Noninvasive Intracranial Pressure Monitoring Research Articles

Using EEG total energy as a noninvasively tracking of intracranial (and cerebral perfussion) pressure in an animal model: A pilot study

Purpose: This study aims to describe the total EEG energy during episodes of intracranial hypertension (IH) and evaluate its potential as a classification feature for IH. New methods: We computed the sample correlation coefficient between intracranial pressure (ICP) and the total EEG energy. Additionally, a generalized additive model was employed to assess the relationship between arterial blood pressure (ABP), total EEG energy, and the odds of IH. Results: The median sample cross-correlation between total EEG energy and ICP was 0.7, and for cerebral perfusion pressure (CPP) was 0.55. Moreover, the proposed model exhibited an accuracy of 0.70, sensitivity of 0.53, specificity of 0.79, precision of 0.54, F1-score of 0.54, and an AUC of 0.7. Comparison with existing methods: The only existing comparable methods, up to our knowledge, use 13 variables as predictor of IH, our model uses only 3, our model, as it is an extension of the generalized model is interpretable and it achieves the same performance. Conclusion: These findings hold promise for the advancement of multimodal monitoring systems in neurocritical care and the development of a non-invasive ICP monitoring tool, particularly in resource-constrained environments.

Quantitative Pupillometry for Intracranial Pressure (ICP) Monitoring in Traumatic Brain Injury: A Scoping Review.

The neurological examination has remained key for the detection of worsening in neurocritical care patients, particularly after traumatic brain injury (TBI). New-onset, unreactive anisocoria frequently occurs in such situations, triggering aggressive diagnostic and therapeutic measures to address life-threatening elevations in intracranial pressure (ICP). As such, the field needs objective, unbiased, portable, and reliable methods for quickly assessing such pupillary changes. In this area, quantitative pupillometry (QP) proves promising, leveraging the analysis of different pupillary variables to indirectly estimate ICP. Thus, this scoping review seeks to describe the existing evidence for the use of QP in estimating ICP in adult patients with TBI as compared with invasive methods, which are considered the standard practice. This review was conducted in accordance with the Joanna Briggs Institute methodology for scoping reviews, with a main search of PubMed and EMBASE. The search was limited to studies of adult patients with TBI published in any language between 2012 and 2022. Eight studies were included for analysis, with the vast majority being prospective studies conducted in high-income countries. Among QP variables, serial rather than isolated measurements of neurologic pupillary index, constriction velocity, and maximal constriction velocity demonstrated the best correlation with invasive ICP measurement values, particularly in predicting refractory intracranial hypertension. Neurologic pupillary index and ICP also showed an inverse relationship when trends were simultaneously compared. As such, QP, when used repetitively, seems to be a promising tool for noninvasive ICP monitoring in patients with TBI, especially when used in conjunction with other clinical and neuromonitoring data.

Predictive Value of Non-Invasive Intracranial Pressure Monitoring in Profoundly Impaired Traumatic Brain Injury Patients

Introduction: Trauma brain injury is an emergency condition that requires immediate precise first aid to reduce mortality rates and prevent secondary complications. Severe head injuries can lead to intracranial bleeding, thereby affecting hemodynamics. Monitoring the increase in intracranial pressure aims to mitigate the severity of head injury in patients, reducing deaths caused by brain edema. The significance of assessing the Glasgow Coma Scale (GCS) in relation to increased intracranial pressure is to determine conditions that could exacerbate physiological conditions due to head injury. The objective of this study is to determine changes in intracranial pressure among severe head injury patients. Methods: This research employs a descriptive study with a retrospective approach. Patient data were sourced from medical records of individuals treated at RS PKU Muhammadiyah Gombong, diagnosed with severe head injuries during the last year from January to December 2022. A total of 180 severe head injury patients' data were collected. Results: Research findings reveal that patients with head injuries experienced an increase in systolic blood pressure (33.3%), a decrease in pulse rate (30.5%), and a temperature within the normal range (78.9%). Conclusion: However, not all severe head injury patients exhibited elevated blood pressure, reduced pulse rate, or decreased oxygen saturation. All head injury patients experienced a decreased level of consciousness with a GCS score of less than 8.

