Advanced Imaging of Shunt Valves in Cranial CT Scans with Photon-Counting Scanner.

This brief report aimed to show the utility of photon-counting technology alongside standard cranial imaging protocols for visualizing shunt valves in a patient's cranial computed tomography scan. Photon-counting CT scans with cranial protocols were retrospectively surveyed and four types of shunt valves were encountered: proGAV 2.0®, M.blue®, Codman Certas®, and proSA®. These scans were compared with those obtained from non-photon-counting scanners at different time points for the same patients. The analysis of these findings demonstrated the usefulness of photon-counting technology for the clear and precise visualization of shunt valves without any additional radiation or special reconstruction patterns. The enhanced utility of photon-counting is highlighted by providing superior spatial resolution compared to other CT detectors. This technology facilitates a more accurate characterization of shunt valves and may support the detection of subtle abnormalities and a precise assessment of shunt valves.

Endovascular Shunting for Communicating Hydrocephalus Using a Biologically Inspired Transdural Cerebrospinal Fluid Valved eShunt® Implant.

Cerebrospinal fluid (CSF) bathing the central nervous system is produced by brain and choroid plexus within the ventricles for re-absorption into the venous circulation through arachnoid granulations (AG). Communicating hydrocephalus results from disruption of the absorptive process, necessitating surgical catheter-based shunt placement to relieve excess pressure from CSF buildup. Adjustable valve designs and antibiotic impregnation have minimally impacted persistent failure rates and postoperative complications. To confront this challenge, we have developed an innovative endovascular shunt implant biologically inspired from AG function to restore the natural dynamics of CSF drainage while concurrently addressing the predominant factors contributing to conventional shunt malfunction.

Multimodal radionuclide shuntography for device patency: New procedural tips for anuncommon historical technique.

Cerebrospinal fluid (CSF) shunting is an established long-term treatment option for hydrocephalus, and is one of the most commonly performed neurosurgical procedures in western countries.Despite advances in CSF shunt design and management, its failure rates remain high and is most commonly due to obstruction and infection.Cerebrospinal fluidshunt failure diagnosis should be prompt and accurate in establishing timely if its revision is appropriate. Radionuclide shuntography with technetium-99m-diethylenetriaminepetaacetic acid (99mTc-DTPA) is a useful technique for evaluation CSF shunts and management of patients presenting with shunt-related problems, in particular it can avoid unnecessary replacement interventions. Although its execution and interpretation require specific skills, we suggest its execution for the evaluation of device's patency. We here describe the radionuclide shuntography performed with recent hybrid multimodal technologies, with a procedure customized to a complicated patient with hydrocefalus and neoplastic disease. We suggest considering radionuclide shuntography in association with conventional imaging and strongly recommend the additional performance of single photon emission computed tomography/computed tomography (SPECT/CT) because it also provides valuable information to complete the interpretation of planar images.

Safety and function of programmable ventriculo-peritoneal shunt valves: An in vitro 7 Tesla magnetic resonance imaging study.

OBJECTIVE: The quantity of ultra-high field MRI neuroimaging studies has rapidly increased. This study tests function, safety, and image artifacts of two frequently implanted programmable ventriculo-peritoneal (VP) shunt valves in a 7T MRI system. METHODS: All tests were performed using a whole-body 7T MRI system. Three proGAV 2.0 and 3 CODMAN CERTAS® Plus programmable VP-shunt valves were tested in three steps. 1) Deflection angle tests close to the bore opening at the location of a static magnetic field gradient of 3-5 T/m. 2) Valves were fixed on a spherical phantom in 3 positions (a. lateral, b. cranial, c. cranial with 22.5° tilt anteriorly) and assessed for keeping the programmed pressure setting and reprogrammability. 3) Valves were fixed on the phantom and positioned lateral in a radiofrequency head coil. MRI scans were performed for both models, including MPRAGE, GRE and SE sequences. RESULTS: Deflection angles were moderate (13°, 14°, 13°) for the proGAV valves and close to critical (43°, 43°, 41°) for the CODMAN valves at the test location. Taking a scaling factor of 2-3 for the maximum spatial magnetic field gradient accessible to a patient within the magnet bore into account renders both valves MR unsafe regarding ferromagnetic attraction. The proGAV valves kept the pressure settings in all positions and were reprogrammable in positions a. and b. In position c., reprogrammability was lost. The CODMAN valves changed their pressure setting and reprogrammability was lost in all positions. MR image signal homogeneity was unaltered in the phantom center, artifacts limit the assessability of structures in close vicinity to the valves. CONCLUSION: Both tested programmable VP-shunt valves are MR unsafe for 7T systems. Novel programming mechanisms using permanent magnets with sufficient magnetic coercivity or magnet-free mechanisms may allow the development of programmable VP-shunt valves that are conditional for 7T MR systems.

