Endoscopic third ventriculostomy: predicting outcome with phase-contrast MR imaging

Ventricular CSF proteomic profiles and predictors of surgical treatment outcome in chronic hydrocephalus

BACKGROUND

By applying an unbiased proteomic approach, we aimed to search for cerebrospinal fluid (CSF) protein biomarkers distinguishing between obstructive and communicating hydrocephalus in order to improve appropriate surgical selection for endoscopic third ventriculostomy vs. shunt implants. Our second study purpose was to look for potential CSF biomarkers distinguishing between patients with adult chronic hydrocephalus benefitting from surgery (responders) vs. those who did not (non-responders).

METHODS

Ventricular CSF samples were collected from 62 patients with communicating hydrocephalus and 28 patients with obstructive hydrocephalus. CSF was collected in relation to the patients' surgical treatment. As a control group, CSF was collected from ten patients with unruptured aneurysm undergoing preventive surgery (vascular clipping).

RESULTS

Mass spectrometry-based proteomic analysis of the samples identified 1251 unique proteins. No proteins differed significantly between the communicating hydrocephalus group and the obstructive hydrocephalus group. Four proteins were found to be significantly less abundant in CSF from communicating hydrocephalus patients compared to control subjects. A PCA plot revealed similar proteomic CSF profiles of obstructive and communicating hydrocephalus and control samples. For obstructive hydrocephalus, ten proteins were found to predict responders from non-responders.

CONCLUSION

Here, we show that the proteomic profile of ventricular CSF from patients with hydrocephalus differs slightly from control subjects. Furthermore, we find ten predictors of response to surgical outcome (endoscopic third ventriculostomy or ventriculo-peritoneal shunt) in patients with obstructive hydrocephalus.

Cine phase-contrast magnetic resonance imaging evaluation of cerebrospinal fluid flow dynamics in healthy pediatric subjects

Objective

To evaluate cerebrospinal fluid dynamics, using cine phase-contrast magnetic resonance imaging (cine-PC MRI), in healthy pediatric subjects, determining the normal flow values in this population, as well as identifying differences related to age, sex, and body surface area.

Materials and Methods

This was a descriptive cross-sectional study involving 32 healthy children and adolescents, in whom the flow of cerebrospinal fluid through the cerebral aqueduct was evaluated quantitatively with cine-PC MRI. We used specialized software to analyze the images obtained with cine-PC MRI, drawing a region of interest on the aqueduct. A flow-time curve was obtained, as were automated measurements of the various parameters.

Results

The following normal (mean) values were obtained: net flow, 1.10 ± 0.99 mL/m; stroke volume, 12.2 ± 10.1 µL/cycle; mean velocity, 0.72 ± 1.00 cm/s; peak systolic velocity, 5.28 ± 2.30 cm/s; peak diastolic velocity, 4.51 ± 1.77 cm/s. These values were not affected by age or sex. In addition, body surface area was not found to correlate significantly with mean velocity or stroke volume.

Conclusion

In children and adolescents, the basic cerebrospinal fluid flow parameters, as determined by cine-PC MRI, appear to be independent of age and sex.

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.

Usefulness of postoperative ventriculography and intracranial pressure monitoring following endoscopic third ventriculostomy

PURPOSE

The authors sought to determine whether the insertion of an external ventricular drain (EVD) at the time of surgery to monitor intracranial pressure (ICP) and ventriculography done within the first day following an endoscopic third ventriculostomy (ETV) is of benefit in postoperative patient management.

METHODS

Following IRB approval, ETV procedures done by the senior author between January 1, 2007, and December 31, 2016, were reviewed. Included in a consecutive fashion were all patients who underwent an ETV with placement of an external ventricular drain (EVD) that was preceded preoperatively by an MRI or CT study and followed by a contrast CT ventriculogram within the first postoperative day.

