This study evaluates the performance of a device for non-invasively assessing cerebrospinal fluid (CSF) shunt flow over multiple measurements performed by a study subject during headache and non-headache periods.

Inclusion Criteria:

1. Existing ventriculoperitoneal CSF shunt
2. Subject experiencing ongoing headaches including at least 15 headache days per month for the past 3 months
3. Region of intact skin overlying an unambiguously identifiable palpable chronically indwelling ventricular shunt which crosses the clavicle and is appropriate in size for application of the study device
4. Available for remote and in-person follow-up during the 30-day measurement period
5. Signed informed consent by subject or a parent, legal guardian, health care agent, or surrogate decision maker (according to local statutes)
6. Subject or caregiver is able to clearly communicate and document information and shunt symptoms in English
7. Subject is at least 6 years old but not more than 80 years old

Exclusion Criteria:

1. Presence of more than one distal shunt catheter in the study device measurement region
2. Shunt is not palpable due to depth or depth of shunt where the device will be placed is greater than 4 mm per ultrasound evaluation
3. Presence of an interfering open wound or edema in the study device measurement region
4. Subject-reported history of serious adverse skin reactions to silicone-based adhesives
5. Investigator judges that the subject is likely to be lost to follow-up due to unavailability or clinical outcome being unobtainable
6. Investigator judges that the subject is unlikely to successfully take reliable measurements at home
7. Investigator judges that the subject/subject's caretaker would not be able to successfully place the device without assistance
8. Use of the study device would interfere with standard patient care, or emergency surgery that cannot be delayed, or participation in the study will interfere with, or be detrimental to, administration of optimal healthcare to the subject
9. Prior enrollment in this study
10. Participation in any other investigational procedural, pharmaceutical, and/or device study that may influence the collection of valid data under this study