Automation of ultrasonographic optic nerve sheath diameter measurement using convolutional neural networks.

Ultrasonographic optic nerve sheath (ONS) diameter is a noninvasive intracranial pressure (ICP) surrogate. ICP is monitored invasively in specialized intensive care units. Noninvasive ICP monitoring is important in less specialized settings. However, noninvasive ICP monitoring using ONS diameter (ONSD) is limited by the need for experts to obtain and perform measurements. We aim to automate ONSD measurements using a deep convolutional neural network (CNN) with a novel masking technique. We trained a CNN to reproduce masks that mark the ONS. The edges of the mask are defined by an expert. Eight models were trained with 1000 epochs per model. The Dice-similarity-coefficient-weighted averaged outputs of the eight models yielded the final predicted mask. Eight hundred and seventy-three images were obtained from 52 transorbital cine-ultrasonography sessions, performed on 46 patients with brain injuries. Eight hundred and fourteen images from 48 scanning sessions were used for training and validation and 59 images from four sessions for testing. Bland-Altman and Pearson linear correlation analyses were used to evaluate the agreement between CNN and expert measurements. Expert ONSD measurements and CNN-derived ONSD estimates had strong agreement (r = 0.7, p < .0001). The expert mean ONSD (standard deviation) is 5.27mm (0.43) compared to CNN mean estimate of 5.46mm (0.37). Mean difference (95% confidence interval, p value) is 0.19mm (0.10-0.27mm, p = .0011), and root mean square error is 0.27mm. A CNN can learn ONSD measurement using masking without image segmentation or landmark detection.

1314 Prediction of Raised Intracranial Pressure in Traumatic Brain Injury Patient by Non-Invasive Methods in Lower-Middle Income Countries: Systematic Review and Meta-Analysis

Abstract Background The prediction of raised Intracranial Pressure (ICP) with accuracy in Traumatic Brain Injury (TBI) patients is a clinical important decision and therapeutic tool. This study aimed to evaluate the existing methods used for non-invasive ICP monitoring in TBI patients in LMICs. Method Systematic searches of PubMed, Google Scholar, and ScienceDirect were performed from database inception to November 2021. Studies reporting the prediction of raised ICP in TBI patients by non-invasive means in LMICs were included. Pooled estimates of sensitivity, specificity, positive likelihood ratios, and negative likelihood ratios with 95%CI were calculated for each index test in JAMOVI 2.2.5. We carried out a “Medical Decision”, “Plots”, “Fagan Normogram” and the ROC curve to find the perfect discrimination point of all the five tests used for the non-invasive measurement of ICP in the TBI patients in LMICs. Results A total of 1032 studies were identified, of which, 15 included 3316 patients with male predominance (n = 2458, 74.13%). Patients' ages range from 15-96 years with 40-80 (n = 1205, 36.34%), being the most represented population. The ICP measured by Transcranial Doppler (TCD) had a sensitivity of 92.3%, and a specificity of 70%. The positive predictive value was 66.67%, with a negative predictive value of 93.33%. Furthermore, the positive Likelihood Ratio (+LR) was 3.69; 2&amp;lt;+LR&amp;lt;5, and the negative Likelihood Ratio (-LR) was 0.103; 0.1&amp;lt;-LR&amp;lt;0.2. Conclusions The TCD had shown high performance in its sensitivity and specificity, placing it on top of the other four different tests used in LMICs for the management of patients with TBI.

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.

Non-invasive monitoring of intracranial pressure changes: healthy volunteers study.

