- Email: [email protected]
Diagnosis of Ventriculoperitoneal Shunt Malfunction: A Practical Algorithm
Journal Pre-proof Diagnosis of ventriculo-peritoneal shunt malfunction: a practical algorithm Morgan Broggi, M.D., Ph.D., Costanza M. Zattra, M.D., Marco Schiariti, M.D., Francesco Acerbi, M.D., Ph.D., Giovanni Tringali, M.D., Jacopo Falco, M.D., Laura G. Valentini, M.D., Giuseppe Faragò, M.D., Paolo Ferroli, M.D., Giovanni Broggi, M.D. PII:
S1878-8750(20)30265-5
DOI:
https://doi.org/10.1016/j.wneu.2020.02.003
Reference:
WNEU 14277
To appear in:
World Neurosurgery
Received Date: 9 November 2019 Revised Date:
31 January 2020
Accepted Date: 1 February 2020
Please cite this article as: Broggi M, Zattra CM, Schiariti M, Acerbi F, Tringali G, Falco J, Valentini LG, Faragò G, Ferroli P, Broggi G, Diagnosis of ventriculo-peritoneal shunt malfunction: a practical algorithm World Neurosurgery (2020), doi: https://doi.org/10.1016/j.wneu.2020.02.003. This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2020 Elsevier Inc. All rights reserved.
Diagnosis of ventriculo-peritoneal shunt malfunction: a practical algorithm Morgan Broggi1 M.D., Ph.D., Costanza M. Zattra1 M.D., Marco Schiariti1 M.D., Francesco Acerbi1 M.D., Ph.D., Giovanni Tringali1 M.D., Jacopo Falco1 M.D., Laura G. Valentini1 M.D., Giuseppe Faragò2 M.D., Paolo Ferroli1 M.D., and Giovanni Broggi1 M.D. 1
Department of Neurosurgery, and 2Diagnostic Radiology and Interventional Neuroradiology Unit,
Fondazione IRCCS Istituto Neurologico Carlo Besta, Milano, Italy
Corresponding author: Morgan Broggi, M.D., Ph.D. Department of Neurosurgery Fondazione IRCCS Istituto Neurologico Carlo Besta Via Celoria, 11; 20133, Milano, Italy Tel: +39 02 23942411 Fax: + 39 02 70635017 Email: [email protected]
Keywords: Hydrocephalus; Ventriculo-peritoneal shunt; CSF shunt; Shunt malfunction; Ventriculo-peritoneal shunt revision.
Short Title: VPS malfunction: a diagnostic algorithm.
1
ABSTRACT: Objective: This study aims to present a practical method to accurately diagnose ventriculoperitoneal shunt (VPS) malfunction and to detect the exact level at which the system has failed in order to tailor VPS revision at that level only. Methods: A tertiary-referral, single-center algorithm for diagnosis of VPS malfunction is proposed. Based on clinical symptoms and confirmed ventricular dilatation on computed tomography, the VPS reservoir is punctured: if no cerebrospinal fluid (CSF) is obtained, ventricular catheter replacement is recommended. Conversely, if CSF is obtained, a sample is sent for cultural exam and the macroscopic integrity of the whole system is checked via plain x-rays in the angiographic suite. Then, through the injection of iodate contrast medium into the reservoir and selective exclusion of the proximal and distal catheters, the patency and correct VPS functioning are investigated. Results: 102 (56 males, mean age 41.5, range 1-86) patients underwent VPS function test from 2012 to 2018: 59 (57.8%) cases of VPS malfunction were diagnosed. Ventricular catheter obstruction/damage/displacement occurred in 12/59 (20.3%) cases, valve damage in 11/59 (18.6%) cases, distal catheter obstruction/damage/displacement in 17/59 (28.8%) cases and two-levels (valve/proximal catheter or valve/distal catheter) obstruction/damage/displacement in 16/59 (27.1%) cases. Subclinical infection was diagnosed in 3 patients (5.1%). VPS revision was performed selectively at the level of failure. Conclusions: The proposed algorithm is a practical, simple and minimally-invasive technique to accurately diagnose VPS malfunction, identifying the exact level of system failure and allows to tailor surgical VPS revision, avoiding unnecessary complete system replacement.
