Implantable Multi-Modal Sensor to Improve Outcomes in Hydrocephalus Management

Abstract

Hydrocephalus is the single most common pediatric neurosurgical problem worldwide. Current treatment of this life-threatening disorder involves diverting excess fluid from the ventricles of the brain via a prosthetic shunt. While many hydrocephalus sufferers rely heavily on their ventriculo-distal shunt to maintain a healthy intracranial pressure, shunts carry a high risk of failure. Current methods of assessing shunt patency are performed within the hospital, and many patients and their families feel bound to remaining within close proximity of a hospital in order to receive timely medical intervention in the event of a shunt failure. There is a need for a system which can detect shunt malfunction, simply and reliably. We present a novel method of obtaining flow measurements from a piezoresistive pressure transducer. This builds on an earlier development of obtaining simultaneous temperature and pressure measurement from the single ultra-miniature solid-state transducer. The flow measurement system is capable of measurements in the range 0-35 ml/h, typical of the fluid flow rates through a hydrocephalus shunt. Within the flow range 0-14 ml/hour the resolution is 2 ml/hour. For flow rates greater than 16 ml/hour the resolution is 5 ml/hour. Employing a thermal flow sensing technique, the maximum heating of the local fluid is 0.65 ± 0.02°C. The flow signal is independent of ambient temperature. The sensor would be implanted in the shunt to allow the detection of the flow rate of fluid through it, enabling the clinician to measure the patency of a shunt in real time.

Multimodal Sensing Capabilities for the Detection of Shunt Failure

“…As life expectancy and demand for excellent medical healthcare increase, there is greater demand for innovative bioelectronic devices that can continuously monitor and provide reliable real-time information for an accurate diagnosis, as well as assuring correct functionality of the implantable device in different fields such as cardiovascular, pathological and neurological diseases [ 1 , 2 , 3 , 4 ]. Hydrocephalus is a neurological disorder in which there is an excess of cerebrospinal fluid (CSF) within the brain, and may develop as a consequence of trauma, infection, tumors, intracranial hemorrhage, or congenital defects.…”

An Angstrom-sensitive, differential MEMS capacitor for monitoring the milliliter dynamics of fluids

“…Our results demonstrate that our sensor is 17 times more sensitive than needed. Typically sensors intended to measure this difficult-to-measure range of flow rates and pressures in various fluids can be broken down into one of three categories: optical [19], thermal [20,21], or MEMS [22–25]. Flow sensing has also been accomplished utilizing devices that measure the fluid’s velocity via Doppler shift [26].…”

Evidence of an application of a variable MEMS capacitive sensor for detecting shunt occlusions

“…If the pressure is not found to be within this range, treatment is necessary. Clark, et al 23. have shown useful measurements of flow with a piezoresistive pressure transducer which depend on a differential in resistance, but this effective design requires an internal power source and thus the lifetime of the device is limited by the battery.…”