Brain Fluid Sensor May Improve Hydrocephalus Treatment

A patented volume sensor could better regulate cerebrospinal fluid (CSF) flow in hydrocephalus patients by accurately measuring intracranial ventricular fluid volume, and keeping it constant using an active feedback control mechanism.

Researchers at the University of Illinois (Chicago, USA) developed a novel impedance sensor for direct brain ventricular CSF volume measurements, based on a model that emulates the expansion of the lateral ventricles, as seen in hydrocephalus. The sensor prototypes were fabricated and tested by injecting CSF into a lab model and withdrawing it cyclically in a controlled manner, with volume measurements tracked over eight hours; the pressure measurements recorded were found to be comparable to conditions seen clinically. The results obtained from the bench-top model served to calibrate the sensor for preliminary animal experiments.

In the second part of the experiment, a hydrocephalic rat model was used to validate a scaled-down, microfabricated prototype sensor. CSF was removed from the enlarged ventricles and a dynamic volume decrease was properly recorded in short-period experiments, measuring the volume of fluid removed over a few hours. The researchers will further assess the animal model over several weeks to see if the tracking of ventricular size is accurate following shunting. The researchers also hope that the new designs will accelerate future medical device design, by determining sensor specifications and optimization in a rational process. The study was published ahead of print on May 24, 2010, in IEEE Transactions of Biomedical Engineering.

"One of the biggest problems with shunts is they either drain too much--so brain ventricles, or cavities, completely collapse--or drain too little,” said lead author Andreas Linninger, Ph.D., an associate professor of bioengineering. "Either way, it's not the best outcome for patients.”

A surgically implanted shunt system that relies on pressure to discharge fluid and diverts excess CSF from the brain to a part of the body where it can be absorbed--usually the abdomen--has long been the preferred treatment for hydrocephalus. But shunts are unreliable and often fail after implantation, since they are passive, affected by posture, activity, and even altitude. Current monitoring options of shunt performance involve magnetic resonance imaging (MRI) or pressure monitors; however, there are no existing methods for continuous cerebral ventricle volume measurements.

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