2
MANUSCRIPT:
Introduction: Hydrocephalus is defined as a pathologic accumulation of cerebrospinal fluid (CSF) in the brain or, more precisely, an active distension of the ventricular system resulting from inadequate passage of CSF from its point of production to its point of absorption.1 It is a relatively common condition, with an estimated 69,000-related hospital discharges reported annually and a mean prevalence of 85/100,000 in the United States.2,3 An established long-term treatment option for hydrocephalus is CSF shunting. It consists most of the times of a ventriculo-peritoneal shunt (VPS),4 while rarely the distal catheter is placed in the right heart atrium. VPS is one of the most commonly performed neurosurgical procedures with an estimated incidence of approximately 5.5 per 100,000 in the U.S.5 However, despite being considered a low risk procedure and regardless advances in shunts design and management, malfunction rates remain high, with approximately 40% of pediatric shunts and 29% of adult shunts failing in the first year of placement and 45-81% of shunt patients requiring at least one surgical shunt revision in their lifetime.6,7 While in the adult so-called normal pressure hydrocephalus (NPH) most VPS malfunctions concern the distal peritoneal catheter, in children proximal ventricular catheter obstruction/malfunction is more common.2,8 Another valid treatment option for hydrocephalus is represented by endoscopic third ventriculostomy; although it may be applied also to communicating hydrocephalus,9 its best results were achieved in treating obstructive hydrocephalus.10 This procedure is considered to have a very low risk profile11 and, especially, it does not carry the risk of “system malfunction”, since no device is implanted. VPS malfunction, on the other hand, can lead to severe consequences with increased morbidity and mortality12 and for this reason, its diagnosis should be prompt and accurate and should be followed by timely VPS revision.13,14 Nevertheless, despite several techniques have been proposed,8,12,15–19 correct recognition of shunt failure is challenging and no consensus guidelines or recommended approach to diagnostic imaging exist nowadays.17 Moreover, the exact segment of system failure (proximal catheter, valve device or distal catheter) is rather tough to identify and, yet again, no standardized method has been approved. The aim of this study is to propose a quick and practical algorithm to easily diagnose VPS malfunction and identify the exact point of system failure in order to address the surgical intervention on the segment actually requiring revision.
3
Methods: A retrospective tertiary referral center study was conducted from January 1st, 2012 to December 31st, 2018 on all shunt patients admitted for symptoms suspicious for VPS failure and who underwent a VPS function test. Our Institute has been deeply committed to the management of hydrocephalus, both pediatric and adult, for more than forty years and outstanding colleagues published the first version of the algorithm used to disclose shunt malfunction.20 Following on that experience, the procedure was revised and ameliorated several times until the approval of the present version, which has been used over the last 10 years. In 2004 the Institutional Ethical Board formally approved this method. Once a patient with a VPS complains of clinical symptoms that are suggestive of system failure, he/she is admitted to the outpatient hospital service and a dedicated protocol is applied. First things first, a clinical examination is carried out, preferably by a neurologist/neurosurgeon who is familiar with the patient and his/her clinical history so that even the slightest neurological changes between preoperative, early postoperative and present status are easier to detect. This examination should also include a simple valve reservoir palpation to look for its rapid reexpansion in order to rule out ventricular catheter obstruction/malfunction; the presence of some “red flags”, like gait imbalance, disorientation, drowsiness, ocular movement deficits (e.g. Parinaud syndrome), nuchal rigidity, meningism and, in general, any worsening of the previous neurological status, should be noted as well. If there is a strong suspicion of hardware infection (e.g. high fever, bad wound healing, skin CSF leakage, et cetera), besides ordering routine blood tests, a shunt tap is performed and CSF is sent for urgent microbiological examination; in these cases, VPS function test is postponed until the test results are back. Following clinical examination, a brain Computed Tomography (CT) scan without intravenous contrast administration is performed: besides comparing ventricles dimensions to previous scans (i.e. when the VPS was supposed to work properly),19 other complications such hyper-drainage with/without subdural collections, hemorrhages and ventricular catheter dislocation are ruled out (Fig. 1A). It is important to underline that the CT is performed mainly to exclude the latter rather than to look strictly at the ventricles’ dimensions; in other words, apart from significant changes in the ventricles size, this aspect is not considered of high importance in the diagnostic process of VPS malfunction. If the CT does not show increased ventricles size and infection is not suspected, the valve opening pressure is modified (no more than 20-40 mmH2O), the patient is discharged and a
