Optimization of number and range of shunt valve performance levels in infant hydrocephalus: a machine learning analysis.

Shunt surgery is the main treatment modality for hydrocephalus, the leading cause of brain surgery in children. The efficacy of shunt surgery, particularly in infant hydrocephalus, continues to present serious challenges in achieving improved outcomes. The crucial role of correct adjustments of valve performance levels in shunt outcomes has been underscored. However, there are discrepancies in the performance levels of valves from different companies. This study aims to address this concern by optimizing both the number and range of valve performance levels for infant hydrocephalus, aiming for improved shunt surgery outcomes. We conducted a single-center cohort study encompassing infant hydrocephalus cases that underwent initial shunt surgery without subsequent failure or unimproved outcomes. An unsupervised hierarchical machine learning method was utilized for clustering and reporting the valve drainage pressure values for all patients within each identified cluster. The optimal number of clusters corresponds to the number of valve performance levels, with the valve drainage pressure ranges within each cluster indicating the pressure range for each performance level. Comparisons based on the Silhouette coefficient between 3-7 clusters revealed that this coefficient for the 4-cluster (4-performance level) was at least 28.3% higher than that of other cluster formations in terms of intra-cluster similarity. The Davies-Bouldin index for the 4-performance level was at least 37.2% lower than that of other configurations in terms of inter-cluster dissimilarity. Cluster stability, indicated by a Jaccard index of 71% for the 4-performance level valve, validated the robustness, reliability, and repeatability of our findings. Our suggested optimized drainage pressure ranges for each performance level (1.5-5.0, 5.0-9.0, 9.0-15.0, and 15.0-18.0 cm H2O) may potentially assist neurosurgeons in improving clinical outcomes for patients with shunted infantile hydrocephalus.

Feasibility of assessing non-invasive intracranial compliance using FSI simulation-based and MR elastography-based brain stiffness.

Intracranial compliance (ICC) refers to the change in intracranial volume per unit change in intracranial pressure (ICP). Magnetic resonance elastography (MRE) quantifies brain stiffness by measuring the shear modulus. Our objective is to investigate the relationship between ICC and brain stiffness through fluid-structure interaction (FSI) simulation, and to explore the feasibility of using MRE to assess ICC based on brain stiffness. This is invaluable due to the clinical importance of ICC, as well as the fast and non-invasive nature of the MRE procedure. We employed FSI simulation in hydrocephalus patients with aqueductal stenosis to non-invasively calculate ICP which is the basis of the calculation of ICC and FSI-based brain stiffness. The FSI simulated parameters used have been validated with experimental data. Our results showed that there is no relationship between FSI simulated-based brain stiffness and ICC in hydrocephalus patients. However, MRE-based brain stiffness may be sensitive to changes in intracranial fluid dynamic parameters such as cerebral perfusion pressure (CPP), cerebral blood flow (CBF), and ICP, as well as to mechano-vascular changes in the brain, which are determining parameters in ICC assessment. Although optimism has been found regarding the assessment of ICC using MRE-based brain stiffness, especially for acute-onset brain disorders, further studies are necessary to clarify their direct relationship.

Why Intracranial Compliance Is Not Utilized as a Common Practical Tool in Clinical Practice.

Intracranial compliance (ICC) holds significant potential in neuromonitoring, serving as a diagnostic tool and contributing to the evaluation of treatment outcomes. Despite its comprehensive concept, which allows consideration of changes in both volume and intracranial pressure (ICP), ICC monitoring has not yet established itself as a standard component of medical care, unlike ICP monitoring. This review highlighted that the first challenge is the assessment of ICC values, because of the invasive nature of direct measurement, the time-consuming aspect of non-invasive calculation through computer simulations, and the inability to quantify ICC values in estimation methods. Addressing these challenges is crucial, and the development of a rapid, non-invasive computer simulation method could alleviate obstacles in quantifying ICC. Additionally, this review indicated the second challenge in the clinical application of ICC, which involves the dynamic and time-dependent nature of ICC. This was considered by introducing the concept of time elapsed (TE) in measuring the changes in volume or ICP in the ICC equation (volume change/ICP change). The choice of TE, whether short or long, directly influences the ICC values that must be considered in the clinical application of the ICC. Compensatory responses of the brain exhibit non-monotonic and variable changes in long TE assessments for certain disorders, contrasting with the mono-exponential pattern observed in short TE assessments. Furthermore, the recovery behavior of the brain undergoes changes during the treatment process of various brain disorders when exposed to short and long TE conditions. The review also highlighted differences in ICC values across brain disorders with various strain rates and loading durations on the brain, further emphasizing the dynamic nature of ICC for clinical application. The insight provided in this review may prove valuable to professionals in neurocritical care, neurology, and neurosurgery for standardizing ICC monitoring in practical application related to the diagnosis and evaluation of treatment outcomes in brain disorders.