RESULTS

Identified were 72 patients who met the above criteria; however, technical ventriculography failure occurred in 4 (6%) and were eliminated from the analysis. Of the remaining 68 patients, contrasted CSF was seen in the basal cisterns/subarachnoid spaces (SAS) in 66 (97%) indicating a patent ETV and absent in 2 (3%) indicating a non-patent ETV. Of the 66 patients with a patent ETV, 34 (52%) patients were discharged on postoperative days 1 (8), 2 (13), and 3 (13) as their ICPs were not elevated and their clinical symptoms normal. EVDs placed at the time of the ETV recorded raised ICP > 20 cm H₂O in 17/68 (25%) patients for 1 or more days, all of whom had a patent ETV. Because of persistently elevated ICP requiring CSF drainage for control, 4 of these patients were shunted on postoperative days 5, 6, 6, and 10 and 3 with prolonged elevated ICP for 5, 6, and 11 days postoperatively were not shunted as their ICP and symptoms progressively normalized. The remaining 17/68 (25%) patients did not have a postoperative ICP > 20 cm H₂O; 14 were discharged after resolution of symptoms and other clinical factors, 1 was shunted on postoperative day 3 due to persistent symptoms and a consistently large volume of CSF drainage, and 2 had a non-patent ETV with 1 undergoing shunt placement and the other discharged because of the absence of symptoms. The sensitivity of ventriculography was only 13%; however, the specificity was 98% and the accuracy 88%.

CONCLUSION

After reviewing this series, the continued use of a postoperative EVD appears appropriate as the risk is low and it provides ventricular access to control ICP, thereby, improving patients' safety and reducing the need for CSF shunting on an urgent/emergent basis should the ETV prove to be unsuccessful. From our limited series, the usefulness of a 1-day postoperative ETV ventriculogram is less clear and would need confirmation with additional studies.

Imaging of cerebrospinal fluid flow: fundamentals, techniques, and clinical applications of phase-contrast magnetic resonance imaging

Cerebrospinal fluid (CSF) is a dynamic compartment of the brain, constantly circulating through the ventricles and subarachnoid space. In recent years knowledge about CSF has expended due to numerous applications of phase-contrast magnetic resonance imaging (PC-MRI) in CSF flow evaluation, leading to the revision of former theories and new concepts about pathophysiology of CSF disorders, which are caused either by alterations in CSF production, absorption, or its hydrodynamics. Although alternative non-invasive techniques have emerged in recent years, PC-MRI is still a fundamental sequence that provides both qualitative and quantitative CSF assessment. PC-MRI is widely used to evaluate CSF hydrodynamics in normal pressure hydrocephalus (NPH), Chiari type I malformations (CMI), syringomyelia, and after neurosurgical procedures. In NPH precisely performed PC-MRI provides reliable clinical information useful for differential diagnosis and selection of patients benefiting from surgical operation. Patients with CMI show abnormalities in CSF dynamics within the subarachnoid space, which are pronounced even further if syringomyelia coexists. Another indication for PC-MRI may be assessment of post-surgical CSF flow normalisation. The aim of this review is to highlight the significance of CSF as a multifunctional entity, to outline both the physical and technical background of PC-MRI, and to state current applications of this technique, not only in the diagnosis of central nervous system disorders, but also in the further clinical monitoring and prognosis after treatment.

Tales from the Night:: Emergency MR Imaging in Pediatric Patients after Hours

Overnight in-house radiology has rapidly become an important part of contemporary practice models, and is increasingly the norm in pediatric radiology. MR imaging is an indispensable first-line and problem-solving tool in the pediatric population. This has led to increasingly complex MR imaging being performed "after hours" on pediatric patients. This article reviews the factors that have led to widespread overnight subspecialty radiology and the associated challenges for overnight radiologists, and provides an overview of up-to-date imaging techniques and imaging findings of the most common indications for emergent MR imaging in the pediatric population.

Role of Secondary Endoscopic Third Ventriculostomy in Children: Review of an Institutional Experience

BACKGROUND

Endoscopic third ventriculostomy (ETV) has become a standard and safe procedure for obstructive hydrocephalus. ETV can also play an important role in children presenting with shunt malfunction with an added advantage of shunt independence. Secondary ETV can be defined as either a redo endoscopic ventriculostomy done after primary ETV stoma closure or that done in cases presenting with shunt malfunction.

OBJECTIVE

The aim of our study was to evaluate the role of secondary ETV in the pediatric age group patients.

METHODS

This is a retrospective analysis of 36 children (<18 years) who underwent ETV after shunt malfunction and 4 children with ETV done after previous ETV stoma closure from 2004 until 2018. In all patients, the obstructive pattern suggesting aqueduct outflow obstruction was observed on MRI. Patients were followed up for a mean period of 4.25 years.

RESULTS

ETV was considered successful if the patient avoided a shunt insertion later on in their life. Considering this definition, a success rate of 72% was observed with secondary ETV for shunt malfunction whereas a success rate of 75% was observed after primary ETV failure without any major side effects in any of the patients.

CONCLUSION

ETV can be considered a primary treatment modality in children with shunt malfunction and has a good success rate in cases presenting with closure of previously performed ETV stoma.

