This study evaluates the performance of the study device, FlowSense®, a sensor for non-invasively assessing cerebrospinal fluid (CSF) shunt flow. Subjects with an existing implanted ventricular CSF shunt will be evaluated with the study device in an outpatient setting to determine the negative predictive value (NPV; Part 1, blinded) and explore changes in surveillance imaging, health resource utilization, and visit duration during routine follow-up visits (Part 2, unblinded).

Inclusion criteria

1. Existing ventricular cerebrospinal fluid shunt
2. Age ≥ 2 years old
3. Region of intact skin overlying an unambiguously identifiable palpable chronically indwelling ventricular shunt that crosses the clavicle; region of skin is appropriate in size for application of the study device
4. Capable of providing informed consent or have a legal guardian, health care agent, or surrogate decision-maker able to provide informed consent
5. Standard of care outpatient visit with neurosurgeon assessment of having "no clinical concern for shunt malfunction"

Exclusion criteria

1. Subject not scheduled to receive outpatient standard of care imaging (CT, MRI, X-ray shunt series) as part of the clinic visit
2. Presence of more than one distal shunt catheter in the study device measurement region
3. Presence of an interfering open wound or edema in the study device measurement region
4. Subject-reported history of adverse skin reactions to silicone adhesives
5. Participation in the study will interfere with, or be detrimental to, the administration of optimal health care to the subject
6. Subject not available for seven-day follow-up