4
follow-up visit is planned within 2-4 weeks: if there is clinical improvement, no other recommendations are suggested. Conversely, if the CT scan does show enlarged ventricles compared to previous scans or if there is no clinical improvement at the follow-up appointment, the valve reservoir is firstly pumped and secondly punctured in a sterile manner. If the reservoir does not re-expand and/or no CSF is obtained from the puncture there is a strong suspicion for proximal catheter obstruction/failure and its surgical replacement is indicated. Intraoperatively, after the new catheter is inserted, it is recommended to test both the correct function of the valve and the distal catheter. The former is assessed just connecting the valve to the new proximal catheter and pumping the reservoir, while the latter is checked by draining, through the peritoneal catheter, 10-20 ml of saline solution under hydrostatic pressure or under slight manual pressure. If otherwise CSF is easily tapped from the reservoir, a sample is sent for dosage of CSF proteins level and microbial exam and the patient is transferred to the angiographic suite. Here, initially the integrity of the whole system is checked via a plain radiograph “shunt series” (Fig. 1B) and then, in a sterile manner, the actual VPS function test is conducted (Fig. 2A). The aim of this test is to selectively examine the performance of each segment of the system: first of all, the proximal catheter is (re)checked. This is done because in case of partial obstruction CSF can sometimes be tapped from the reservoir (see above). While the distal catheter is manually closed few cm distal to the valve, the reservoir is punctured, and 3-4 ml of a solution composed by saline and iodate contrast medium (1:1) are gently injected (Fig. 2B). The patency of the proximal catheter is confirmed on the angiographic screen by a homogenous filling of the ventricle with contrast medium (Fig. 2C). If this does not happen or it is hard to inject the solution, proximal complete or partial obstruction should be suspected. Secondly, the valve and the distal catheter are assessed; the proximal catheter is now closed by applying some pressure just before the valve, as described above, and 5-7 ml of a solution composed by saline and iodate contrast medium (1:1) are gently injected (Fig. 2D). The patency of the distal catheter is confirmed on the angiographic screen by a typical “puff” of contrast medium exiting the catheter in the abdomen (Fig. 2E). If this happens, a whole system re-evaluation is recommended and, in specific situations (e.g. insufficient intraperitoneal CSF absorption in patients with multiple previous abdominal surgeries), entire VPS revision or ventriculo-atrial shunt should be considered. Conversely, if the contrast does not reach the abdomen with evidence of integrity and regular course of the distal catheter, a valve malfunction should be suspected and its surgical selective replacement with intraoperative functional test of the proximal and distal catheters (see above) is recommended. Otherwise, if the
5
contrast stops somewhere along the distal catheter, it is likely that the catheter is obstructed or damaged (sometimes an actual leakage of contrast is shown on the angiographic screen, Fig. 2F). The only absolute contraindication for the function test was known allergy to iodate contrast medium. It should be stressed that the injection of the saline/contrast solution should be made by an experienced neurosurgeon in order to prevent complications such as valve damages or multiple reservoir punctures with increased infection risks. The whole process takes few hours (usually less than 4) and, if diagnosis of shunt malfunction is confirmed, the patient is admitted to the hospital ward to undergo shunt revision, which is usually performed on the very same day. The algorithm is schematized in Figure 3. All patients included in the study gave written consent for demographic, clinical and radiological data review and publication.