Radiofrequency saturation induced bias in aqueductal cerebrospinal fluid flow quantification obtained using two-dimensional cine phase contrast magnetic resonance imaging

PURPOSE

To explore the extent of bias in cerebrospinal fluid flow estimates due to radiofrequency saturation, and its possible impact on the use of two-dimensional cine phase contrast magnetic resonance imaging in the diagnosis and characterization of normal pressure hydrocephalus in patients.

THEORY AND METHODS

Theoretical signal equations were generated to describe saturation dependence on velocity. An experimental set of phase contrast magnetic resonance imaging scans with two different flip angles was used to show bias in flow estimates in a flow phantom, and in six different healthy volunteers. The cerebral aqueduct was targeted as the flow region of interest.

RESULTS

Data from a constant flow phantom showed a spatial distribution of voxels with significant bias in flow at the periphery of the flow region. The velocity difference (bias) maps of the cerebral aqueduct correlated with the spatial velocity gradients around peak systole and peak diastole, and high correlation with temporal velocity gradients during transition between systole and diastole. The aqueductal stroke volume for θ = 30° were found to be significantly higher than for θ = 10° using a Wilcoxon signed rank test.

CONCLUSION

This work shows the extent of bias in cerebrospinal fluid flow quantification due to radiofrequency saturation effects. This clinical relevance of this error was presented with respect to shunt responsiveness among normal pressure hydrocephalus patients. Magn Reson Med 79:2067-2076, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

Pediatric brain MRI, Part 2: Advanced techniques

Pediatric neuroimaging is a complex and specialized field that uses magnetic resonance (MR) imaging as the workhorse for diagnosis. MR protocols should be tailored to the specific indication and reviewed by the supervising radiologist in real time. Targeted advanced imaging sequences can be added to provide information regarding tissue microstructure, perfusion, metabolism and function. In part 2 of this review, we highlight the utility of advanced imaging techniques for superior evaluation of pediatric neurologic disease. We focus on the following techniques, with clinical examples: phase-contrast imaging, perfusion-weighted imaging, vessel wall imaging, diffusion tensor imaging, task-based functional MRI and MR spectroscopy.

Endoscopic Third Ventriculostomy in Children with Myelomeningocele: A Case Series

Hydrocephalus develops in up to 80-90% of children with myelomeningocele (MM) after closure of the defect. Traditionally, ventriculoperitoneal shunts have been used to manage hydrocephalus in these patients. A role for endoscopic third ventriculostomy (ETV) in MM has provoked much debate, principally due to anatomical variants described, which may complicate the procedure. We present 7 cases of children with MM and hydrocephalus undergoing a total of 10 ETV procedures. All patients demonstrated clinical improvement (in acute/subacute cases) or stabilization (in chronic cases). Three patients requiring a second ETV have shown clinical stability and renewed radiological evidence of functioning ventriculostomies in follow-up since reintervention. ETV can be used, albeit cautiously, in selected cases of hydrocephalus associated with MM. However, the frequency with which anatomical variation is encountered and the difficulty of the assessment of success make the procedure more challenging than usual.

MR-based measurements of portal vein flow and liver stiffness for predicting gastroesophageal varices

OBJECTIVES

We evaluated flow parameters measured by phase-contrast magnetic resonance (MR) imaging (PC-MRI) of the portal venous system and liver stiffness measured by MR elastography (MRE) to determine the usefulness of these methods in predicting gastroesophageal varices (GEV) in patients with chronic liver disease (CLD).

METHODS

In patients with CLD and controls, we performed PC-MRI on the portal (PV) and superior mesenteric veins; calculated mean velocity (V, cm/s), cross-sectional area (S, mm²), and flow volume (Q, mL/min); and determined markers of liver fibrosis (liver stiffness [kPa]) and aspartate aminotransferase (AST) platelet ratio index [APRI]). We visually assessed GEV and development of collateral pathways of the PV on routine contrast-enhanced dynamic MR imaging and compared patient characteristics, flow parameters, liver stiffness markers, and visual analysis among 3GEV groups, those with mild, severe, or no GEV with reference to endoscopic findings.

RESULTS

Child-Pugh grade, VPV, SPV, liver stiffness, APRI, and visually identified GEV (visible GEV) differed significantly among the 3 groups (P<0.05). We investigated VPV, SPV, liver stiffness, and visible GEV as independent markers to distinguish patients with and without GEV and examined VPV and visible GEV to predict severe GEV. Visible GEV showed low sensitivity (14 to 30%) and high specificity (98%) for predicting GEV in patients with CLD. A subgroup analysis that excluded cases with collateral pathway demonstrated slightly improved diagnostic performance of VPV and liver stiffness.

