to be implanted parallel to the body axis.
In the horizontal body position, the intraventricular pressure is controlled only by the diffential pressure or adjustable valve. The (paedi)SHUNTASSISTANT however has no influence on the drainage of the CSF (shown on the lower depiction) in the supine position, since the tantalum and the sapphire balls stay in position and allow CSF to pass.
As soon as the patient stands up, the paediSHUNTASSISTANT and the differential pressure or adjustable valve work together. If the force exerted by the pressure of the incoming CSF exceeds the weight of the tantalum ball, the sapphire and the tantalum ball are driven up away from the ball seat and CSF will flow through the now open gap and to the outlet port. By this mechanism overdrainage is prevented. The gravitational system adapts to every body position of the patient. The inner construction is shown in the depiction on the right. Both valves consist of a robust titanium housing (1) with an inlet (2) and outlet (3) connector, a tantalum ball (4), a sapphire ball (5) and code rings (6).