Enhanced Ionic Polymer-Metal Composites with Nanocomposite Electrodes for Restoring Eyelid Movement of Patients with Ptosis.

The present study aims to use enhanced ionic polymer-metal composites (IPMC) as an artificial muscle (a soft-active actuator) to restore eyelid movement of patients with ptosis. The previous eyelid movement mechanisms contained drawbacks, specifically in the lower eyelid. We used finite element analysis (FEA) to find the optimal mechanism among two different models (A and B). In addition to common electrodes of IPMC (gold and platinum), the bovine serum albumin (BSA) and microcrystalline cellulose (MCC) polymers, with optimal weight percentages of carbon nanotube (CNT) nanofiller, were also utilized as non-metallic electrodes to improve the efficiency of the IPMC actuator. In both models, IPMC with nanocomposite electrodes had higher efficiency as compared to the metallic electrodes. In model A, which moved eyelids indirectly, IPMC with MCC-CNT electrode generated a higher force (25.4%) and less stress (5.9 times) as compared to IPMC with BSA-CNT electrode. However, the use of model A (even with IPMCs) with nanocomposite electrodes can have limitations such as possible malposition issues in the eyelids (especially lower). IPMC with MCC-CNT nanocomposite electrode under model B, which moved eyelids directly, was the most efficient option to restore eyelid movement. It led to higher displacements and lower mechanical stress damage as compared to the BSA-CNT. This finding may provide surgeons with valuable data to open a window in the treatment of patients with ptosis.

A mathematical framework for the dynamic interaction of pulsatile blood, brain, and cerebrospinal fluid.

BACKGROUND: Shedding light on less-known aspects of intracranial fluid dynamics may be helpful to understand the hydrocephalus mechanism. The present study suggests a mathematical framework based on in vivo inputs to compare the dynamic interaction of pulsatile blood, brain, and cerebrospinal fluid (CSF) between the healthy subject and the hydrocephalus patient. METHOD: The input data for the mathematical formulations was pulsatile blood velocity, which was measured using cine PC-MRI. Tube law was used to transfer the created deformation by blood pulsation in the vessel circumference to the brain domain. The pulsatile deformation of brain tissue with respect to time was calculated and considered to be inlet velocity in the CSF domain. The governing equations in all three domains were continuity, Navier-Stokes, and concentration. We used Darcy law with defined permeability and diffusivity values to define the material properties in the brain. RESULTS: We validated the preciseness of the CSF velocity and pressure through the mathematical formulations with cine PC-MRI velocity, experimental ICP, and FSI simulated velocity and pressure. We used the analysis of dimensionless numbers including Reynolds, Womersley, Hartmann, and Peclet to evaluate the characteristics of the intracranial fluid flow. In the mid-systole phase of a cardiac cycle, CSF velocity had the maximum value and CSF pressure had the minimum value. The maximum and amplitude of CSF pressure, as well as CSF stroke volume, were calculated and compared between the healthy subject and the hydrocephalus patient. CONCLUSION: The present in vivo-based mathematical framework has the potential to gain insight into the less-known points in the physiological function of intracranial fluid dynamics and the hydrocephalus mechanism.

Long-term recovery behavior of brain tissue in hydrocephalus patients after shunting.

