Study of Shunt Flow Under Different Valve Settings Using a Wireless Sensor

A Prospective Study Comparing CSF Shunt Flow Between "Virtual Off" and "Flow-Permissive" Shunt Valve Settings Using a Wireless, Noninvasive Shunt Flow Sensor

Hydrocephalus is commonly treated with a cerebrospinal fluid (CSF) shunt, a device that drains excess fluid from the brain. However, shunts can stop working over time, and determining whether fluid is flowing through a shunt can be difficult. Current diagnostic methods may require imaging studies or invasive procedures, which can be time-consuming, costly, or uncomfortable for patients.

The purpose of this study is to evaluate the performance of the Rhaeos Shunt Monitoring System (RSMS), an investigational wireless, noninvasive device designed to detect flow in implanted CSF shunts. The study will compare RSMS directly with ShuntCheck III, an FDA-cleared noninvasive device that is also used to assess CSF shunt flow. Both devices are placed on the skin over the shunt and use thermal sensing technology to evaluate whether fluid is flowing through the shunt.

Approximately 85 pediatric and adult participants with an existing ventricular CSF shunt will be enrolled. Participants must have a functioning shunt and no recent symptoms suggesting shunt malfunction. Some participants with programmable shunt valves will have their valve temporarily adjusted to a manufacturer-provided "virtual off" setting, which is intended to substantially restrict shunt flow. These participants may also undergo measurements at their normal valve setting. Other participants will only undergo measurements at their normal valve setting.

During the study visit, participants will undergo shunt flow assessments with both RSMS and ShuntCheck III. The order in which the devices are used will be randomized. Device measurements are collected while participants are seated upright, and participants and their treating clinicians will remain blinded to the measurement results. The study devices will not be used to make treatment decisions, and participation will not alter standard medical care. Adverse events associated with device use or valve adjustments will be monitored and recorded.

The primary goal of the study is to compare the ability of RSMS and ShuntCheck III to correctly identify shunts with flow-permissive ("valve normal") and restricted-flow ("virtual off") settings. Results from this study may help support the future development of a noninvasive tool to aid neurosurgeons in assessing CSF shunt flow. Participants are not expected to receive a direct medical benefit from taking part in the study.

Hydrocephalus is commonly treated with surgically implanted cerebrospinal fluid (CSF) shunts that divert excess CSF from the brain to another part of the body. Shunt malfunction is a frequent complication of treatment and can result in significant morbidity if not identified and treated promptly. However, diagnosis of shunt malfunction remains challenging because patient symptoms are often nonspecific and currently available diagnostic tools have important limitations. Existing noninvasive assessments generally rely on indirect indicators of shunt function, while invasive procedures may expose patients to discomfort, infection risk, or other complications.

The Rhaeos Shunt Monitoring System (RSMS) is an investigational, wireless, noninvasive device designed to aid in the detection of flow in implanted CSF shunts. RSMS uses thermal sensing technology to evaluate CSF flow through shunt tubing by measuring temperature changes associated with fluid movement. The device is placed on the skin overlying a palpable shunt segment, typically near the clavicle, and communicates wirelessly with a tablet application to perform measurements and record results.

This study is a prospective, multicenter, open-label, blinded, observational study designed to compare the performance of RSMS with ShuntCheck III, an FDA-cleared noninvasive device indicated as an aid to the detection of flow in implanted CSF shunts. Both devices use transcutaneous thermal sensing methods to assess shunt flow, but they differ in implementation. RSMS uses a controlled heating element and wireless electronics, while ShuntCheck III uses a disposable thermosensor and cooling from an instant cold pack.

Approximately 85 pediatric and adult participants with existing ventricular CSF shunts will be enrolled. Eligible participants must have a palpable shunt segment suitable for device placement and must not have recent symptoms suggestive of shunt malfunction.

Participants with programmable shunt valves capable of being adjusted to a manufacturer-defined "virtual off" setting (opening pressure greater than 400 mm H₂O) will undergo device assessments after the valve has been adjusted to the virtual off setting. These participants may also undergo optional measurements at their prescribed flow-permissive ("valve normal") setting prior to valve adjustment. Participants whose valves are not adjusted will undergo measurements only at their prescribed valve setting. For each assessment, the order of RSMS and ShuntCheck III testing will be randomized. Participants and treating clinicians will remain blinded to device outputs throughout the study.

The primary objective of the study is to compare the sensitivity and specificity of RSMS and ShuntCheck III for detecting flow-restricted and flow-permissive shunt conditions. Device performance will be evaluated using the known valve setting as the reference condition. Measurements obtained while the valve is set to the virtual off setting will serve as flow-restricted conditions, while measurements obtained at valve-normal settings will serve as flow-permissive conditions.

Secondary analyses will evaluate additional performance characteristics, including accuracy, positive predictive value, negative predictive value, receiver operating characteristic (ROC) curve analysis, measurement completion rates, and the number of measurement attempts required to obtain a successful result. Exploratory analyses will assess device performance across clinical and demographic subgroups and study-specific variables such as body position, shunt depth, valve setting, and study site.

All study procedures are conducted in conjunction with standard clinical care. Device measurements are used solely for research purposes and will not be available to treating clinicians for patient management decisions. Participants undergoing temporary valve adjustment will be monitored following restoration of their prescribed valve setting, and all participants will be monitored for adverse events associated with device use. Adverse events, device deficiencies, and protocol deviations will be documented throughout the study.

The results of this study are intended to provide clinical evidence regarding the performance of a next-generation, wireless, noninvasive shunt flow monitoring technology and to support future regulatory evaluation of the RSMS device.

Inclusion Criteria:

Existing ventricular cerebrospinal fluid (CSF) shunt. Region of intact skin overlying an unambiguously identifiable, palpable, chronically indwelling ventricular shunt crossing the clavicle and appropriate in size for application of the study device.

Written informed consent provided by the participant or, when applicable, by a parent, legal guardian, health care agent, or surrogate decision maker according to local regulations.

For participants with planned "virtual off" measurements:

Existing ventricular CSF shunt with a programmable valve that has an available manufacturer-reported "virtual off" setting and can be programmed noninvasively.

For participants whose valve will be adjusted to the "virtual off" setting during the study:

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

Exclusion Criteria:

Presence of more than one distal shunt catheter in the study device measurement region.

Presence of an open wound or edema in the study device measurement region that would interfere with device placement.

Shunt difficult to palpate or shunt depth greater than 5 mm from the skin surface at the measurement location as determined by ultrasound.

Subject-reported or documented history of serious adverse skin reactions to silicone-based adhesives.

New or worsening symptoms suggestive of shunt malfunction within the previous 7 days.

Use of the study device would interfere with standard patient care, emergency surgery cannot be delayed, or study participation would interfere with optimal medical care.

Participation in another investigational procedural, pharmaceutical, or device study that may affect data collected in this study.

Previous participation in a Rhaeos clinical study using the current-generation RH05-B1 study device.

For participants with planned "valve normal" measurements only:

Investigator judges the participant is likely to be shunt independent (e.g., does not require a functional shunt for management of hydrocephalus).

This format follows ClinicalTrials.gov conventions by separating general criteria from those that apply only to specific participant subgroups.