Hydrocephalus Study Design: Testing New Hypotheses in Clinical Studies and Bench-to-Bedside Research.

In this article, we aimed to describe some of the currently most challenging problems in neurosurgical management of hydrocephalus and how these can be reasons for inspiration for and development of research. We chose 4 areas of focus: 2 dedicated to improvement of current treatments (shunt implant surgery and endoscopic hydrocephalus surgery) and 2 dedicated to emerging future treatment principles (molecular mechanisms of cerebrospinal fluid secretion and hydrocephalus genetics).

Evaluation of smartphone-integrated magnetometers in detection of safe electromagnetic devices for use near programmable shunt valves: a proof-of-concept study.

OBJECTIVE: External magnetic forces can have an impact on programmable valve mechanisms and potentially alter the opening pressure. As wearable technology has begun to permeate mainstream living, there is a clear need to provide information regarding safety of these devices for use near a programmable valve (PV). The aim of this study was to evaluate the magnetic fields of reference devices using smartphone-integrated magnetometers and compare the results with published shunt tolerances. METHODS: Five smartphones from different manufacturers were used to evaluate the magnetic properties of various commonly used (n = 6) and newer-generation (n = 10) devices using measurements generated from the internal smartphone magnetometers. PV tolerance testing using calibrated magnets of varying field strengths was also performed by smartphone magnetometers. RESULTS: All tested smartphone-integrated magnetometers had a factory sensor saturation point at around 5000 µT or 50 Gauss (G). This is well below the threshold at which a magnet can potentially deprogram a shunt, based on manufacturer reports as well as the authors' experimental data with a threshold of more than 300 G. While many of the devices did saturate the smartphone sensors at the source, the magnetic flux density of the objects decreases significantly at 2 inches. CONCLUSIONS: The existence of an upper limit on the magnetometers of all the smartphones used, although well below the published deprogramming threshold for modern programmable valves, does not allow us to give precise recommendations on those devices that saturate the sensor. Based on the authors' experimental data using smartphone-integrated magnetometers, they concluded that devices that measure < 40 G can be used safely close to a PV.

Standardization of cerebrospinal fluid shunt valves in pediatric hydrocephalus: an analysis of cost, operative time, length of stay, and shunt failure.

OBJECTIVE: CSF shunts are the most common procedures performed in the pediatric neurosurgical population. Despite attempts in multiple studies, a superior shunt valve has never been shown. Because of this, the authors aim was to examine the impact of shunt valve standardization at their institution to determine if there is a difference in surgical cost, operative time, or short-term postoperative shunt failure. METHODS: A retrospective analysis at the authors' institution was performed for all new CSF diversion shunts, as well as shunt revisions requiring a new valve, or a new valve and at least a new proximal or distal catheter over a 1-year period (January 1, 2016, to December 31, 2016). After a period of transition, neurosurgeons were encouraged to use only one type of fixed-differential-pressure valve and one type of programmable valve when performing shunt surgeries. These patients who underwent "standardized" shunt surgery over a 1-year period (January 1, 2018, to December 31, 2018) were then compared to patients in the prestandardization epoch. All patients were followed for a 12-month period after surgery. Demographic information, surgical cost, operative time, and postoperative shunt failure data were collected in all patients in the study. RESULTS: The authors analyzed 87 shunt surgeries in patients prior to standardization and 94 shunt surgeries in patients after standardization. The rate of violation of the standardized shunt valve policy after implementation was 5.3% (5 of 94 procedures). When comparing the prestandardization group to those who received the standardized valve, operative costs were less ($1821.04 vs $1333.75, p = 0.0034). There was no difference in operative times between groups (78 minutes vs 81 minutes, p = 0.5501). There was no difference in total number of shunt failures between the two groups at 12 months after surgery (p = 0.0859). The rate of postoperative infection was consistent with the literature at 8%. CONCLUSIONS: In accordance with quality improvement principles, the reduction of unexplained clinical variance invariably leads to a decrease in cost and, more importantly, increased value. In this study, the implementation of a standardized shunt valve decreased operative cost. There were no differences in postoperative shunt failures at 12 months after surgery and no differences in length of surgery. Standardizing shunt valves in the treatment of pediatric hydrocephalus seems to be cost-effective and safe.