The unpredictable complexities in hydrocephalus shunt outcomes may be related to the recovery behavior of brain tissue after shunting. The simulated cerebrospinal fluid (CSF) velocity and intracranial pressure (ICP) over 15 months after shunting were validated by experimental data. The mean strain and creep of the brain had notable changes after shunting and their trends were monotonic. The highest stiffness of the hydrocephalic brain was in the first consolidation phase (between pre-shunting to 1 month after shunting). The viscous component overcame and damped the input load in the third consolidation phase (after the fifteenth month) and changes in brain volume were stopped. The long-intracranial elastance (long-IE) changed oscillatory after shunting and there was not a linear relationship between long-IE and ICP. We showed the long-term effect of the viscous component on brain recovery behavior of hydrocephalic brain. The results shed light on the brain recovery mechanism after shunting and the mechanisms for shunt failure.

A New Definition for Intracranial Compliance to Evaluate Adult Hydrocephalus After Shunting.

The clinical application of intracranial compliance (ICC), ∆V/∆P, as one of the most critical indexes for hydrocephalus evaluation was demonstrated previously. We suggest a new definition for the concept of ICC (long-term ICC) where there is a longer amount of elapsed time (up to 18 months after shunting) between the measurement of two values (V1 and V2 or P1 and P2). The head images of 15 adult patients with communicating hydrocephalus were provided with nine sets of imaging in nine stages: prior to shunting, and 1, 2, 3, 6, 9, 12, 15, and 18 months after shunting. In addition to measuring CSF volume (CSFV) in each stage, intracranial pressure (ICP) was also calculated using fluid-structure interaction simulation for the noninvasive calculation of ICC. Despite small increases in the brain volume (16.9%), there were considerable decreases in the ICP (70.4%) and CSFV (80.0%) of hydrocephalus patients after 18 months of shunting. The changes in CSFV, brain volume, and ICP values reached a stable condition 12, 15, and 6 months after shunting, respectively. The results showed that the brain tissue needs approximately two months to adapt itself to the fast and significant ICP reduction due to shunting. This may be related to the effect of the "viscous" component of brain tissue. The ICC trend between pre-shunting and the first month of shunting was descending for all patients with a "mean value" of 14.75 ± 0.6 ml/cm H2O. ICC changes in the other stages were oscillatory (nonuniform). Our noninvasive long-term ICC calculations showed a nonmonotonic trend in the CSFV-ICP graph, the lack of a linear relationship between ICC and ICP, and an oscillatory increase in ICC values during shunt treatment. The oscillatory changes in long-term ICC may reflect the clinical variations in hydrocephalus patients after shunting.

Cerebrospinal fluid hydrocephalus shunting: cisterna magna, ventricular frontal, ventricular occipital.

Despite advances in cerebrospinal fluid shunting technology, complications remain a significant concern. There are some contradictions about the effectiveness of proximal catheter entry sites that decrease shunt failures. We aim to compare efficiency of shunts with ventricular frontal, ventricular occipital, and cisterna magna entry sites. The systemic search was conducted in the database from conception to February 16, 2022 following guidelines of PRISMA. Between 2860 identified articles, 24 articles including 6094 patients were used for data synthesis. The aggregated results of all patients showed that "overall shunt failure rate per year" in mixed hydrocephalus with ventricular frontal and occipital shunts, and cisterna magna shunt (CMS) were 9.0%, 12.6%, and 30.7%, respectively. The corresponding values for "shunt failure rate" due to obstruction were 15.3%, 31.5%, and 10.2%, respectively. The similar results for "shunt failure rate" due to infection were 11.3%, 9.1%, and 27.2%, respectively. The related values for "shunt failure rate" due to overdrainage were 2.9%, 3.9%, and 13.6%, respectively. CMS was successful in the immediate resolution of clinical symptoms. Shunting through an occipital entry site had a greater likelihood of inaccurate catheter placement and location. Contrary to possible shunt failure due to overdrainage, the failure likelihood due to obstruction and infection in pediatric patients was higher than that of mixed hydrocephalus patients. In both mixed and pediatric hydrocephalus, obstruction and overdrainage were the most and least common complications of ventricular frontal and occipital shunts, respectively. The most and least common complications of mixed CMS were infection and obstruction, respectively.

The role of operating variables in improving the performance of skull base grinding.

