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Cranial Pressure Sensor

Pressure build-up inside the cranium, is one of the most dangerous physical conditions to threaten the brain. In some individuals, fluid build-up is so intense that it risks crushing the brain. The only way to deal with it, is usually to open up the skull and install a shunt, to pump the excess fluid out. In some individuals two or more shunts are required, along with frequent hospital visits to monitor the condition.

Medical science is so-far at a loss to explain why this cerebral fluid pressure suddenly increases is some individuals. Once it has increased once however, that individual remains susceptible, and another pressure increase could occur at any time. The consequences however, are always disastrous and become progressively worse the longer it goes untreated.

Increasing fluidic pressure has many effects. Primarily it places increasing strain on the blood vessels on the surface of the brain; squeezing them tighter and eventually closing them off. Parts of the brain then die off due to lack of oxygen. This damage is of course permanent and often leads to dementia. As many as 10% of all dementia cases are thought to be caused by such fluid-related pressure.

Thought because without knowing what to look for, cerebral fluid pressure has always been difficult to diagnose. In order to detect it, the only diagnosis method that works, is to drill a small hole in the brain, and insert a probe through the hole, from the skullcap itself, down to the surface of the brain. A cable keeps the probe connected to a measuring device, and the patient must stay like this for up to a week, due to natural variation in fluid pressure. Only the averaged pressure readings for that week can be used to determine if the pressure is abnormally high. The patient is of course confined to a bed for this procedure, and so it cannot be done in a timely manner to every patient with suspected cerebral fluid pressure problems, due to the limited number of available beds in hospital wards. In the meantime, to those with high fluidic pressure, damage to the brain is mounting.

Obviously another solution is needed.

The prototype Sensor

The obvious next-step solution is to remove the cable connecting the patient to the monitoring device, so as to greatly increase their freedom of movement, and open up the possibility of diagnostic treatment in the patient's own home and workplace. Another step also required, is to bypass drilling a hole through the skull in the first place. If the diagnosis can be carried out from outside the head, it removes the necessity for a delicate surgery in the first place, and reduces the risk to the patient.

Researchers at the Fraunhofer Institute for Biomedical Engineering IBMT in St. Ingbert, Germany, may have achieved both steps. They have developed a small, waterproof sensor that can be affixed to the outside of the skull.

From the outside, the probe resembles a thick button cell battery. It is only about one centimetre high, two centimetres wide and in the future, should get even smaller. Resting on its inside is a pressure sensor made of silicon, similar to those sensors used today in automobiles, to handle the demanding measurement tasks.

“The cover of the tiny metal container is made from a pliable metal membrane that reacts to pressure changes in the brain,” as project manager Dr. Thomas Velten, manager of the department of biomedical microsystems at IBMT, describes the unique aspects of the system. This pressure is transmitted to the silicon chip on the inside. The measurement value is transmitted to the measuring device outside the body through a radio impulse. “The benefits are immense,” says Velten. “The patient no longer has to be checked in on an inpatient basis but  comes to the clinic for a brief measurement appointment instead.”

The sensor is read from the outside within seconds. It operates without batteries, since it is activated by the reading device. Thus, the patient can wear it for several months, or even a number of years, without requiring additional surgery.


Pressure switch inside the head

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