This study compares the performance of two generations of non-invasive cerebrospinal fluid (CSF) shunt flow assessment devices. Measurements of functional implanted shunts and off-shunt locations will assess the diagnostic non-inferiority of the second-generation device to the first-generation device.

Inclusion criteria

1. A ventricular CSF shunt with a region of overlying intact skin appropriate in size for application of the study device
2. Signed informed consent by subject or a parent, legal guardian, health care agent, or surrogate decision maker (according to local statutes)
3. Signed medical records release by subject or a parent, legal guardian, health care agent, or surrogate decision maker (according to local statutes)
4. Verbal assent by minors 7 years of age and older who are able to understand the study and communicate their decision

Exclusion criteria

1. Presence of an interfering open wound or edema in the study device measurement area
2. Patient-reported history of serious adverse skin reactions to silicone-based adhesives
3. Previous participation in a Rhaeos clinical study in which FlowSense device measurement data were acquired
4. Patient or caregiver report of new or worsening symptoms of a possible shunt malfunction in the prior 7 days
5. Participation in any other investigational procedural, pharmaceutical, and/or device study that may influence the collection of valid data under this study

Pediatric and adult patients with an existing ventricular shunt will be enrolled in this study.