Objective: This research aims to evaluate the possible association between pulsatile near infrared spectroscopic waveform features and induced changes in intracranial pressure in healthy volunteers. Methods: An optical intracranial pressure sensor was attached to the forehead of 16 healthy volunteers. Pulsatile near infrared spectroscopic signals were acquired from the forehead during body position changes and Valsalva manoeuvers. Features were extracted from the pulsatile signals and analyses were carried out to investigate the presence of statistical differences in the features when intracranial pressure changes were induced. Classification models were developed utilizing the features extracted from the pulsatile near-infrared spectroscopic signals to classify between different body positions and Valsalva manoeuvre. Results: The presence of significant differences in the majority of the analyzed features (p 0.05) indicates the technique's ability to distinguish between variations in intracranial pressure. Furthermore, the disparities observed in the optical signal features captured by the proximal and distal photodetectors support the hypothesis that alterations in back-scattered light directly correspond to brain-related changes. Further research is required to subtract distal and proximal signals and construct predictive models employing a gold standard measurement for non-invasive, continuous monitoring of intracranial pressure. Conclusion: The study investigated the use of pulsatile near infrared spectroscopic signals to detect changes in intracranial pressure in healthy volunteers. The results revealed significant differences in the features extracted from these signals, demonstrating a correlation with ICP changes induced by positional changes and Valsalva manoeuvre. Classification models were capable of identifying changes in ICP using features from optical signals from the brain, with a sensitivity ranging from 63.07% to 80% and specificity ranging from 60.23% to 70% respectively. These findings underscored the potential of these features to effectively identify alterations in ICP. Significance: The study's results demonstrate the feasibility of using features extracted from optical signals from the brain to detect changes in ICP induced by positional changes and Valsalva manoeuvre in healthy volunteers. This represents a first step towards the non-invasive monitoring of intracranial pressure.

Assessment of increased intracranial pressure in patients with brain injury

Background: Monitoring and managing elevated intracranial pressure (ICP) is one of the core topics in neurocritical care. Although invasive methods are regarded as standard means, the recent development of non-invasive monitoring devices help clinicians handle ICP issues without additional risks of device-related complications.Current Concepts: According to the Monro–Kellie hypothesis, any brain injury that can cause a mass effect will lead to ICP elevation. Therefore, an ICP surge beyond the capacity of a compensatory reserve will decrease cerebral blood flow and may end up causing secondary brain damage. Indications for invasive ICP monitoring may vary according to the underlying conditions or the severity of brain damage. Regardless, ICP monitoring is considered when there is a risk of ICP elevation. In addition to pressure monitoring, external ventricular drainage catheters are used therapeutically to drain cerebrospinal fluid to reduce ICP. Several ICP monitoring probes are available based on pressure measurement types. Recently, non-invasive ICP monitoring methods have been developed and are increasingly used in patients with severe brain injuries. Pulsatility index from transcranial Doppler ultrasonography, quantitative pupillary light reflex from an automated pupillometer, and optic nerve sheath diameter using ultrasonography are commonly used surrogates for ICP surges in neurointensive care units.Discussion and Conclusion: ICP monitoring is essential for managing patients with severe brain injuries. Understanding the differences among the ICP monitors and determining the appropriate methods for ICP monitoring is necessary for optimizing patients’ care in the neurocritical care unit.

Noninvasive intracranial pressure monitoring throughout brain compliance guiding a ventriculoperitoneal shunt replacement in hydrocephalus-case report.

Ventriculoperitoneal (VP) shunt is the primary therapy for hydrocephalus in children; however, this technique is amenable to malfunctions, which could be detected through an assessment of clinical signs and imaging results. Furthermore, early detection can prevent patient deterioration and guide clinical and surgical treatment. A 5-year-old female with a premedical history of neonatal IVH, secondary hydrocephalus, multiple VP shunts revisions, and slit ventricle syndrome was evaluated using a noninvasive intracranial pressure monitor device at the early stages of the clinical symptoms, evidencing increased intracranial pressure and poor brain compliance. Serial MRI images demonstrated a slight ventricular enlargement, leading to the use of a gravitational VP shunt, promoting progressive improvement. On the follow-up visits, we used the noninvasive ICP monitoring device to guide the shunt adjustments until symptom resolution. Furthermore, the patient has been asymptomatic for the past 3years without requiring new shunt revisions. Slit ventricle syndrome and VP shunt dysfunctions are challenging diagnoses for the neurosurgeon. The noninvasive intracranial monitoring has allowed a closer follow-up assisting early assessment of brain compliance changes related to a patient's symptomatology. Furthermore, this technique has high sensitivity and specificity in detecting alterations in the intracranial pressure, serving as a guide for the adjustments of programmable VP shunts, which may improve the patient's quality of life. Noninvasive ICP monitoring may lead to a less invasive assessment of patients with slit ventricle syndrome and could be used as a guide for adjustments of programmable shunts.

