Continuous, noninvasive wireless monitoring of flow of cerebrospinal fluid through shunts in patients with hydrocephalus

Low-Cost Photoelectric Flow Rate Sensors Based on a Flexible Planar Curved Beam Structure for Clinical Treatments

In clinical treatments, reliable flow rate measurements ensure accurate drug delivery during infusions, precise gas delivery during artificial ventilations, etc., thereby reducing patient morbidity and mortality. However, precise flow rate sensors are costly, so medical devices with limited budgets choose cheaper but unsatisfactory flow rate measurement approaches, leading to increased medical risks. Here, a photoelectric flow rate sensor based on a flexible planar curved beam structure (FPCBS) is proposed. The FPCBS ensures low out-of-plane stiffness of the sensitive sheet and allows large deformation in the elastic range, enabling the flow rate sensor to measure the flow rate with high sensitivity over a wide range. Meanwhile, the flow rate sensor can be mass-produced using mature materials and manufacturing technology at less than $5 each. The flow rate sensors are integrated into a commercial infusion pump to measure drug infusion and a home ventilator to monitor respiration. The results are comparable to those measured by a commercial flow rate sensor, demonstrating the applicability of the sensor. Considering its proven outstanding performance at low cost, the flow rate sensor shows great potential in clinical treatment, medical diagnosis, and other medical fields.

Advancements in Cerebrospinal Fluid Biosensors: Bridging the Gap from Early Diagnosis to the Detection of Rare Diseases

Cerebrospinal fluid (CSF) is a body fluid that can be used for the diagnosis of various diseases. However, CSF collection requires an invasive and painful procedure called a lumbar puncture (LP). This procedure is applied to any patient with a known risk of central nervous system (CNS) damage or neurodegenerative disease, regardless of their age range. Hence, this can be a very painful procedure, especially in infants and elderly patients. On the other hand, the detection of disease biomarkers in CSF makes diagnoses as accurate as possible. This review aims to explore novel electrochemical biosensing platforms that have impacted biomedical science. Biosensors have emerged as techniques to accelerate the detection of known biomarkers in body fluids such as CSF. Biosensors can be designed and modified in various ways and shapes according to their ultimate applications to detect and quantify biomarkers of interest. This process can also significantly influence the detection and diagnosis of CSF. Hence, it is important to understand the role of this technology in the rapidly progressing field of biomedical science.

Quantitative noninvasive measurement of cerebrospinal fluid flow in shunted hydrocephalus

OBJECTIVE

Standard MRI protocols lack a quantitative sequence that can be used to evaluate shunt-treated patients with a history of hydrocephalus. The objective of this study was to investigate the use of phase-contrast MRI (PC-MRI), a quantitative MR sequence, to measure CSF flow through the shunt and demonstrate PC-MRI as a useful adjunct in the clinical monitoring of shunt-treated patients.

METHODS

The rapid (96 seconds) PC-MRI sequence was calibrated using a flow phantom with known flow rates ranging from 0 to 24 mL/hr. Following phantom calibration, 21 patients were scanned with the PC-MRI sequence. Multiple, successive proximal and distal measurements were gathered in 5 patients to test for measurement error in different portions of the shunt system and to determine intrapatient CSF flow variability. The study also includes the first in vivo validations of PC-MRI for CSF shunt flow by comparing phase-contrast-measured flow rate with CSF accumulation in a collection burette obtained in patients with externalized distal shunts.

RESULTS

The PC-MRI sequence successfully measured CSF flow rates ranging from 6 to 54 mL/hr in 21 consecutive pediatric patients. Comparison of PC-MRI flow measurement and CSF volume collected in a bedside burette showed good agreement in a patient with an externalized distal shunt. Notably, the distal portion of the shunt demonstrated lower measurement error when compared with PC-MRI measurements acquired in the proximal catheter.

CONCLUSIONS

The PC-MRI sequence provided accurate and reliable clinical measurements of CSF flow in shunt-treated patients. This work provides the necessary framework to include PC-MRI as an immediate addition to the clinical setting in the noninvasive evaluation of shunt function and in future clinical investigations of CSF physiology.