CONCLUSIONS

Portal vein flow parameters and liver stiffness can be useful markers for predicting GEV in patients with CLD.

Application of phase-contrast cine magnetic resonance imaging in endoscopic aqueductoplasty

The aim of this study was to evaluate the application of phase-contrast cine magnetic resonance imaging (MRI) in endoscopic aqueductoplasty (EA) for patients with obstructive hydrocephalus. The clinical diagnosis of hydrocephalus caused by aqueduct obstruction in 23 patients was confirmed by phase-contrast cine MRI examination. The patients were treated with EA and MRI was repeated during the follow-up. The cerebrospinal fluid (CSF) flow velocity in the aqueduct was measured to determine whether the aqueduct was obstructed. The results of phase-contrast cine MRI examinations indicated that there was no CSF flow in the aqueduct for all patients prior to surgery. Aqueductoplasty was successfully performed in all patients. The results of phase-contrast cine MRI examinations performed a week after surgery demonstrated an average CSF flow velocity of 4.74±1.77 cm/sec. During the follow-up, intracranial hypertension recurred in two patients in whom CSF flow was not observed in the aqueduct by the phase-contrast cine MRI scan. Aqueduct re-occlusion was revealed by an endoscopic exploration. By measuring the CSF flow velocity, phase-contrast cine MRI accurately identifies aqueduct obstruction. Cine MRI is a nontraumatic, simple and reliable method for determining whether the aqueduct is successfully opened following aqueductoplasty.

Why does endoscopic aqueductoplasty fail so frequently? Analysis of cerebrospinal fluid flow after endoscopic third ventriculostomy and aqueductoplasty using cine phase-contrast magnetic resonance imaging

OBJECT

The aim of this study was to evaluate and compare CSF flow after endoscopic third ventriculostomy (ETV) and endoscopic aqueductoplasty (EAP) in patients presenting with obstructive hydrocephalus caused by aqueductal stenosis.

METHODS

In patients harboring aqueductal stenosis who underwent EAP (n=8), ETV (n=8), and both ETV and EAP (n=6), CSF flow through the restored aqueduct and through the ventriculostomy was investigated using cine cardiac-gated phase-contrast MRI. For qualitative evaluation of CSF flow, an in-plane phase-contrast sequence in the midsagittal plane was used. The MR images were displayed in a closed-loop cine format. Quantitative through-plane measurements were performed in the axial plane perpendicular to the aqueduct and/or floor of the third ventricle.

RESULTS

Evaluation revealed significantly higher CSF flow through the ventriculostomies compared with flow through the aqueducts. This was true both when comparing the ETV group with the EAP group and when comparing the flow of the ventriculostomy and aqueduct within the ETV and EAP group. There was no difference in aqueductal CSF flow between patients who underwent EAP alone and patients who underwent ETV and EAP. There was also no difference in ventriculostomy CSF flow between patients who underwent ETV alone and patients who underwent ETV and EAP. Fifty percent of the restored aqueducts became occluded at a mean of 46 months after surgery (range 18-126 months). In contrast, all ETVs remained patent in the mean follow-up period of 110 months after surgery, although 1 patient required shunt placement after 66 months.

CONCLUSIONS

Cerebrospinal fluid flow through ventriculostomies is significantly higher than aqueductal CSF flow after EAP. This could be one factor to explain why the reclosure rate of aqueducts after EAP is higher than the reclosure rate of the ventriculostoma after ETV.

Decision support systems for clinical radiological practice -- towards the next generation

The huge amount of information that needs to be assimilated in order to keep pace with the continued advances in modern medical practice can form an insurmountable obstacle to the individual clinician. Within radiology, the recent development of quantitative imaging techniques, such as perfusion imaging, and the development of imaging-based biomarkers in modern therapeutic assessment has highlighted the need for computer systems to provide the radiological community with support for academic as well as clinical/translational applications. This article provides an overview of the underlying design and functionality of radiological decision support systems with examples tracing the development and evolution of such systems over the past 40 years. More importantly, we discuss the specific design, performance and usage characteristics that previous systems have highlighted as being necessary for clinical uptake and routine use. Additionally, we have identified particular failings in our current methodologies for data dissemination within the medical domain that must be overcome if the next generation of decision support systems is to be implemented successfully.