Results: One hundred and two patients (56 males, 46 females, mean age 41.5, range 1-86 years old (y.o.)) underwent VPS function test as described above in the last seven years (2012-2018). There were 79 (77.5%) adult (>18 y.o.) and 23 (22.5%) pediatric (<18 y.o.) patients. The most common causes of hydrocephalus were as follows: 44 (43.1%) NPH, 35 (34.3%) adult secondary (tumors, subarachnoid
hemorrhage,
et
cetera)
hydrocephalus,
15
(14.7%)
pediatric
primary
(congenital/malformations, aqueduct stenosis, Chiari Malformation, et cetera) and 8 (7.8%) pediatric secondary (tumors, infections, et cetera) hydrocephalus. 11/102 (10.8%) VPS patients had already been revised at least once in the past, while 91/102 (89.2%) patients presented signs and symptoms of VPS malfunction for the first time and therefore were never revised before. The population study demographic data are summarized in Table 1. Overall, 59/102 (57.8%) patients were diagnosed with VPS malfunction and required partial or total shunt revision. Ventricular catheter obstruction/damage/displacement occurred in 12/59 (20.3%) cases,
valve
damage/malfunction
in
11/59
(18.6%)
cases
and
distal
catheter
obstruction/damage/displacement in 17/59 (28.8%) cases; in all these cases a selective (i.e. only at the level of failure) VPS revision was performed. A two levels (valve and proximal catheter or valve and distal catheter) obstruction/damage/displacement was diagnosed in 16/59 (27.1%) cases with subsequent revision at the level of failure; specifically, there were 10 valve plus distal catheter malfunctions and 6 valve plus proximal catheter malfunctions. In 3 (5.1%) cases, despite a mechanically normal VPS function, subclinical infection was detected (Escherichia coli 2 cases, 6
Staphylococcus epidermidis 1 case) and, after proper treatment, subsequent complete VPS revision was performed; we therefore considered these cases among the shunt failure as well. Finally, in 43/102 (42.2%) patients, the VPS function test did not reveal any shunt failure; 38/43 (88.4%) were successfully managed conservatively (e.g. pressure valve adjustments), while in 5 (11.6%) cases a surgical exploration of the shunt was performed anyway due to clinical worsening despite changes in valve opening pressure (2 cases), or unequivocal test results, such as mild resistance to contrastmedium injection or CSF aspiration (3 cases). In all these cases, the surgeon eventually decided to perform a whole system revision with subsequent clinical improvement. The complication rate of the VPS function test in the 102 patients was null; specifically, neither valve damages nor infections occurred. Of the 64 surgically revised patients (62.7%), 6 (9.4%, four pediatric and 2 adult patients) required further VPS revisions. The mean follow-up time was 3.18 years (range 1-7.28), with a minimum of 1-year follow-up (last test performed in November 2018). Test sensitivity and specificity was 92.2% and 100%, respectively, whereas positive and negative predictive value was 100% and 88.4% (Table 2). Outcome data of the VPS function test are summarized in Table 3.
Discussion: CSF shunting was designed more than fifty years ago to address an apparently simple problem, that is hydrocephalus, by transferring an excess of CSF from the brain to another body district capable of reabsorbing it. In the last decades the preferred site for CSF reabsorption has been the peritoneum making VPS with adjustable valves the most frequent shunt used worldwide for both pediatric and adult hydrocephalus.4,21 Since the placement of the first modern shunting systems in 1960, shunts and valves designs have been ameliorated in order to mimic physiologic conditions as closely as possible22 and, nowadays, VPS broadly consist of a proximal (ventricular, either frontal or occipital) catheter, a pressuresensitive valve (either adjustable or fixed pressure) with a reservoir and a distal (peritoneal) catheter.21 Unfortunately, we still know very little about the pathophysiology of hydrocephalus and the current treatment strategies are definitely not curative. Recently, osmotic gradients have been postulated to detain a role in the development of hydrocephalus23 and drainage of CSF through the glymphatic pathways and paravascular spaces has been documented.24,25 These aspects should be considered when evaluating the adequacy of shunt function, even though at the present state of knowledge, the treatment strategy is unlikely to be drastically modified. Still, CSF proteins should be dosed when 7
tapping the shunt for a suspected malfunction and if increased levels are detected, a valve change can be considered. VPS is generally considered a rather simple procedure with a low perioperative risk profile and it is usually performed by young neurosurgeons or residents. Nevertheless, the overall, and especially late (i.e. more than 1 month after surgery), complication rate varies between 25% and 60%, with malfunction and infection being the most common causes of shunt failure.6,7,14,26,27 In this paper a practical, rapid and safe algorithm to test VPS function is presented. This protocol is the result of a long institutional experience in the treatment of hydrocephalus and consequently in CSF shunt malfunction management.20 Furthermore, the proposed method has the advantage of being able to identify the exact point of VPS malfunction/obstruction/failure (proximal catheter, valve device or distal catheter), thus allowing to perform, in most of cases, a selective system revision, reducing the invasiveness and the complication rate of a redo procedure. In fact, of 102 patients (both pediatric and adult) who presented with sign and symptoms of VPS malfunction, all 59 cases with a confirmed intraoperative system malfunction had been correctly diagnosed by applying this algorithm; overall, proximal, valve system and