A differential pressure valve opens when a certain pressure difference is reached between the brain and the abdominal cavity - regardless of whether you are lying down or standing up. The problem is that gravity has an additional effect when the patient is standing, which can cause too much cerebrospinal fluid to drain out (overdrainage). To avoid this, a valve with a higher opening pressure is usually implanted. However, this can lead to too little drainage when the patient is lying down (underdrainage). The opening pressure of a differential pressure valve is a compromise between lying and standing.

This is where a gravitational valve comes in: It includes an additional component that recognises whether you are lying down or standing up. Gravitational valves consist of two units: a differential pressure unit that regulates the opening pressure when you are lying down and a gravitational unit that is only activated when standing up.

• When lying down: As the head and abdomen are at approximately the same height, there is no additional gravitational force acting on the shunt system. The differential pressure unit ensures that cerebrospinal fluid is only drained when the pressure in the brain exceeds a certain value. This enables sufficient but controlled drainage.
• Standing up: The head is significantly higher than the abdomen. Gravity creates an additional pressure difference that would increase the drainage. To prevent this, the gravitational unit becomes active: it increases the opening pressure of the valve so that cerebrospinal fluid only flows out when it is really necessary. This prevents too much cerebrospinal fluid from being drained (overdrainage).

Gravitational valves therefore ensure personalised drainage - without any compromises. The principles described above are also relevant in LP shunts, except that in this case there is a suction effect when the patient is standing. The gravity valves from MIETHKE are therefore suitable for both VP shunts and LP shunts.