Effect of intracranial pressure on photoplethysmographic waveform in different cerebral perfusion territories: A computational study.

Background: Intracranial photoplethysmography (PPG) signals can be measured from extracranial sites using wearable sensors and may enable long-term non-invasive monitoring of intracranial pressure (ICP). However, it is still unknown if ICP changes can lead to waveform changes in intracranial PPG signals. Aim: To investigate the effect of ICP changes on the waveform of intracranial PPG signals of different cerebral perfusion territories. Methods: Based on lump-parameter Windkessel models, we developed a computational model consisting three interactive parts: cardiocerebral artery network, ICP model, and PPG model. We simulated ICP and PPG signals of three perfusion territories [anterior, middle, and posterior cerebral arteries (ACA, MCA, and PCA), all left side] in three ages (20, 40, and 60years) and four intracranial capacitance conditions (normal, 20% decrease, 50% decrease, and 75% decrease). We calculated following PPG waveform features: maximum, minimum, mean, amplitude, min-to-max time, pulsatility index (PI), resistive index (RI), and max-to-mean ratio (MMR). Results: The simulated mean ICPs in normal condition were in the normal range (8.87-11.35mmHg), with larger PPG fluctuations in older subject and ACA/PCA territories. When intracranial capacitance decreased, the mean ICP increased above normal threshold (>20mmHg), with significant decreases in maximum, minimum, and mean; a minor decrease in amplitude; and no consistent change in min-to-max time, PI, RI, or MMR (maximal relative difference less than 2%) for PPG signals of all perfusion territories. There were significant effects of age and territory on all waveform features except age on mean. Conclusion: ICP values could significantly change the value-relevant (maximum, minimum, and amplitude) waveform features of PPG signals measured from different cerebral perfusion territories, with negligible effect on shape-relevant features (min-to-max time, PI, RI, and MMR). Age and measurement site could also significantly influence intracranial PPG waveform.

Non-Invasive Intracranial Pressure Monitoring.

(1) Background: Intracranial pressure (ICP) monitoring plays a key role in the treatment of patients in intensive care units, as well as during long-term surgeries and interventions. The gold standard is invasive measurement and monitoring via ventricular drainage or a parenchymal probe. In recent decades, numerous methods for non-invasive measurement have been evaluated but none have become established in routine clinical practice. The aim of this study was to reflect on the current state of research and shed light on relevant techniques for future clinical application. (2) Methods: We performed a PubMed search for "non-invasive AND ICP AND (measurement OR monitoring)" and identified 306 results. On the basis of these search results, we conducted an in-depth source analysis to identify additional methods. Studies were analyzed for design, patient type (e.g., infants, adults, and shunt patients), statistical evaluation (correlation, accuracy, and reliability), number of included measurements, and statistical assessment of accuracy and reliability. (3) Results: MRI-ICP and two-depth Doppler showed the most potential (and were the most complex methods). Tympanic membrane temperature, diffuse correlation spectroscopy, natural resonance frequency, and retinal vein approaches were also promising. (4) Conclusions: To date, no convincing evidence supports the use of a particular method for non-invasive intracranial pressure measurement. However, many new approaches are under development.