A novel ventriculoperitoneal shunt flow sensor based on electrically induced spatial variation in cerebrospinal fluid charge density

Introduction: Ventriculoperitoneal (VP) shunts divert cerebrospinal fluid (CSF) out of cerebral ventricles in patients with hydrocephalus or elevated intracranial pressure (ICP). Despite high failure rates, there exist limited clinically viable solutions for long-term and continuous outpatient monitoring of CSF flow rate through VP shunts. We present a novel, low-power method for sensing analog CSF flow rate through a VP shunt premised on induced spatial electrical charge variation. Methods: Two geometric variants of the proposed sensing mechanism were prototyped: linear wire (P1) and cylindrical (P2) electrodes. Normal saline was gravity-driven through P1 and a commercially available shunt system in series. True flow rates were measured using a high-precision analytical balance. Subsequently, artificial CSF was driven by a programmable syringe pump through P2. Flow rate prediction models were empirically derived and tested. Sensor response was also assessed during simulated obstruction trials. Finally, power consumption per flow measurement was measured. Results: P1 (17 mm long) and P2 (22 mm long) averaged 7.2% and 4.2% error, respectively, in flow rate measurement from 0.01 to 0.90 mL/min. Response curves exhibited an appreciably flattened profile during obstruction trials compared to non-obstructed states. P2 consumed 37.5 µJoules per flow measurement. Conclusion: We propose a novel method for accurately sensing CSF flow rate through a VP shunt and validate this method at the benchtop with normal saline and artificial CSF over a board range of flows (0.01-0.90 mL/min). The sensing element is highly power efficient, compact, insertable into existing shunt and valve assemblies, and does not alter CSF flow mechanics.

SmartWear body sensors for neurological and neurosurgical patients: A review of current and future technologies

Background/objective

Recent technological advances have allowed for the development of smart wearable devices (SmartWear) which can be used to monitor various aspects of patient healthcare. These devices provide clinicians with continuous biometric data collection for patients in both inpatient and outpatient settings. Although these devices have been widely used in fields such as cardiology and orthopedics, their use in the field of neurosurgery and neurology remains in its infancy.

Methods

A comprehensive literature search for the current and future applications of SmartWear devices in the above conditions was conducted, focusing on outpatient monitoring.

Findings

Through the integration of sensors which measure parameters such as physical activity, hemodynamic variables, and electrical conductivity - these devices have been applied to patient populations such as those at risk for stroke, suffering from epilepsy, with neurodegenerative disease, with spinal cord injury and/or recovering from neurosurgical procedures. Further, these devices are being tested in various clinical trials and there is a demonstrated interest in the development of new technologies.

Conclusion

This review provides an in-depth evaluation of the use of SmartWear in selected neurological diseases and neurosurgical applications. It is clear that these devices have demonstrated efficacy in a variety of neurological and neurosurgical applications, however challenges such as data privacy and management must be addressed.

Current state of the art and future directions for implantable sensors in medical technology: Clinical needs and engineering challenges

Implantable sensors have revolutionized the way we monitor biophysical and biochemical parameters by enabling real-time closed-loop intervention or therapy. These technologies align with the new era of healthcare known as healthcare 5.0, which encompasses smart disease control and detection, virtual care, intelligent health management, smart monitoring, and decision-making. This review explores the diverse biomedical applications of implantable temperature, mechanical, electrophysiological, optical, and electrochemical sensors. We delve into the engineering principles that serve as the foundation for their development. We also address the challenges faced by researchers and designers in bridging the gap between implantable sensor research and their clinical adoption by emphasizing the importance of careful consideration of clinical requirements and engineering challenges. We highlight the need for future research to explore issues such as long-term performance, biocompatibility, and power sources, as well as the potential for implantable sensors to transform healthcare across multiple disciplines. It is evident that implantable sensors have immense potential in the field of medical technology. However, the gap between research and clinical adoption remains wide, and there are still major obstacles to overcome before they can become a widely adopted part of medical practice.

