A Flow Monitor for Pediatric Hydrocephalic Shunts

DESCRIPTION (provided by applicant): Hydrocephalic shunt dysfunction diagnosis is one of the most complicated and time consuming aspects of treating hydrocephalic infants and young children, since preverbal children cannot describe such critical symptoms as persistent headaches. One must instead rely on observable symptoms that often resemble those of common childhood illnesses. As a result, suspected shunt dysfunction often requires emergency room admission with invasive, costly and often inconclusive diagnostic tests, yet it is estimated that the shunt is actually working properly two out of three visits. From an engineering perspective, a properly functioning drainage shunt should function as drainage tubing with a physician-selected pressure/flow characteristic. One could greatly improve outcomes and reduce patient/parental stress if doctors could non-invasively measure shunt tubing CSF flow over a range of posture-induced pressures to confirm the desired pressure/flow relationship, as an adjunct to assessing shunt patency and shunt under/overdrainage. Transonic Systems, Vygon Neuro and the Children's Hospital of Wisconsin will address this need by developing flow sensor modules that can be connected to standard shunt tubing sets. One version is an implantable, transcutaneously-powered/measured flow sensor module that is chronically spliced into standard shunt tubing exterior to the skull. A second version is an extracorporeal flow sensor that be connected to standard shunt and extra-ventricular drain tubing, and that can be used as a diagnostic tool during shunt revisions, or as a real-time monitoring tool to measure patient CSF flow during post-surgical recovery. These modules will measure dynamic shunt volumetric flow by sending transit-time ultrasonic pulses through the module wall. This extra-luminar design ensures that transducers never contact CSF, and that the module can be integrated with existing shunt systems. Phase-I bench/in-vivo studies validated the flow monitor's innovative concept, extraordinary flow resolution and adequate accuracy. These results will drive a Phase-II program to develop a fully implantable unit suitable for animal validation and initial clinical studies. More than 125,000 US citizens suffer from hydrocephalus - a condition demanding lifelong treatment using implanted shunt systems to drain excess cerebrospinal fluid (CSF). Shunt dysfunction is a common occurrence - with 15,000 USA inpatient admissions per year at an average cost of $28,500 per admission, at a cost of $427.5M per annum. Children are at particular risk for shunt problems, with 25-40% of first implantations failing within a year. Currently there is no objective method for quickly and easily diagnosing shunt dysfunction - and the proposed research aims to develop the first implantable shunt flow sensor that can perform this analysis in both pediatric and adult hydrocephalus patients.