Evaluating the Effects of Cerebrospinal Fluid Protein Content on the Performance of Differential Pressure Valves and Antisiphon Devices Using a Novel Benchtop Shunting Model.

BACKGROUND: Hydrocephalus is managed by surgically implanting flow-diversion technologies such as differential pressure valves and antisiphoning devices; however, such hardware is prone to failure. Extensive research has tested them in flow-controlled settings using saline or de-aerated water, yet little has been done to validate their performance in a setting recreating physiologically relevant parameters, including intracranial pressures, cerebrospinal fluid (CSF) protein content, and body position. OBJECTIVE: To more accurately chart the episodic drainage characteristics of flow-diversion technology. A gravity-driven benchtop model of flow was designed and tested continuously during weeks-long trials. METHODS: Using a hydrostatic pressure gradient as the sole driving force, interval flow rates of 6 valves were examined in parallel with various fluids. Daily trials in the upright and supine positions were run with fluid output collected from distal catheters placed at alternating heights for extended intervals. RESULTS: Significant variability in flow rates was observed, both within specific individual valves across different trials and among multiple valves of the same type. These intervalve and intravalve variabilities were greatest during supine trials and with increased protein. None of the valves showed evidence of overt obstruction during 30 d of exposure to CSF containing 5 g/L protein. CONCLUSION: Day-to-day variability of ball-in-cone differential pressure shunt valves may increase overdrainage risk. Narrow-lumen high-resistance flow control devices as tested here under similar conditions appear to achieve more consistent flow rates, suggesting their use may be advantageous, and did not demonstrate any blockage or trend of decreasing flow over the 3 wk of chronic use.

In vitro performance of combinations of anti-siphon devices with differential pressure valves in relation to the spatial position.

BACKGROUND: Programmable differential pressure (DP) valves combined with an anti-siphon device (ASD) represent the current standard of care in preemtping overdrainage associated with ventriculoperitoneal shunting for hydrocephalus. OBJECTIVE: We aimed to provide comparative data of four combinations of two ASDs of different working principles in combination with two DP valves in an in vitro model in order to achieve a better understanding of the flow characteristics and potential clinical application. METHODS: We analyzed the flow performance of four possible combinations of two DP valves (CHPV [HM]; proGAV 2.0[PG]) in combination with either a gravity-regulated (Shuntassistant [SA]) or a flow-regulated (SiphonGuard [SG]) ASD in an in vitro setup. A DP between 4 and 60 cmH2O was generated, and the specific flow characteristics were measured. In addition, the two combinations with gravity-regulated ASDs were measured in defined spatial positions. RESULTS: Flow characteristics of the SA combinations corresponded to the DP in linear fashion and to the spatial position. Flow characteristics of the SG combinations were dependent upon the DP in a non-linear fashion and independent of the spatial position. Highest mean flow rate of the PG-SG- (HM-SG-) combination was 1.41 ± 0.24 ml/min (1.16 ± 0.06 ml/min). The mean flow rates sharply decreased with increasing inflow pressure and subsequently increased slowly up to 0.82 ± 0.26 ml/min (0.77 ± 0.08 ml/min). CONCLUSION: All tested device combinations were able to control hydrostatic effect and prevent consecutive excessive flow, to varying degrees. However, significant differences in flow characteristics can be seen, which might be relevant for their clinical application.