distal catheter failures were diagnosed in 18, 27 and 27 cases respectively, plus 3 subclinical hardware infections. Over the years, several methods have been proposed to diagnose CSF shunt malfunction; they can be divided into two broad categories: imaging studies and so-called invasive shunt tests. Concerning the former, Lehnert et al12 and Griffey et al28 demonstrated that plain radiographic shunt series can only detect catheters discontinuity or dislocation and they are of low diagnostic utility. Brain CT scan is surely the most used exam and, in case of suspected VPS malfunction, is indicated by many as the first exam to be performed21,29: when the ventricles size is greatly enlarged or decreased, CT provides critical diagnostic information. However, neuroimaging does not systematically correlate with clinical outcome: ventricles size may be normal even in the presence of shunt malfunction8,30,31 and on the other hand, dilated ventricles can be also seen in clinically improved patients after VPS.32 Moreover, slight ventricles size changes are difficult to detect, especially because, most of the times, they are measured arbitrarily.33 For this reason, Sze and colleagues19 proposed a reliable method to accurately diagnose even slight ventricular volumes changes on CT scan. Park et al21 addressed the issue of ionizing radiation exposure, especially concerning the pediatric population, by designing a dedicated rapid 4-slices CT scan protocol. Magnetic Resonance (MR) with or without special sequences, like phase contrast (PC) MR, has been employed in this field too.8,34,35 PC-MR is, in fact, able to measure the velocity, the flow and the direction of CSF within the shunt catheters.
8
Therefore, in the suspect of VPS malfunction, CT (preferably) or MR must be performed, but most of the times they are only able to confirm that the system is not working properly, while they cannot diagnose the exact point of system failure. Furthermore, MR is not available in every emergency department, requires patient’s cooperation and it is more time consuming compared to CT scan. Nuclear medicine, and specifically radionuclide technique, is another option to verify shunt system patency.36–39 As reported by Chiewvit et al17 this method has the advantage of being able to identify the point of VPS obstruction, but it implies a shunt tap; moreover, it should be considered that nuclear medicine is not available in every center, especially not in an emergency department scenario. Furthermore, the costs of such exams and the patient’s discomfort, as many authors suggest, with multiple imaging studies at different times after the injection of the radionuclide in the valve reservoir and the suggested patient isolation for several hours after the procedure17,36–38 certainly cannot be overlooked. Many other techniques have also been proposed like for examples, the use of specific otologic tests.16 But, once again, these tests are not able to locate where the system is malfunctioning; as Sakka et al16 correctly pointed out, they may be helpful in an outpatient or even general practitioner situation in order to refer the patient to the hospital when needed, thus contributing to shunt malfunction diagnosis, but they cannot be used as the primary and only method for this aim. The other option is to puncture the VPS reservoir and to seek for the exact point of malfunction with or without the aid of x-rays series15,20; the main disadvantages of these techniques are their (relative) invasiveness and their risk of infection/damage to the hardware. Moreover, most of these methods require the patient being exposed to ionizing radiation. For this reason, some authors proposed less invasive techniques, such as to measure glucose concentration in the CSF obtained from the reservoir40; however, this procedure, despite representing a valid option to diagnose VPS malfunction, also fails to detect the exact point of failure, which in our opinion, instead, should be a key component of a good function test. Therefore, the conclusions made by Savoiardo and colleagues20 more than forty years ago still seem valid and embraceable: the VPS function test with the reservoir tap and the x-ray images as described above is able “to demonstrate rapidly, easily and safely the exact level of malfunction of the shunting system; so, this procedure indicates to the neurosurgeon the exact point where he has to operate”. The study presents some limitations: first of all, it is a retrospective analysis with all its inherent limitations. However, it should also be considered that it would not be ethical to plan a randomized trial with a control group, since hydrocephalus and its manifestations may have life-threatening consequences. 9
Secondly, the proposed method is applicable to in line valves with a reservoir, which are the most commonly implanted; if the valve is not in line and the reservoir lays on the burr hole, only the proximal catheter can be tested, while if there is no reservoir the protocol cannot be applied. Furthermore there is a theoretical risk of infection and/or damage of the VPS15; in the present series neither occurred. It is strongly recommended that the shunt tapping is performed by an experienced neurosurgeon and in a sterile manner. Finally, it is obvious that this diagnostic protocol exposes the patient to ionizing radiations21; however, it should always be considered that VPS malfunction can cause severe neurological deficit and its prompt and exact diagnosis is sometimes a life-saving issue, therefore, x-rays exposition is considered appropriate according to ALARA principles. However, during our VPS function test, we tried to reduce patients’ exposition to radiations as much as possible by complying with a standardized
protocol
(described
above)
conducted
by
an
experienced
neurosurgeon-
neuroradiologist team.