Control of the thermal and physical damage during skull base grinding is of great importance. We assess the effects of bur material (3 materials), angle of the bur (10 angles), bur diameter (10 diameters), gas coolant (4 coolants), and grinding time (10 times) to evaluate the role of operating variables in thermal and physical damage during skull bone grinding. After validation of finite element analysis (FEA) results with experimental data, the temperature in the grinding site and axial force are calculated using FEA. The use of a diamond bur leads to at least 24.48 and 12.9% reduction in thermal and physical damage, respectively. A change in angle of the bur from 0º to 90º leads to a 19.76-31.62 times increment in axial force. An increase in bur diameter from 1 to 5.5 mm led to 10.78-14.36% and 23.43-43.90% increase in maximum temperature and axial force, respectively. However, a bur diameter between 2.5 and 4 mm could provide enough grinding force with less thermal damage. Skull base grinding with dry (D) and normal saline (NS) coolants was always accompanied with thermal damage. The results of maximum and duration of temperature, axial force, and surface defect evaluation show CO2 coolants (especially internal CO2 coolant) are the best options to decrease thermal damage. The equations of temperature and axial force were estimated by regression analysis. This may be used as a guideline for neurosurgeons to control damage during skull base grinding and can also be helpful for the programming of robot-assisted skull grinding during surgery.

Thermal and physical damage in skull base drilling using gas cooling modes: FEM simulation and experimental evaluation.

BACKGROUND: Skull base drilling, as a high-risk process, is one of the most important techniques of skull base surgeries. METHODS: The temperature, thrust force, and torque were calculated using finite element method (FEM) simulation under two conventional cooling models, and internal and external CO2 cooling modes at four rotational speeds (1000-4000 rpm). The temperatures at the bottom and on the surface of the drilling site were measured experimentally using a thermometer and a thermographic camera, respectively. The results were then compared with FEM results. RESULTS: The efficiency rates of CO2 coolants in reducing the maximum temperature, thrust force, and torque were at least 5.0-11.2%, 16.5-33.8%, and 6.9-11.3% higher than conventional cooling modes, respectively. The experimental results indicated that, in contrast to the maximum temperature, temperature durability was 72.7-107.3% higher in the conventional cooling modes than the cooling modes with external CO2 coolant systems. The cracks and surface defects were less in the CO2 coolants than the other cooling modes. The maximum temperature after the second and third drillings increased by 17.7 and 26.8%, compared to the first drilling in the conventional cooling modes. On the other hand, the repeated drillings had no impact on the temperature in the CO2 cooling modes. CONCLUSION: Skull base drilling with a rotational speed of 2000 rpm in the cooling mode of an external CO2 coolant, even for repeated drillings, can lead to a skull drilling process with minimum risk of drill bit breakage and thermal and physical damage.

Boundary conditions investigation to improve computer simulation of cerebrospinal fluid dynamics in hydrocephalus patients.

Three-D head geometrical models of eight healthy subjects and 11 hydrocephalus patients were built using their CINE phase-contrast MRI data and used for computer simulations under three different inlet/outlet boundary conditions (BCs). The maximum cerebrospinal fluid (CSF) pressure and the ventricular system volume were more effective and accurate than the other parameters in evaluating the patients' conditions. In constant CSF pressure, the computational patient models were 18.5% more sensitive to CSF volume changes in the ventricular system under BC "C". Pulsatile CSF flow rate diagrams were used for inlet and outlet BCs of BC "C". BC "C" was suggested to evaluate the intracranial compliance of the hydrocephalus patients. The results suggested using the computational fluid dynamic (CFD) method and the fully coupled fluid-structure interaction (FSI) method for the CSF dynamic analysis in patients with external and internal hydrocephalus, respectively.

Hydrodynamic comparison of shunt and endoscopic third ventriculostomy in adult hydrocephalus using in vitro models and fluid-structure interaction simulation.

