Hydrocephalus: sensors monitor cerebral pressure

Urinary incontinence, a shuffling gait, and deteriorating reasoning skills are all indicators pointing to a Parkinsonian or Alzheimer type disease. An equally plausible explanation is hydrocephalus, commonly known as “water on the brain.” With this diagnosis, the brain produces either too much cerebral fluid, or it cannot “drain off” these fluids with adequate sufficiency. The consequence: Pressure in the brain rises sharply, resulting in damage. A shunt system – a kind of silicon tube that physicians implant into the patient’s brain, provides relief. It draws off superfluous fluid from there, for example, into the abdominal cavity. The heart of this shunt system is a valve: If the pressure increases above a threshold value, then the valve opens; if it declines again, then the valve closes.

In rare cases, over-drainage may occur. The cerebral pressure lowers too much, the cerebral ventricles are virtually squeezed out. Until now, physicians could only detect and verify such over-drainage through elaborate and costly computer and magnetic resonance tomography.

Cerebral pressure measurable anytime

With a new kind of sensor, things are different: If it is implanted into the patient’s brain with the shunt system, the physicians could read out brain pressure using a hand-held meter: within seconds, anytime and without complex investigation. Researchers at the Fraunhofer Institute for Microelectronic Circuits and Systems IMS in Duisburg, working jointly with Christoph Miethke GmbH and Aesculap AG, engineered these sensors.

If the patient complains of discomfort, then the physician merely needs to place the hand- held meter outside, on the patient’s head. The device sends magnetic radio waves and supplies the sensor in the shunt with power- the implant is “awakened,” measures tem- perature and pressure in the cerebral fluid, and transmits these data back to the handheld device. If the pressure on the outside of the desired area, the physician can set the valve on the shunt system from the outside as needed, and individually adjusted to the patient. “The sensor is an active implant, which also takes over measurement functions, in contrast to a stent or a tooth implant,” says Michael Görtz, head of pressure sensor technology at IMS.

The implant must be biocompatible; the body cannot reject it. Researchers had to ensure that the body also would not attack the implant. “The defense response behaves just like an aggressive medium, that would even dilute the silicon of the electronics over the course of time,” explains Görtz. Miethke therefore completely encases the implant into a thin metal casing. “We can still supply it with power from the outside through the metal casing, measure cerebral pressure through the housing and transmit the recorded data outside, through the metal to the reader,” Görtz explains. To do so, the correct metal had to be found. The coating may not be thicker than the walls of a soft drink can – in other words, much thinner than one millimeter. The researchers even developed the handheld reading device, together with the electronics, through which it communicates with the sensor.

The sensor is ready for serial production, and was already approved by Miethke. The company has already initiated the market launch of the system. “The sensor sets the basis for the further development through to theranostic implants – a neologism derived from the words “therapy” and “diagnostic.” In a few years, the sensor could then not only record cerebral pressure and develop a diagnosis on the basis of this, but also properly adjust the pressure independently, immediately on its own and thus, take over the therapy process,” says Görtz.

Rainfall, brain infection linked in sub-Saharan Africa

The amount of rainfall affects the number of infant infections leading to hydrocephalus in Uganda, according to a team of researchers who are the first to demonstrate that these brain infections are linked to climate.

Hydrocephalus — literally “water on the brain” — is characterized by the buildup of the fluid that is normally within and surrounding the brain, leading to brain swelling. The swelling will cause brain damage or death if not treated. Even if treated, there is only a one-third chance of a child maintaining a normal life after post-infectious hydrocephalus develops, and that chance is dependent on whether the child has received the best treatment possible.

"The most common need for a child to require neurosurgery around the world is hydrocephalus," said Steven J. Schiff, the Brush Chair Professor of Engineering, director of the Penn State Center for Neural Engineering and a team member.

In sub-Saharan Africa, upward of 100,000 cases of post-infectious hydrocephalus a year are estimated to occur. The majority of these cases occur after a newborn has suffered from neonatal sepsis, a blood infection that occurs within the first four weeks of life, the researchers reported in a recent issue of the Journal of Neurosurgery: Pediatrics.

Benjamin C. Warf, associate professor of neurosurgery, Harvard Medical School, Boston Children’s Hospital, noticed that about three or four months after an infant in East Africa had an infection like neonatal sepsis, the child would often return to the clinic with a rapidly growing head — hydrocephalus. Schiff joined Warf to help figure out what caused this disease so frequently.

Schiff and colleagues tracked 696 hydrocephalus cases in Ugandan infants between the years 2000 and 2005. The researchers obtained localized rainfall data for the same time frame through NOAA (National Oceanic and Atmospheric Administration) weather satellites using the African Rainfall Estimation Algorithm developed at the U.S. NOAA Climate Prediction Center.

Uganda has two peak rainfall seasons, in spring and fall. By comparing the data from NOAA and the hydrocephalus cases, the researchers found that instances of the disorder rose significantly at four different times throughout the year — before and after the peak of each rainy season, when the amount of rainfall was at intermediate levels. In Uganda an intermediate rainfall is about 6 inches of rain per month.

Schiff and colleagues previously noted that different bacteria appear associated with post-infectious hydrocephalus at different seasons of the year. While the researchers have not yet characterized the full spectrum of bacteria causing hydrocephalus in so many infants, they note that environmental conditions affect conditions supporting bacterial growth, and that the amount of rain can quench bacterial infections. The moisture level clearly affects the number of cases of hydrocephalus in this region of East Africa.

"Hydrocephalus is the first major neurosurgical condition linked to climate," said Schiff, who is also professor of neurosurgery, engineering science and mechanics, and physics, and a faculty member of the Huck Institutes of the Life Sciences. "This means that a substantial component of these cases are almost certainly driven from the environmental conditions, and that means they are potentially preventable if we understand the routes and mechanisms of infection better."