Transonic Flowsensor Detects Cerebrospinal Fluid (CSF) Shunt Malfunction

Transonic Flowsensor on tubing

Hydrocephalus, derived from the Greek words hydro meaning water and cephalus meaning head, is the abnormal accumulation of cerebrospinal fluid (CSF) within the ventricles of the brain. It afflicts over 1,000,000 persons in the United States ranging from infants and older children to young, middle-aged and older adults. Hydrocephalus occurs when there is an imbalance between the amount of CSF that is produced and the rate at which it is absorbed. As the CSF builds up, it causes the ventricles to enlarge and the pressure inside the head to increase which leads to serious consequences.1

Currently, there is no way to prevent or cure hydrocephalus. The most common treatment—and the most common procedure performed by pediatric neurosurgeons in the United States—is the surgical implantation of a device called a shunt, a flexible tube that placed into the ventricular system of the brain which diverts the flow of CSF into another region of the body, most often the abdominal cavity, where it can be absorbed. A valve within the shunt maintains CSF at normal pressure within the ventricles.

However, a shunt system frequently fails or malfunctions. An estimated 50% of shunts in the pediatric population fail within two years of placement and repeated neurosurgical operations are often required. The most common shunt complication is mechanical malfunction or shunt blockage than occurs in between 8% and 64% of shunts.2 When a blockage occurs, CSF accumulates and can result in symptoms of untreated hydrocephalus. Annually, shunt malfunction accounts for roughly 39,000 admissions and as many as 433,000 hospital days for pediatric HCP alone. The annual burden for HCP-related shunts ranges from $1.4 to $2 billion per year, and nearly half of these expenses go toward the revision of malfunctioning systems.3 With the lack of any sensor that could detect a shunt malfunction immediately, the clinician would have to perform several tests that could increase radiation exposure to patients and create other complications. Moreover, the specific reason for mechanical failure—absent, excessive, or inadequate CSF flow—would often elude the clinician. 

Now there is a noninvasive, accurate Flowsensor that can detect mechanical shunt malfunction. A 2015 study, published in the Journal of Neurosurgery, evaluated an ultrasonic transit time flow sensor in five pediatric and 11 adult patients with external ventricular drains (EVDs).4 The study demonstrated that the Transonic Flowsensor accurately measures CSF output within ± 15% or ± 2 ml/hr, diagnoses the blockage or lack of flow, and records real-time continuous flow data in patients with EVDs. The authors concluded that the sensor's clinical applications may be of particular importance to the noninvasive diagnosis of shunt malfunctions with the development of an implantable device.


2Wong JM, Ziewacz JE, Ho AL, Panchmatia JR, Bader AM, Garton HJ, Laws ER, Gawande AA “Patterns in neurosurgical adverse events: cerebrospinal fluid shunt surgery,” Neurosurg Focus. 2012 Nov;33(5):E13
3Stein SC, Guo W, “Have we made progress in preventing shunt failure? A critical analysis,” J Neurosurg Pediatr. 2008 Jan;1(1):40-7.