OBJECTIVE: The comparison of the efficiency of shunt placement and endoscopic third ventriculostomy (ETV) in treating of adult hydrocephalus patients with various intensities and different obstruction intensities in the aqueduct of Sylvius (AS). METHODS: In vitro models with separated ventricles were simulated and implemented for modeling shunt and ETV surgeries in one healthy subject and hydrocephalus patients with various intensities, as well as three different obstruction intensities in AS and under two cerebrospinal fluid (CSF) dynamic conditions. The fluid-structure interaction simulation was also carried out to validate in vitro results. RESULTS: The efficiency of both methods in reducing the maximum CSF pressure in the subarachnoid space (MCPS) decreased by an increase in the patient's intensities. Contrary to shunting, the efficiency of ETV in reducing MCPS demonstrated a decline (8.3-16.4%) by an increase in obstruction levels in AS. Based on the findings, shunt efficiency in decreasing MCPS in patients with low intensity was more remarkable compared to ETV. However, ETV was more efficient than shunt in the patient with intracranial hypertension. Further, shunt placement and ETV led to a significant reduction in the amplitude of CSF pressure in the SAS (ACPS) in patients with sneezing, coughing, Valsalva maneuver, and exercising effects in contrast to other patients. Moreover, ACPS reduction was not related to the intensity of the disease in both treatment methods. In contrast to shunt, an increase in the obstruction level in AS led to a reduction in ACPS in ETV in both CSF dynamic conditions. CONCLUSIONS: The noises from irregular disorders increased the discharging of CSF after shunt placement, and activities such as sneezing, coughing, Valsalva maneuvers, and exercising increased the risk of shunt overdrainage by 10.4~47.8%, especially in the patient with intracranial hypertension. Based on the proposed in vitro ETV and shunt models, an increase of head compliance was higher in ETV compared to the shunt. Eventually, an increase in the obstruction level of AS after ETV led to a decline in head compliance in contrast to shunt.

Effect of bifurcation in the hemodynamic changes and rupture risk of small intracranial aneurysm.

The role of bifurcations is prominent in the intracranial aneurysm (IA) evaluation, and there are many contradictions and complexities in the rupture risk of small IA. Therefore, in the present study, the effect of bifurcation on the manner of hemodynamic changes and the rupture risk of the small middle cerebral artery (MCA) aneurysm is investigated. 3D anatomical models of the MCAs of 21 healthy subjects, 19 patients/IA/bifurcation, and 19 patients/IA were generated, and the models were analyzed by the computational fluid dynamic (CFD) analysis. The presence of bifurcation in the pathway of the blood flow in the parent artery of healthy subjects has reduced the maximum velocity, flow rate, and wall shear stress (WSS) by 25.8%, 38.6%, and 11.1%, respectively. The bifurcation decreased the maximum velocity and flow rate in the neck and sac of the aneurysm by 1.65~2.1 times, respectively. It increased the maximum WSS, and phase lag between the WSS graph of healthy subjects and patients by 12.8%~13.9% and 10.2%~40.4%, respectively. The effect of bifurcation on the Womersley number change in the aneurysm was insignificant, and the blood flow was in the laminar flow condition in all samples. The results also showed bifurcation increased the phase lag between the flow rate and pressure gradient graphs up to approximately 1.5 times. The rupture prediction index for patients/IA/bifurcation and patients/IA was 62.1%(CV = 4.1) and 51.8%(CV = 4.4), respectively. Thus, in equal conditions, the presence of bifurcation increased the probability of the rupture of the aneurysm by 19.9%.

Correlation of a new hydrodynamic index with other effective indexes in Chiari I malformation patients with different associations.

This study aimed to find a new CSF hydrodynamic index to assess Chiari type I malformation (CM-I) patients' conditions and examine the relationship of this new index with morphometric and volumetric changes in these patients and their clinical symptoms. To this end, 58 CM-I patients in four groups and 20 healthy subjects underwent PC-MRI. Ten morphometric and three volumetric parameters were calculated. The CSF hydrodynamic parameters were also analyzed through computational fluid dynamic (CFD) simulation. The maximum CSF pressure was identified as a new hydrodynamic parameter to assess the CM-I patients' conditions. This parameter was similar in patients with the same symptoms regardless of the group to which they belonged. The result showed a weak correlation between the maximum CSF pressure and the morphometric parameters in the patients. Among the volumetric parameters, PCF volume had the highest correlation with the maximum CSF pressure, which its value being higher in patients with CM-I/SM/scoliosis (R2 = 65.6%, P = 0.0022) than in the other patients. PCF volume was the more relevant volumetric parameter to assess the patients' symptoms. The values of PCF volume were greater in patients that headache symptom was more obvious than other symptoms, as compared to the other patients.

