This study is evaluating a new, noninvasive device designed to detect whether cerebrospinal fluid (CSF) is flowing through a surgically implanted shunt. CSF shunts are commonly used to treat hydrocephalus, but it can be difficult to tell whether a shunt is working properly without invasive testing or imaging that does not directly measure flow.

The study device is a small, wireless sensor placed on the skin over the shunt tubing, typically near the collarbone. It uses gentle, controlled warmth to measure temperature changes that indicate whether fluid is flowing inside the shunt. The device does not break the skin and does not change a participant's medical care.

This study will enroll children and adults who already have a CSF shunt and who do not have new or worsening symptoms of shunt malfunction. All participants will have a measurement taken while their shunt valve is at its usual prescribed setting. Some participants with programmable shunt valves will also have a second measurement taken after their valve is temporarily adjusted to a setting intended to stop or greatly reduce flow ("virtual off"). After this measurement, the valve will be returned to its prescribed setting.

The study device results will not be shown to participants or their medical providers and will not be used to make treatment decisions. The goal of the study is to determine how well the device can distinguish between shunts that are allowing flow and those that are not.

Participants will be monitored for a short period after device use and, if applicable, after any valve adjustment. The main risks of participation are mild skin irritation from the adhesive or temporary symptoms related to valve adjustment. Participants are not expected to receive a direct medical benefit, but the information gained may help improve future diagnosis of shunt function.

This is a prospective, multicenter, open-label, blinded, observational study designed to evaluate the performance of a noninvasive wireless thermal flow detection device for assessing cerebrospinal fluid (CSF) shunt flow in pediatric and adult patients with hydrocephalus.

The study enrolls participants with an existing implanted ventricular CSF shunt who do not have new or worsening symptoms suggestive of shunt malfunction. The investigational device is placed externally on intact skin overlying the shunt tubing, typically near the clavicle, and measures thermal patterns associated with the presence or absence of CSF flow within the shunt catheter. Measurements are obtained using a sponsor-provided tablet application, and results are encoded so that both participants and treating clinicians remain blinded.

All participants undergo at least one device measurement with the shunt valve set to the participant's prescribed flow-permissive ("valve normal") setting. A subset of participants with programmable valves capable of being adjusted noninvasively will also undergo an additional measurement after the valve is temporarily adjusted to a manufacturer-reported "virtual off" setting, defined as a valve opening pressure exceeding 400 mm H₂O. After this measurement, the valve is returned to the prescribed setting, with confirmation using standard valve programming tools.

Participants whose valves are already prescribed at a "virtual off" setting will undergo a single measurement at that setting. A small number of initial roll-in participants are included to refine procedural logistics; their data are not included in the primary endpoint analyses.

The study is non-significant risk. The investigational device does not alter standard-of-care treatment, and device data are not used to guide clinical decision-making. Valve adjustments performed as part of the study are routinely used in clinical care and are monitored closely. Participants are observed for adverse events during device use and for a defined follow-up period after device removal and, when applicable, after valve readjustment.

The primary objective of the study is to assess the ability of the device to distinguish between flow-permissive and non-flowing shunts based on known valve settings. Secondary and exploratory objectives include evaluation of device accuracy metrics and characterization of thermal flow patterns under different conditions, such as posture changes or valve transitions.

Adverse events, including device-related skin findings and any symptoms associated with valve adjustment, are recorded and reported according to protocol and regulatory requirements. Participants exit the study after completion of the measurement(s) and required observation period.

Inclusion Criteria:

Inclusion and Exclusion Criteria for Roll-In Subjects Inclusion criteria

• Existing ventricular CSF shunt with an available "virtual off" setting which can be programmed noninvasively
• 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
• Signed informed consent by subject or a parent or legal guardian, health care agent, or surrogate decision maker (according to local statutes)
• Subject-reported or documented history of successful valve adjustment(s)

Inclusion and Exclusion Criteria for Main Study Subjects

Inclusion criteria

• Existing ventricular CSF shunt
• 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
• Signed informed consent by subject or a parent, legal guardian, health care agent, or surrogate decision maker (according to local statutes)

Subjects with planned "virtual off" measurement:

-Existing ventricular CSF shunt with an available "virtual off" setting which can be programmed noninvasively

Subjects with planned adjustment to the "virtual off" setting only:

-Subject-reported or documented history of successful valve adjustment(s)

Exclusion Criteria:

Exclusion criteria

• Presence of more than one distal shunt catheter in the study device measurement region
• Presence of an interfering open wound or edema in the study device measurement region
• Shunt is difficult to palpate, or the shunt depth at the device measurement location is deeper than 5 mm from the skin surface via ultrasound measurement
• Shunt valve is set to an opening pressure of >= 300 mm H2O, or the shunt system is otherwise set to substantially prevent shunt flow (e.g. Certas Plus valve programmed to a setting of 8 or a ligated shunt)
• Investigator judges that the subject is likely to be shunt independent (e.g. does not require a functional shunt for management of hydrocephalus)
• Subject has more than one intact and presumed functional distal catheter
• Subject-reported or documented history of serious adverse skin reactions to silicone-based adhesives
• Subject-reported new or worsening symptoms of a possible shunt malfunction in the prior 7 days
• 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
• Prior enrollment in this study
• Participation in any other investigational procedural, pharmaceutical, and/or device study that may influence the collection of valid data under this study

Exclusion Criteria for Main Study Subjects Exclusion criteria

• Presence of more than one distal shunt catheter in the study device measurement region
• Presence of an interfering open wound or edema in the study device measurement region
• Shunt is difficult to palpate, or the shunt depth at the device measurement location is deeper than 5 mm from the skin surface via ultrasound measurement
• Subject-reported or documented history of serious adverse skin reactions to silicone-based adhesives
• Subject-reported new or worsening symptoms of a possible shunt malfunction in the prior 7 days
• 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
• Prior enrollment in this study
• Participation in any other investigational procedural, pharmaceutical, and/or device study that may influence the collection of valid data under this study
• Previous participation in a Rhaeos clinical study in which the study device (current generation) was used to acquire measurement data

Subjects with planned "valve normal" measurements:

• Shunt system is set to substantially prevent shunt flow (e.g. ligated shunt)
• Investigator judges that the subject is likely to be shunt independent (e.g. does not require a functional shunt for management of hydrocephalus)
• Subject has more than one intact and presumed functional distal catheter