Implantable Intracranial Pressure Sensor with Continuous Bluetooth Transmission via Mobile Application

Hydrocephalus is a clinical disorder caused by excessive cerebrospinal fluid (CSF) buildup in the ventricles of the brain, often requiring permanent CSF diversion via an implanted shunt system. Such shunts are prone to failure over time; an ambulatory intracranial pressure (ICP) monitoring device may assist in the detection of shunt failure without an invasive diagnostic workup. Additionally, high resolution, noninvasive intracranial pressure monitoring will help in the study of diseases such as normal pressure hydrocephalus (NPH) and idiopathic intracranial hypertension (IIH). We propose an implantable, continuous, rechargeable ICP monitoring device that communicates via Bluetooth with mobile applications. The design requirements were met at the lower ICP ranges; the obtained error fell within the idealized ±2 mmHg margin when obtaining pressure values at or below 20 mmHg. The error was slightly above the specified range at higher ICPs (±10% from 20-100 mmHg). The system successfully simulates occlusions and disconnections of the proximal and distal catheters, valve failure, and simulation of A and B ICP waves. The mobile application accurately detects the ICP fluctuations that occur in these physiologic states. The presented macro-scale prototype is an ex-vivo model of an implantable, rechargeable ICP monitoring system that has the potential to measure clinically relevant ICPs and wirelessly provide accessible and continuous data to aid in the workup of shunt failure.

Intramuscular Microvascular Flow Sensing for Flap Monitoring in a Porcine Model of Arterial and Venous Occlusion

BACKGROUND

 Commercially available near infrared spectroscopy devices for continuous free flap tissue oxygenation (StO₂) monitoring can only be used on flaps with a cutaneous component. Additionally, differences in skin quality and pigmentation may alter StO₂ measurements. Here, we present a novel implantable heat convection probe that measures microvascular blood flow for peripheral monitoring of free flaps, and is not subject to the same issues that limit the clinical utility of near-infrared spectroscopy.

METHODS

 The intratissue microvascular flow-sensing device includes a resistive heater, 4 thermistors, a small battery, and a Bluetooth chip, which allows connection to a smart device. Convection of applied heat is measured and mathematically transformed into a measurement of blood flow velocity. This was tested alongside Vioptix T.Ox in a porcine rectus abdominis myocutaneous flap model of arterial and venous occlusion. After flap elevation, the thermal device was deployed intramuscularly, and the cutaneous T.Ox device was applied. Acland clamps were alternately applied to the flap artery and veins to achieve 15 minutes periods of flap ischemia and congestion with a 15 minutes intervening recovery period. In total, five devices were tested in three flaps in three separate pigs over 16 vaso-occlusive events.

RESULTS

 Flow measurements were responsive to both ischemia and congestion, and returned to baseline during recovery periods. Flow measurements corresponded closely with measured StO_2. Cross-correlation at zero lag showed agreement between these two sensing modalities. Two novel devices tested simultaneously on the same flap showed only minor variations in flow measurements.

CONCLUSION

 This novel probe is capable of detecting changes in tissue microcirculatory blood flow. This device performed well in a swine model of flap ischemia and congestion, and shows promise as a potentially useful clinical tool. Future studies will investigate performance in fasciocutaneous flaps and characterize longevity of the device over a period of several days.

Advanced thermal sensing techniques for characterizing the physical properties of skin

Measurements of the thermal properties of the skin can serve as the basis for a noninvasive, quantitative characterization of dermatological health and physiological status. Applications range from the detection of subtle spatiotemporal changes in skin temperature associated with thermoregulatory processes, to the evaluation of depth-dependent compositional properties and hydration levels, to the assessment of various features of microvascular/macrovascular blood flow. Examples of recent advances for performing such measurements include thin, skin-interfaced systems that enable continuous, real-time monitoring of the intrinsic thermal properties of the skin beyond its superficial layers, with a path to reliable, inexpensive instruments that offer potential for widespread use as diagnostic tools in clinical settings or in the home. This paper reviews the foundational aspects of the latest thermal sensing techniques with applicability to the skin, summarizes the various devices that exploit these concepts, and provides an overview of specific areas of application in the context of skin health. A concluding section presents an outlook on the challenges and prospects for research in this field.