Persistent shunt dependency in children treated with CSF diversion for idiopathic intracranial hypertension (IIH).

Long-term shunt dependency rates in children treated for IIH with CSF diversion have not been established. We therefore present our experience with 4 children shunted for Idiopathic Intracranial Hypertension (IIH) during the years 1988-2000 with very long-time follow-up. Two out of these patients have experienced late or very late episodes of severe shunt failure during the second or third decade after initial shunt treatment. They were all boys and may not be representative for IIH patients as a whole. Two of them appear, however, to be permanently shunt dependent, indicating that long-term shunt dependency in children treated for IIH with CSF diversion may be more common than previously expected.

Safety and Efficacy of Syringoperitoneal Shunting with a Programmable Shunt Valve for Syringomyelia Associated with Extensive Spinal Adhesive Arachnoiditis: Technical Note.

OBJECTIVE: Although syringomyelia associated with extensive spinal adhesive arachnoiditis (SAA) can be a progressive disease that has potentially devastating clinical consequences, its surgical resolution has remained poorly defined. The aim of the present study was to verify the safety and efficacy of syringoperitoneal shunting for syringomyelia associated with extensive SAA. METHODS: The present retrospective study included 15 patients who had undergone syringoperitoneal shunting with a programmable shunt valve for the diagnosis of syringomyelia associated with extensive SAA from October 2012 to June 2018. The shunt pressure was appropriately adjusted according to the postoperative sequential clinical condition and change in syringomyelia evaluated using magnetic resonance imaging. The average postoperative follow-up duration was 32.7 months. RESULTS: No surgery-related complications such as shunt dysfunction or infection occurred during the follow-up period, except for 2 patients with minor issues with the shunt tube. The average shunt pressure at the last follow-up examination was 4.5 cm H2O. The findings from the clinical assessment suggested that the average grade on the sensory pain scale was 2.9 before surgery and had improved significantly to 2.5 at the most recent follow-up examination. Radiological analysis suggested that improvement of syringomyelia was noted in 14 of the 15 patients (93.3%), with no cases of radiological aggravation. No recurrence of syringomyelia developed during the follow-up period in the present study. CONCLUSION: Syringoperitoneal shunting with a programmable shunt valve was safe and effective for clinical control of syringomyelia associated with extensive SAA. Long-term follow-up is mandatory to monitor for shunt dysfunction and mechanical trouble.

An [18F]-Positron Emitting Fluorophore Allows Safe Evaluation of Small Molecule Distribution in the CSF, CSF Fistulas, and CNS Device Placement.

The small molecule fluorescein is commonly used to guide the repair of cerebral spinal fluid leaks (CSFLs) in the clinic. We modified fluorescein so that it is also visible by positron emission tomography (PET). This probe was used to quantitatively track the fast distribution of small molecules in the CSF of rats. We tested this probe in models relevant to the clinical diagnosis and treatment of central nervous system (CNS) diseases that affect CSF flow. In this study, fluorescein was radiolabeled with fluorine-18 to produce Fc-AMBF3. [18/19F]-Fc-AMBF3 was introduced at trace quantities (13.2 nmols, 100 µCi) intrathecally (between L5 and L6) in rats to observe the dynamic distribution and clearance of small molecules in the CSF by both [18F]-PET and fluorescence (FL) imaging. Murine models were used to demonstrate the following utilities of Fc-AMBF3: (1) utility in monitoring the spontaneous CSFL repair of a compression fracture of the cribriform plate and (2) utility in quantifying CSF flow velocity during neurosurgical lumboperitoneal shunt placement. Fc-AMBF3 clearly delineated CSF-containing volumes based on noninvasive PET imaging and in ex vivo FL histology. In vivo morbidity (n = 16 rats, <2.7 mg/kg, 77 times the PET dose) was not observed. The clearance of the contrast agent from the CNS was rapid and quantitative (t1/2 = 33.8 ± 0.6 min by FL and t1/2 = 26.0 ± 0.5 min by PET). Fc-AMBF3 was cleared from the CSF through the vasculature and/or lymphatic system that supplies the cribriform plate and the temporal bone. Fc-AMBF3 can be used to diagnose CSFLs, image CSFL repair, and determine the CSF flow velocity in the CNS or through lumboperitoneal shunts by PET/FL imaging. In conclusion, Fc-AMBF3 PET imaging has been demonstrated to safely and dynamically quantitate CSF flow, diagnose fistulas associated with the CSF space, and approximate the clearance of small molecules in the CSF.