Conclusions: When a VPS malfunction is suspected, its rapid recognition is recommended. The proposed algorithm is a practical, simple and minimally invasive method to accurately diagnose shunt failure. Furthermore, it is able to identify the exact level of malfunction (ventricular catheter, valve device, distal catheter) thus allowing to tailor surgical VPS revision and avoid unnecessary complete system replacement.
10
FIGURE CAPTIONS: Figure 1. (A) Axial brain CT scans of patients with suspected VPS malfunction: a ventricular catheter dislocation/malposition is shown (left), alongside a case of hyper-drainage with slit ventricles and a small subdural collection (red arrow, middle) and a case of hyper-drainage without slit ventricles, but a huge subdural collection with signs of recent hemorrhage (red arrow, right). (B) Plain radiographs showing disconnection of the distal catheter from the valve (red arrow, right) and its migration into the abdomen (red arrows, left).
Figure 2. (A) Sterile nurse table with the material needed for the test: saline solution, iodate contrast medium, 10 ml syringe and needle. (B) While the distal catheter is manually closed (arrow), the saline-iodate contrast solution (see manuscript) is injected to test the ventricular catheter and (C) the contrast flowing into the ventricle is observed on the screen. (D) While the ventricular catheter is manually closed (arrow), the saline-iodate contrast solution (see manuscript) is injected to test the distal catheter and (E) the contrast flowing into the abdomen is observed on the screen. (F) Contrast leakage indicating catheter damage at the cervical level.
Figure 3. VPS function test algorithm (detailed description in the manuscript).
11
TABLE CAPTIONS: Table 1. Patients demographics
Table 2. Contingency table of shunt function test
Table 3. VPS function test outcome
Acknowledgments: The authors wish to dedicate this article to Dr. Ida M. Milanesi, whose commitment to patients and neuroscience was a great source of inspiration for us all.
12
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30.
Engel M, Carmel PW, Chutorian AM. Increased intraventricular pressure without ventriculomegaly in children with shunts: "normal volume" hydrocephalus. Neurosurgery. 1979;5(5):549-552. doi:10.1227/00006123-197911000-00001
31.
Sivaganesan A, Krishnamurthy R, Sahni D, Viswanathan C. Neuroimaging of ventriculoperitoneal shunt complications in children. Pediatr Radiol. 2012;42(9):1029-1046. doi:10.1007/s00247-012-2410-6
32.
Meier U, Paris S, Gräwe A, Stockheim D, Hajdukova A, Mutze S. Is there a correlation between operative results and change in ventricular volume after shunt placement? A study of 60 cases of idiopathic normal-pressure hydrocephalus. Neuroradiology. 2003;45(6):377380. doi:10.1007/s00234-003-0989-x
33.
Iskandar BJ, Tubbs S, Mapstone TB, Grabb PA, Bartolucci AA, Oakes WJ. Death in Shunted Hydrocephalic Children in the 1990s. Pediatr Neurosurg. 1998;28(4):173-176. doi:10.1159/000028644
34.
Drake JM, Martin AJ, Henkleman RM. Determination of cerebrospinal fluid shunt obstruction with magnetic resonance phase imaging. J Neurosurg. 1991;75(4):535-540. 15
doi:10.3171/jns.1991.75.4.0535 35.
Rüegger CM, Makki MI, Capel C, Gondry-Jouet C, Baledent O. An innovative approach to investigate the dynamics of the cerebrospinal fluid in the prepontine cistern: A feasibility study using spatial saturation-prepared cine PC-MRI. Eur J Radiol open. 2014;1:14-21. doi:10.1016/j.ejro.2014.09.005
36.
French BN, Swanson M. Radionuclide Imaging Shuntography for the Evaluation of Shunt Patency. In: Vol 8. Karger Publishers; 1982:39-42. doi:10.1159/000400144
37.