Translational gaps and opportunities for medical wearables in digital health

A confluence of advances in biosensor technologies, enhancements in health care delivery mechanisms, and improvements in machine learning, together with an increased awareness of remote patient monitoring, has accelerated the impact of digital health across nearly every medical discipline. Medical grade wearables-noninvasive, on-body sensors operating with clinical accuracy-will play an increasingly central role in medicine by providing continuous, cost-effective measurement and interpretation of physiological data relevant to patient status and disease trajectory, both inside and outside of established health care settings. Here, we review current digital health technologies and highlight critical gaps to clinical translation and adoption.

Utilizing Data from Wearable Technologies in the Era of Telemedicine to Assess Patient Function and Outcomes in Neurosurgery: Systematic Review and Time-Trend Analysis of the Literature

BACKGROUND

The COVID-19 pandemic has driven the increased use of telemedicine and the adoption of wearable technology in neurosurgery. We reviewed studies exploring the use of wearables on neurosurgical patients and analyzed wearables' scientific production trends.

METHODS

The review encompassed PubMed, EMBASE, Web of Science, and Cochrane Library. Bibliometric analysis was performed using citation data of the included studies through Elsevier's Scopus database. Linear regression was utilized to understand scientific production trends. All analyses were performed on R 4.1.2.

RESULTS

We identified 979 studies. After screening, 49 studies were included. Most studies evaluated wearable technology use for patients with spinal pathology (n = 31). The studies were published over a 24-year period (1998-2021). Forty-seven studies involved wearable device use relevant to telemedicine. Bibliometric analysis revealed a compounded annual growth rate of 7.3%, adjusted for inflation, in annual scientific production from 1998 to 2021 (coefficient=1.3; 95% Confidence Interval = [0.7, 1.9], P < 0.01). Scientific production steadily increased in 2014 (n = 1) and peaked from 2019 (n = 8) to 2021 (n = 13) in correlation with the COVID-19 pandemic. Publications spanned 34 journals, averaged 24.4 citations per article, 3.0 citations per year per article, and 8.3 authors per article.

CONCLUSION

Wearables can provide clinicians with objective measurements to determine patient function and quality of life. The rise in articles related to wearables in neurosurgery demonstrates the increased adoption of wearable devices during the COVID-19 pandemic. Wearable devices appear to be a key component in this era of telemedicine and their positive utility and practicality are increasingly being realized in neurosurgery.

PEDOT Composite with Ionic Liquid and Its Application to Deformable Electrochemical Transistors

Organic electrochemical transistors (OECTs) have become popular due to their advantages of a lower operating voltage and higher transconductance compared with conventional silicon transistors. However, current OECT platform-based skin-inspired electronics applications are limited due to the lack of stretchability in poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS). Some meaningful structural design strategies to resolve this limitation, including rendering OECT to make it more stretchable, have been reported. However, these strategies require complicated fabrication processes and face challenges due to the low areal density of active devices because wavy interconnect parts account for a large area. Nevertheless, there have been only a few reports of fully deformable OECT having skin-like mechanical properties and deformability. In this study, we fabricated stretchable and conductivity-enhanced channel materials using a spray-coating method after a composite solution preparation by blending PEDOT:PSS with several ionic liquids. Among these, the PEDOT composite prepared using 1-butyl-3-methylimidazolium octyl sulfate exhibited a better maximum transconductance value (~0.3 mS) than the other ion composites. When this material was used for our deformable OECT platform using stretchable Au nanomembrane electrodes on an elastomer substrate and an encapsulation layer, our d-ECT showed a barely degraded resistance value between the source and drain during 1000 cycles of a 30% repeated strain. We expect that our d-ECT device will serve as a step toward the development of more precise and accurate biomedical healthcare monitoring systems.