In Vitro Evaluation of a Non-Invasive Photoplethysmography Based Intracranial Pressure Sensor

Intracranial pressure (ICP) is an important measurement in the treatment of Traumatic Brain Injury (TBI). Currently, ICP can only be measured invasively, which exposes patients to operative risk and can only be performed by neurosurgeons. Hence, there is a significant need for a non-invasive ICP technology. This paper describes the evaluation of a novel non-invasive intracranial pressure (nICP) monitor which uses the Photoplethysmogram (PPG) to measure the ICP. The monitor was evaluated in an in vitro model that simulated cerebral haemodynamics and allowed the controlled manipulation of ICP. A number of features from the PPG were extracted and utilised in a machine learning model to estimate ICP. Three separate measurements in which the ICP was varied were performed, and the estimated ICP (nICP) was compared with reference (invasive) ICP measurements. The ICP estimated by the nICP monitor was highly correlated with reference ICP measurements (Pearson’s correlation coefficient between 0.95 and 0.98). The nICP monitor also showed a low Root Mean Square Error from the reference ICP measure (3.12, 1.48, and 1.45 mmHg). Analysis of agreement by Bland and Altman also revealed good agreement between the two techniques. The optical nICP monitor was able to estimate the ICP non-invasively from an in vitro model simulating intracranial hypertension. The non-invasive ICP monitor showed very promising results which can set the base for further investigations. This work contributes significantly to the quest for non-invasive ICP monitoring in Traumatic Brain Injury (TBI), and paves the way for further research in this field.

Using near-infrared spectroscopy and a random forest regressor to estimate intracranial pressure.

.SignificanceIntracranial pressure (ICP) measurements are important for patient treatment but are invasive and prone to complications. Noninvasive ICP monitoring methods exist, but they suffer from poor accuracy, lack of generalizability, or high cost.AimWe previously showed that cerebral blood flow (CBF) cardiac waveforms measured with diffuse correlation spectroscopy can be used for noninvasive ICP monitoring. Here we extend the approach to cardiac waveforms measured with near-infrared spectroscopy (NIRS).ApproachChanges in hemoglobin concentrations were measured in eight nonhuman primates, in addition to invasive ICP, arterial blood pressure, and CBF changes. Features of average cardiac waveforms in hemoglobin and CBF signals were used to train a random forest (RF) regressor.ResultsThe RF regressor achieves a cross-validated ICP estimation of , mean squared error (MSE), and 95% confidence interval (CI) of on oxyhemoglobin concentration changes; , MSE, and 95% CI of on total hemoglobin concentration changes; and , MSE, and 95% CI of on CBF changes.ConclusionsThis study provides a proof of concept for the use of NIRS in noninvasive ICP estimation.

The application value of CT radiomics features in predicting pressure amplitude correlation index in patients with severe traumatic brain injury.

PurposeTo explore the application value of a machine learning model based on CT radiomics features in predicting the pressure amplitude correlation index (RAP) in patients with severe traumatic brain injury (sTBI).MethodsRetrospectively analyzed the clinical and imaging data in 36 patients with sTBI. All patients underwent surgical treatment, continuous ICP monitoring, and invasive arterial pressure monitoring. The pressure amplitude correlation index (RAP) was collected within 1 h after surgery. Three volume of interest (VOI) was selected from the craniocerebral CT images of patients 1 h after surgery, and a total of 93 radiomics features were extracted from each VOI. Three models were established to be used to evaluate the patients' RAP levels. The accuracy, precision, recall rate, F1 score, receiver operating characteristic (ROC) curve, and area under the curve (AUC) were used to evaluate the predictive performance of each model.ResultsThe optimal number of features for three predicting models of RAP was five, respectively. The accuracy of predicting the model of the hippocampus was 77.78%, precision was 88.24%, recall rate was 60%, the F1 score was 0.6, and AUC was 0.88. The accuracy of predicting the model of the brainstem was 63.64%, precision was 58.33%, the recall rate was 60%, the F1 score was 0.54, and AUC was 0.82. The accuracy of predicting the model of the thalamus was 81.82%, precision was 88.89%, recall rate was 75%, the F1 score was 0.77, and AUC was 0.96.ConclusionsCT radiomics can predict RAP levels in patients with sTBI, which has the potential to establish a method of non-invasive intracranial pressure (NI-ICP) monitoring.