The effect of electromagnetic field on decreasing and increasing of the growth and proliferation rate of dermal fibroblast cell.

Maintaining the health of dermal fibroblast cells and controlling their growth and proliferation would directly affect the health of skin tissues. The present study encompassed three control and three experimental specimens, which were different in terms of the duration of exposure to electromagnetic field (EMF) and intensity. With a decrease in intensity from 2 to 1 mT during 24, 48, and 72 h after exposing the cells to EMF, the frequency of the sample fibroblast cells increased by 60.3%, 144.9%, and 90.1%, respectively. With an increase in intensity from 3 to 4 mT during 48 and 72 h of exposure to EMF, the frequencies of the sample fibroblast cells decreased by 6.8% and 86.7%, respectively. It seems to be possible to achieve the most desirable condition to help the restoration of wounds and skin lesions through decreasing the exposure intensity from 2 to 0.5 mT and increasing EMF exposure time from 24 to 72 h simultaneously and non-invasively. The most desirable approach to improve the treatment of skin cancers non-invasively is to increase the intensity from 3 to 5 mT and to enhance EMF exposure time from 48 to 72 h.

Effect of Ambient Temperature Changes on Blood Flow in Anterior Cerebral Artery of Patients with Skull Prosthesis.

BACKGROUND: In many cases, an injury to the head leads to the replacement of a part of the skull with materials such as titanium and polyether ether ketone. METHODS: Three-dimensional heads model of 15 healthy individuals and 13 patients were prepared. The models were simulated using thermal fluid structure interaction analysis to evaluate the effects of cold (5°C) and hot (55°C) temperatures of the skull on the conditions of blood flow in the anterior cerebral artery. RESULTS: The results showed negligible changes (<3%) in wall shear stress (WSS) vessel and von Mises stress between the healthy individuals and patients both at 25°C and 55°C. However, at 5°C, the values of these 2 parameters in the patients were 2.1 and 2.5 times those in healthy individuals, respectively. The value of WSS in healthy individuals and the patients in cold temperature was 1.2 and 2.9 times those at normal temperature. The corresponding values for von Mises stress were 1.1 and 2.2, respectively. Accordingly, the stress changes between cold and hot ambient temperatures were found to be negligible in all samples. CONCLUSIONS: The changes in stress were significant only for the patients when exposed to cold ambient temperature, and only in patients, exposure to a cold ambient temperature significantly increased the risks of vascular aneurysm and damage to the brain tissue surrounding the blood vessels. These risks were found to be negligible for both healthy individuals and patients when exposed to hot ambient temperature and also for healthy individuals exposed to cold ambient temperature.

Finite element analysis of occlusal splint therapy in patients with bruxism.

BACKGROUND: Bruxism is among the habits considered generally as contributory factors for temporomandibular joint (TMJ) disorders and its etiology is still controversial. METHODS: Three-dimensional models of maxilla and mandible and teeth of 37 patients and 36 control subjects were created using in-vivo image data. The maximum values of stress and deformation were calculated in 21 patients six months after using a splint and compared with those in the initial conditions. RESULTS: The maximum stresses in the jaw bone and head of mandible were respectively 4.4 and 4.1 times higher in patients than in control subjects. Similar values for deformation were 5.8 and 4.9, respectively. The maximum stress in the jaw bone and head of mandible decreased six months after splint application by up to 71.0 and 72.8%, respectively. Similar values for the maximum deformation were 80.7 and 78.7%, respectively. Following the occlusal splint therapy, the approximation of maximum deformation to the relevant values in control subjects was about 2.6 times the approximation of maximum stress to the relevant values in control subjects. The maximum stress and maximum deformation occurred in all cases in the head of the mandible and the splint had the highest effectiveness in jaw bone adjacent to the molar teeth. CONCLUSIONS: Splint acts as a stress relaxer and dissipates the extra stresses generated as well as the TMJ deformation and deviations due to bruxism. The splint also makes the bilateral and simultaneous loading possible and helps with the treatment of this disorder through regulation of bruxism by creating a biomechanical equilibrium between the physiological loading and the generated stress.