Optimization of a Thermal Flow Meter for Failure Management of the Shunt in Pediatric Hydrocephalus Patients. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2021;2021:1551-1556. [PMID: 34891580 DOI: 10.1109/embc46164.2021.9630302] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

Hydrocephalus patients suffer from an abnormal buildup of cerebrospinal fluid (CSF) in their ventricles, and there is currently no known way to cure hydrocephalus. The most prevalent treatment for managing hydrocephalus is to implant a ventriculoperitoneal shunt, which diverts excess CSF out of the brain. However, shunts are prone to failure, resulting in vague symptoms. Our patient survey results found that the lack of specificity of symptoms complicates the management of hydrocephalus in the pediatric population. The consequences include persistent mental burden on caretakers and a significant amount of unnecessary utilization of emergency healthcare resources due to the false-positive judgement of shunt failure. In order to reliably monitor shunt failures for hydrocephalus patients and their caretakers, we propose an optimized design of the thermal flow meter for precise measurements of the CSF flow rate in the shunt. The design is an implantable device which slides onto the shunt and utilizes sinusoidal heating and temperature measurements to improve the signal-to-noise ratio of flow-rate measurements by orders of magnitude.Clinical Relevance- An implantable flow meter would be transformative to allow hydrocephalus patients to monitor their shunt function at home, resulting in reduced hospital visits, reduced exposure to radiation typically required to rule out shunt failure, and reduced caretaker anxiety.

Wireless Power Transfer and Telemetry for Implantable Bioelectronics

Implantable bioelectronic devices are becoming useful and prospective solutions for various diseases owing to their ability to monitor or manipulate body functions. However, conventional implantable devices (e.g., pacemaker and neurostimulator) are still bulky and rigid, which is mostly due to the energy storage component. In addition to mechanical mismatch between the bulky and rigid implantable device and the soft human tissue, another significant drawback is that the entire device should be surgically replaced once the initially stored energy is exhausted. Besides, retrieving physiological information across a closed epidermis is a tricky procedure. However, wireless interfaces for power and data transfer utilizing radio frequency (RF) microwave offer a promising solution for resolving such issues. While the RF interfacing devices for power and data transfer are extensively investigated and developed using conventional electronics, their application to implantable bioelectronics is still a challenge owing to the constraints and requirements of in vivo environments, such as mechanical softness, small module size, tissue attenuation, and biocompatibility. This work elucidates the recent advances in RF-based power transfer and telemetry for implantable bioelectronics to tackle such challenges.

United States Medicolegal Progress and Innovation in Telemedicine in the Age of COVID-19: A Primer for Neurosurgeons

Telemedicine has received increased attention in recent years as a potential solution to expand clinical capability and patient access to care in many fields, including neurosurgery. Although patient and physician attitudes are rapidly shifting toward greater telemedicine use in light of the COVID-19 pandemic, there remains uncertainty about telemedicine's regulatory future. Despite growing evidence of telemedicine's utility, there remain a number of significant medicolegal barriers to its mass adoption and wider implementation. Herein, we examine recent progress in state and federal regulations in the United States governing telemedicine's implementation in quality of care, finance and billing, privacy and confidentiality, risk and liability, and geography and interstate licensure, with special attention to how these concern teleneurosurgical practice. We also review contemporary topics germane to the future of teleneurosurgery, including the continued expansion of reciprocity in interstate licensure, expanded coverage for homecare services for chronic conditions, expansion of Center for Medicare and Medicaid Services reimbursements, and protections of store-and-forward technologies. Additionally, we discuss recent successes in teleneurosurgery, stroke care, and rehabilitation as models for teleneurosurgical best practices. As telemedicine technology continues to mature and its expanse grows, neurosurgeons' familiarity with its benefits, limitations, and controversies will best allow for its successful adoption in our field to maximize patient care and outcomes.