Snap-valve cerebral shunt design for intracranial pressure operation and ultrasound visualization.

Cerebral spinal fluid (CSF) shunts are the main treatment for hydrocephalus. They divert excess CSF from the ventricular system to the abdominal, pleural, or intravascular space where it is absorbed. The shunt valve regulates flow based on intracranial pressure (ICP) to maintain a physiologically stable and safe ICP. Shunt malfunction is difficult to detect, life-threatening and common. The present study demonstrates that snap-though buckling (STB) shells can be transformed into pressure-relief valves that act in the normal physiological range of ICP. Three different shell designs in this preliminary experiment were found to have opening and closing pressures that fall within the physiologically normal range of ICP of 6 to 25 cm H2O. Furthermore, these STB shells demonstrate a valve actuation that is visible by ultrasound and have an implantable form-factor that is similar to currently available shunt valves. The unique characteristics of STB shell valves have potential clinical applications for shunt monitoring using ultrasound imaging and can be fabricated from antibiotic-impregnated materials to mitigate shunt infection. These characteristics make STB valves attractive for future use in cerebral shunt systems.

Port-a-cath and ventriculoatrial shunt at the same atrium: technical note.

Hydrocephalus is a rare complication of brain involving acute lymphoblastic leukemia (ALL). The standard treatment is ventriculoperitoneal (VP) shunting, while ventriculoatrial (VA) shunting is the second option in a case of VP shunt failure in young children. But the presence of port catheter at the right atrium restricts and makes a VA shunt difficult to place in the same atrium. We presented a 4-year-old boy who had the diagnoses of ALL and underwent chemotherapy through a port-a-cath. He also had hydrocephalus due to the brain invasion of the ALL. He firstly underwent VP shunting for the treatment of hydrocephalus, but it failed due to an intraabdominal cyst. Then, he underwent VA shunting through the left internal jugular vein. This is the first case in the literature showing both catheters in the right atrium.

Anatomical characterization of the inferior petrosal sinus and adjacent cerebellopontine angle cistern for development of an endovascular transdural cerebrospinal fluid shunt.

BACKGROUND AND PURPOSE: We evaluated the inferior petrosal sinus (IPS) and adjacent cerebellopontine angle (CPA) cistern as a potential implantation site for a novel venous endovascular transdural CSF shunt concept to treat communicating hydrocephalus. We analyzed the dimensions of the IPS, CPA cistern, and distances to adjacent neurovascular structures. MATERIALS AND METHODS: Gadolinium enhanced T1 weighted brain MRI datasets of 36 randomly selected patients, aged 20-80 years, were analyzed with three-dimensional multiplanar reconstruction to measure IPS diameter and length, CPA cistern depth, and IPS proximity to the vertebrobasilar arteries and brainstem. Statistical analysis was used to assess gender, sidedness, and age dependence. RESULTS: Mean IPS diameter ranged from 2.27 mm to 3.31 mm at three axial levels, with >90% larger than 1.46 mm. CPA cistern adjacent to the IPS exhibited a mean depth of 3.86 mm to 7.39 mm between the dura and brainstem at corresponding axial levels. There was no side dependence except for a longer distance from the IPS to the basilar artery on the left compared with the right (9.72 vs 7.28, P<0.019). Linear regression analysis showed that the distance from the IPS to the brainstem was statistically significantly increased with age (P<0.0002) and was greater in men, with little side variation (P=0.524). CONCLUSION: Our results demonstrate sufficient CSF CPA cisternal space adjacent to the IPS and support the feasibility of an endovascular catheter delivered transdural implantable shunt. Such a device could serve to mimic the function of the arachnoid granulation by establishing a regulated path for CSF flow from the intracranial subarachnoid space to the venous system and provide a treatment for communicating hydrocephalus.

