An exploratory "Fit & Function" study of Continuous Real Time (CRT) ShuntCheck, a non-invasive method for monitoring changes in cerebrospinal fluid (CSF) shunt flow in hydrocephalus patients. The device will be tested on 10 pediatric patients (at Johns Hopkins Hospital) and 10 adult patients (at LifeBridge Health) and results will be used to optimize device design.

An exploratory "Fit & Function" study of Continuous Real Time (CRT) ShuntCheck, a non-invasive method for monitoring changes in CSF shunt flow in hydrocephalus patients. This study will gather information to refine the design of the CRT ShuntCheck sensor. Our Aim I product work will yield a clinic-ready prototype which adheres well to human skin, conforms to the curve surface of the clavicle and provides a safe level of skin cooling over an extended period of time. Many of the clinical uses of CRT will involve patient movement - standing up to investigate suspected overdrainage, or the simple fidgeting of children undergoing monitoring. The Aim II Fit and Function testing will most importantly identify movement-related product performance issues. If we can identify the causes of "signal noise", we can modify our sensor design to make it less susceptible to "motion artifacts".

Additionally testing will identify age/size specific issues - is the sensor small enough for use on younger children, does the looser skin of older adults generate move motion artifacts in the signal.

These studies will include 10 pediatric and 10 adult asymptomatic patients who are willing to undergo CRT ShuntCheck testing over a one hour period. Test results will not be used to guide patient care and testing will not interfere with or delay any other patient testing or care.

Inclusion Criteria:

1. For the pediatric subjects, males or females, older than three and less than 20 years of age.
2. For the adult subjects, males or females, older than 35 years of age
3. Parent/guardian or alert subject (age 18 or over) capable of giving consent; subject less than 18 and of assent age must give assent to participate if appropriate and required by the institution. If the subjects are incapable of giving assent, then only parent/guardian consent is required.
4. Possess an unambiguously identifiable chronically indwelling ventricular shunt which crosses the clavicle.

Exclusion Criteria:

1. Inability or unwillingness of the parent/guardian or alert subject to give informed consent/assent (when appropriate) as required by the Institutional Review Board.
2. Study testing would interfere with emergent subject care or if the subject is scheduled to go the OR in short order.
3. Presence of an interfering open wound or edema over the shunt.