SHUNTASSISTANT (SA) /
paedi-SHUNTASSISTANT - description |
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| Fig. 1 |
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| Fig. 2 schematic cross section of the SHUNTASSISTANT |
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| Fig. 3 |
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| Fig. 4 |
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| The SHUNTASSISTANT 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. mini-NAV) or an adjustable pressure valve. The SHUNTASSISTANT can be implanted either upstream or downstream from the primary valve. In other words it can be integrated anywhere in the tube system. |
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| The weight of the tantalum ball generates the counterbalance to the hydrostatic pressure in the shunt system. The SHUNTASSISTANT functions precisely and reliably according to the patient's posture and is unaffected by changes in subcutaneous pressure. |
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The paedi-SHUNTASSISTANT works in the same way as the SHUNTASSISTANT. However it is considerably smaller and its functions are intended to meet the special needs of those with pediatric hydrocephalus. |
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| The paedi-SHUNTASSISTANT should be implanted retroauricularly while the SHUNTASSISTANT should be implanted in the chest (thorax).
The paedi-SHUNTASSISTANT and the SHUNTASSISTANT are posture-dependent valves and thus implantation parallel to the body axis is required. |
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| Function |
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Fig. 2 shows a schematic cross section of the SHUNTASSISTANT and the paedi-SHUNTASSISTANT.
The inner construction is shown in Fig. 3. 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).
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| Horizontal position |
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| 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 (Fig.4) in the supine position, since the tantalum and the sapphire balls stay in position and allow CSF to pass. |
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| Vertical position |
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| As soon as the patient stands up, the (paedi-) SHUNTASSISTANT 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.
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