"Reverse J Shaped " Skin Flap and Cranial Bone Groove for Shunt Hardware: A New Technique for Patients with Fragile Skin.

Shunt systems are not perfect devices and can cause severe complications. Complications may originate from problems related to the valve, the patient, or the surgery and are more common in neonates, infants, especially preterm, by reason of the special characteristics of these patients. We, therefore, have successfully developed a useful and viable surgical technique in order to provide helpful aspects to the surgical issues mentioned above. This technique includes a "reverse J shaped" skin incision nonintersecting the shunt's hardware and distal catheter to reduce wound problems to a minimum by opening a "bone groove". We believe that the above technique described by us will both reduce issues such as scalp ulceration, wound dehiscence, and shunt exposure in premature and pediatric hydrocephalus cases with a friable scalp, and eliminate a cosmetic problem in hydrocephalic patients of all ages.

Fluoroscopic-Guided Paramedian Approach for Lumbar Catheter Placement in Cerebrospinal Fluid Shunting: Assessment of Safety and Accuracy.

BACKGROUND: Spinal catheter insertion in lumboperitoneal (LP) shunt surgery for idiopathic normal pressure hydrocephalus (iNPH) is frequently associated with technical difficulties especially in patients with obesity and elderly patients with vertebral deformities. OBJECTIVE: To elucidate the accuracy and safety of image-guided spinal catheter placement using a paramedian approach (PMA). METHODS: We retrospectively analyzed 39 consecutive iNPH patients treated by LP shunting with spinal catheter insertion via the PMA. The success rate of catheter placement and the number of changes in puncture location were evaluated. Accuracy of catheter insertion was assessed by measuring both vertical and horizontal deviations in the point of catheter dural penetration from the center of the interlaminar space. RESULTS: The success rate of catheter placement was 100% (39/39). The difficulty rate for catheter insertion, measured by the number of changes in puncture location, was 2.6% (1/39). No bloody punctures or surgical infections were observed. Accuracy of catheter insertion, measured as the degree of deviation, was 0.5 ± 1.9 mm horizontally and 0.0 ± 2.4 mm vertically. The rates of minor complications, including caudal catheter insertion, transient low-pressure headache, and root pain, were 5.1% (2/39), 10.4% (4/39), and 0% (0/43), respectively. Subdural hematoma requiring surgical intervention occurred in 1 case (2.6%). During the mean follow-up period of 36 mo, spinal catheter rupture at the level of the spinous processes was not observed. CONCLUSION: Fluoroscopic-guided spinal catheter placement via the PMA was safe, accurate, and reliable, even for use in geriatric and obese patients.

A new dynamic model for in vitro evaluation of intravascular devices.

INTRODUCTION:: A dynamic model to evaluate thrombus formation on intravascular catheters in vitro is presented. The model enables fluid infusion, variation in the catheter orientation, and variable flow conditions. It was applied on a catheter used to shunt cerebrospinal fluid to a vein, a dural venous sinus, for the treatment of hydrocephalus. METHODS:: Fresh human blood-filled circuits were circulated in a non-occlusive roller pump. A catheter infused either with cerebrospinal fluid, Ringer's lactate, or no fluid (control) was inserted through each circuit's wall. Sixteen circuits (six cerebrospinal fluid, six Ringer's lactate, four control) ran for 60 min. Qualitative assessment was performed by measuring viscoelastic properties of blood at the start and end of the experiment; quantitative evaluation of clot formation by scanning electron microscope. RESULTS:: Average blood velocity was 79 mm/s, with a pressure wave between 5 and 15 mm Hg. At the experiment's end, the infused fluid represented 5.88% of the blood/infusion volume in the circuit. The control circuits showed no statistical difference between the start and end for viscoelastic testing, whereas both Ringer's lactate and cerebrospinal fluid enhanced coagulation, most pronounced for the latter. Most thrombus material was observed on catheters in the cerebrospinal fluid group. Clot formation was less pronounced on the surface of the catheter facing the blood flow. DISCUSSION:: A dynamic model for intravascular catheter testing mimics better clinical conditions when evaluating blood-material interaction. Catheter position, blood flow around the catheter, and infusion fluid all have a potential impact on the hemocompatibility of a given catheter.