Noninvasive intracranial pressure in patients with traumatic brain injury

Monitoring and treatment of intracranial pressure are extremely important procedures in the management of patients with traumatic brain injury. The monitoring methods currently marketed are invasive and are not suitable for all patients. In addition to the risks offered, they are not available on all services. This study aims to describe the cases of five patients with traumatic brain injury of different severity who underwent noninvasive monitoring of intracranial pressure in the acute phase of the injury, relating the changes identified with the clinical picture presented. Patients showed important changes in intracranial pressure wave morphology, possibly related to the lesions, clinical presentation and therapeutic interventions used.

Non-Invasive Intracranial Pressure Monitoring and Its Applicability in Spaceflight.

INTRODUCTION: Neuro-ophthalmic findings collectively defined as Spaceflight-Associated Neuro-ocular Syndrome (SANS) are one of the leading health priorities in astronauts engaging in long duration spaceflight or prolonged microgravity exposure. Though multifactorial in etiology, similarities to terrestrial idiopathic intracranial hypertension (IIH) suggest these changes may result from an increase or impairing in intracranial pressure (ICP). Finding a portable, accessible, and reliable method of monitoring ICP is, therefore, crucial in long duration spaceflight. A review of recent literature was conducted on the biomedical literature search engine PubMed using the search term "non-invasive intracranial pressure". Studies investigating accuracy of noninvasive and portable methods were assessed. The search retrieved different methods that were subsequently grouped by approach and technique. The majority of publications included the use of ultrasound-based methods with variable accuracies. One of which, noninvasive ICP estimation by optical nerve sheath diameter measurement (nICP_ONSD), presented the highest statistical correlation and prediction values to invasive ICP, with area under the curve (AUC) ranging from 0.75 to 0.964. One study even considers a combination of ONSD with transcranial Doppler (TCD) for an even higher performance. Other methods, such as near-infrared spectroscopy (NIRS), show positive and promising results [good statistical correlation with invasive techniques when measuring cerebral perfusion pressure (CPP): r = 0.83]. However, for its accessibility, portability, and accuracy, ONSD seems to present itself as the up to date, most reliable, noninvasive ICP surrogate and a valuable spaceflight asset.Félix H, Santos Oliveira E. Non-invasive intracranial pressure monitoring and its applicability in spaceflight. Aerosp Med Hum Perform. 2022; 93(6):517-531.

Noninvasive monitoring of intracranial pressure after cardiac surgery: case report

Background: Heart valves are important structures that play an essential role in directing blood flow; changes in the functioning of these structures may require cardiac surgery with cardiopulmonary bypass. The behavior of intracranial pressure (ICP) in patients undergoing this type of surgery is unknown. Objective: aim of this study was to report alterations in the waveform morphology of ICP in a patient submitted to cardiac surgery with cardiopulmonary bypass. Case Description: This report provides data on ICP waveform morphology (P1 and P2 peaks) monitored before, immediately after, and on the 5th day after cardiac surgery. In the preoperative evaluation, the morphology of the patient's ICP waveforms was slightly altered, possibly due to the underlying cardiovascular disease. In the second measurement of the ICP waveforms, performed after surgery, the wave morphology of the ICP was normal. On the 5th PO day, after the patient presented clinical signs of neurological complications, the third ICP measurement was performed, which showed that the morphology of the ICP wave was altered.Conclusions: The use of non-invasive monitoring of ICP is of great importance in patients undergoing cardiac surgery, with the aim of diagnosing, preventing and/or enabling rapid treatment in cases where there is an evolution of more severe neurological complications that may lead to death.

Invention of a non-invasive intracranial pressure (ICP) monitoring system – an enlightenment from a hydrocephalus study