Craniosacral Therapy Use in Normal Pressure Hydrocephalus

Nearly 700,000 adults in the US have normal pressure hydrocephalus (NPH), but it is often misdiagnosed as Alzheimer’s or Parkinson’s disease. In fact, a small percentage of people with the disease are properly diagnosed. NPH presents classically with a triad of symptoms: ataxic gait, dementia, and urinary incontinence. Diagnosis and treatment are provided together through a lumbar puncture. However, the only effective treatment that exists is a shunt insertion, which is a highly invasive procedure with uncertain responsiveness. As NPH is primarily diagnosed in those in advanced ages (60s and 70s), adjunctive treatment modalities should be further studied. Here we present a case of a patient diagnosed by a neurosurgeon and neurologist with NPH and a candidate for a shunt insertion whose symptoms substantially improved with one month of osteopathic manipulative treatment. Osteopathic considerations and literature are also reviewed in the broader context of craniosacral treatment.

Cohabiting Plant-Wearable Sensor In Situ Monitors Water Transport in Plant

The boom of plant phenotype highlights the need to measure the physiological characteristics of an individual plant. However, continuous real-time monitoring of a plant's internal physiological status remains challenging using traditional silicon-based sensor technology, due to the fundamental mismatch between rigid sensors and soft and curved plant surfaces. Here, the first flexible electronic sensing device is reported that can harmlessly cohabitate with the plant and continuously monitor its stem sap flow, a critical plant physiological characteristic for analyzing plant health, water consumption, and nutrient distribution. Due to a special design and the materials chosen, the realized plant-wearable sensor is thin, soft, lightweight, air/water/light-permeable, and shows excellent biocompatibility, therefore enabling the sap flow detection in a continuous and non-destructive manner. The sensor can serve as a noninvasive, high-throughput, low-cost toolbox, and holds excellent potentials in phenotyping. Furthermore, the real-time investigation on stem flow insides watermelon reveals a previously unknown day/night shift pattern of water allocation between fruit and its adjacent branch, which has not been reported before.

Wireless and battery-free platforms for collection of biosignals

Recent progress in biosensors have quantitively expanded current capabilities in exploratory research tools, diagnostics and therapeutics. This rapid pace in sensor development has been accentuated by vast improvements in data analysis methods in the form of machine learning and artificial intelligence that, together, promise fantastic opportunities in chronic sensing of biosignals to enable preventative screening, automated diagnosis, and tools for personalized treatment strategies. At the same time, the importance of widely accessible personal monitoring has become evident by recent events such as the COVID-19 pandemic. Progress in fully integrated and chronic sensing solutions is therefore increasingly important. Chronic operation, however, is not truly possible with tethered approaches or bulky, battery-powered systems that require frequent user interaction. A solution for this integration challenge is offered by wireless and battery-free platforms that enable continuous collection of biosignals. This review summarizes current approaches to realize such device architectures and discusses their building blocks. Specifically, power supplies, wireless communication methods and compatible sensing modalities in the context of most prevalent implementations in target organ systems. Additionally, we highlight examples of current embodiments that quantitively expand sensing capabilities because of their use of wireless and battery-free architectures.

Multimodal Sensing Capabilities for the Detection of Shunt Failure

Hydrocephalus is a medical condition characterized by the abnormal accumulation of cerebrospinal fluid (CSF) within the cavities of the brain called ventricles. It frequently follows pediatric and adult congenital malformations, stroke, meningitis, aneurysmal rupture, brain tumors, and traumatic brain injury. CSF diversion devices, or shunts, have become the primary therapy for hydrocephalus treatment for nearly 60 years. However, routine treatment complications associated with a shunt device are infection, obstruction, and over drainage. Although some (regrettably, the minority) patients with shunts can go for years without complications, even those lucky few may potentially experience one shunt malfunction; a shunt complication can require emergency intervention. Here, we present a soft, wireless device that monitors distal terminal fluid flow and transmits measurements to a smartphone via a low-power Bluetooth communication when requested. The proposed multimodal sensing device enabled by flow sensors, for measurements of flow rate and electrodes for measurements of resistance in a fluidic chamber, allows precision measurement of CSF flow rate over a long time and under any circumstances caused by unexpected or abnormal events. A universal design compatible with any modern commercial spinal fluid shunt system would enable the widespread use of this technology.