Background Mechanical obstruction is the most common cause of shunt failure for hydrocephalic patients. However, the diagnosis is extremely challenging and often requires invasive testing methods. Thus, a simple and non-invasive technique is in urgent need to predict the intracranial pressure (ICP) of hydrocephalic patients during their post-surgical follow-up, which could help neurosurgeons to determine the conditions of the shunt system. Materials and methods Two groups of patients were enrolled in the current study. In group I, patients were enrolled as they were diagnosed with high ICP hydrocephalus and received shunt surgery. The shunt valve pressures were taken for their post-surgical ICP. Meanwhile, the participants of group II exhibited abnormally increased lumbar puncture opening pressure (LPOP; from 180 to 400 mmH2O). Both the ICP and LPOP were used to match with their corresponding tympanic membrane temperature (TMT). Results When patients’ ICP were in the normal range (group I, from 50 to 180 mmH2O), the TMT correlated with ICP in a linear regression model (R 2 = 0.59, p < 0.001). Interestingly, when patients exhibited above-normal ICP (LPOP was from 180 to 400 mmH2O), their TMT fit well with the ICP in a third-order polynomial regression (R 2 = 0.88). When the ICP was 287.98 mmH2O, the TMT approached the vertex, which was 38.54 °C. Based on this TMT-ICP algorithm, we invented a non-invasive ICP monitor system. Interestingly, a tight linear correlation was detected between the ICP data drawn from the non-invasive device and Codman ICP monitoring system (R 2 = 0.93, p < 0.01). Conclusions We believe the TMT-ICP algorithm (the Y-Jiang model) could be used for preliminary prediction of shunt malfunction as well as monitoring ICP changes.

Preliminary evaluation of a non-invasive device for monitoring intracranial pressure waveforms in dogs.

The objective of this study was to compare waveforms obtained with a new device for the non-invasive monitoring of intracranial pressure (ICP) in dogs with and without neurological disease. This prospective study was conducted on both neurologically normal dogs and dogs with neurological diseases. First, non-invasive ICP waveforms were recorded in normal dogs using the Braincare® BcMM 2000 monitor while the dogs were under general anaesthesia induced for procedures unrelated to this study. The dogs were positioned in lateral recumbency, and the sensor was placed over the skin of the parietal region. Secondly, non-invasive ICP waveforms were monitored in dogs with brain and spinal disease until waveforms with characteristic peaks were acquired. All the recorded signals were amplified, filtered and digitalized, by the device, and then transferred to a computer for analysis. Normal pulse waveforms indicating normal brain complacency were observed in eight neurologically normal dogs. In six dogs with brain disease, abnormal pulse waveforms were observed suggesting increased ICP and decreased brain complacency. Four dogs with spinal disease undergoing myelography, had normal waveforms before contrast medium injection and abnormal pulse waveforms during contrast medium injection, indicating a potential increase in ICP. Based on these preliminary observations, this method was capable of detecting abnormal pulse waveforms that suggested increased ICP.

Introduction of a Novel, Continuous, Noninvasive Estimation of Intracranial Pressure and Cerebral Perfusion Pressure Based on Tympanic Membrane Temperature

Hydrocephalus is a common but potentially life-threatening condition. However, valve malfunction makes further diagnosis difficult. Thus, we tried to develop a noninvasive method to detect the hydrocephalus intracranial pressure (ICP) during routine follow-up. In group I, the patient was recruited because a spinal tap test was necessary for either disease diagnosis or treatment. In group II, patients were diagnosed with high ICP hydrocephalus and received shunt surgery. The tympanic membrane temperatures (TMTs) were recorded and plotted against the spinal tap pressure (STP) and shunt valve pressures. All patients in group I showed an above-normal STP (from 180 to 400 mm H2O). The STP presents with an inverted U-shaped curve when it is plotted against TMT (R2= 0.9). When the STP was 286.1 mm H2O, the TMT approached its peak value, which was 38.61°C (101.5°F). However, when ICP was in the normal range (50-200 mm H2O), the TMT correlated with ICP in a linear regression model (R2= 0.69; P < 0.001). In addition, the cerebral perfusion pressure (CPP) was calculated and plotted against TMT. The TMT-CPP was also shown as a parabola (R2= 0.74). Based on the TMT-ICP algorithm, we invented a noninvasive ICP monitor system, which performs in a manner comparable to the Codman ICP Transducer (R2= 0.9; P < 0.01). Both Y-Jiang TMT-ICP and TMT-CPP algorithms are useful to monitor the shunt outcomes and identify potential shunt failure. More importantly, these algorithms open the possibility for the rational acquisition of ICP and CPP noninvasively.