Graham P, Howman-Giles R, Johnston I, Besser M. Evaluation of CSF shunt patency by means of technetium-99m DTPA. J Neurosurg. 1982;57(2):262-266. doi:10.3171/jns.1982.57.2.0262
38.
Vernet O, Farmer JP, Lambert R, Montes JL. Radionuclide shuntogram: adjunct to manage hydrocephalic patients. J Nucl Med. 1996;37(3):406-410.
39.
Kharkar S, Shuck J, Kapoor S, Batra S, Williams MA, Rigamonti D. RADIONUCLIDE SHUNT PATENCY STUDY FOR EVALUATION OF SUSPECTED VENTRICULOPERITONEAL SHUNT MALFUNCTION IN ADULTS WITH NORMAL PRESSURE HYDROCEPHALUS. Neurosurgery. 2009;64(5):909-918. doi:10.1227/01.NEU.0000343545.93153.EB
40.
Zhang H, Peng J, Hao X, Guo X, Li G. A Simple and Reliable Method for the Diagnosis of Ventriculoperitoneal Shunt Malfunction. World Neurosurg. 2017;103:355-359. doi:10.1016/j.wneu.2017.04.051
Disclosure: All the authors are aware of the content of the paper and do not have any financial or other interests that might be construed as a conflict of interest. This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. 16
Table 1. Patients demographics Variable male female
Value 56 (54.9%) 46 (45.1%)
Age
adult (> 18 yo) pediatrics (< 18 yo)
79 (77.5%) 23 (22.5%)
Type of hydrocephalus
NPH adult secondary pediatric primary pediatric secondary
44 (43.1%) 35 (34.3%) 15 (14.7%) 8 (7.8%)
Revisions
1st time revisions redo revisions
91 (89.2%) 11 (10.8%)
Sex
Table 2. Contingency table of shunt function test Shunt malfunction
No shunt malfunction
Total
Positive test
59
0
59
PPV: 59/59 = 100%
Negative test
5
38
43
NPV: 38/43 = 88.4%
Total
64
38
102
Sn: 59/64 = 92.2%
Sp: 38/38 = 100%
PPV: Positive predictive value NPV: Negative predictive value Sn: Senstivity Sp: Specificity
Table 3. VPS function test outcome
Test result
Positive tests characteristics
Negative tests characteristics
Variable positive negative
Value 59 (57,8%) 43 (42,2%)
ventricular catheter failure
12 (21.4%)
valve failure distal catheter failure two-levels failure subclinical infections
11 (19.6%) 17 (30.3%) 6 (10.2%) 10 (16.9%) 3 (5.1%)
conservative management
38 (88.4%)
surgical exploration/replacement
5 (11.6%)
valve + proximal valve + distal
HIGHLIGHTS: -
Ventriculo-peritoneal shunt (VPS) malfunction can lead to severe consequences.
-
It should be promptly and correctly diagnosed and managed.
-
The proposed algorithm is able to accurately detect VPS malfunction and the exact point of system failure (ventricular/distal catheter and/or valve).
-
VPS revision should be selectively performed at the level of failure.
ABBREVIATION LIST: CSF: cerebro-spinal fluid CT: computed tomography MR: magnetic resonance NPH: normal pressure hydrocephalus PC: phase contrast VPS: ventriculo-peritoneal shunt y.o.: years old
The Authors declare that they do not have any financial or other interests that might be construed as a conflict of interest.
- Morgan Broggi: conceptualization, methodology, investigation, data curation, writing - original draft, writing review & editing, project administration - Costanza M. Zattra: methodology, data curation, writing - original draft, writing review & editing - Marco Schiariti: methodology, investigation - Francesco Acerbi: methodology, investigation, writing review & editing - Giovanni Tringali: methodology, investigation, writing review & editing - Jacopo Falco: methodology, writing - original draft, writing review & editing - Laura G. Valentini: methodology, investigation - Giuseppe Faragò: investigation - Paolo Ferroli: methodology, supervision - Giovanni Broggi: conceptualization, methodology, supervision
S1878-8750(20)30265-5
DOI:
https://doi.org/10.1016/j.wneu.2020.02.003
Reference:
WNEU 14277
To appear in:
World Neurosurgery
Received Date: 9 November 2019 Revised Date:
31 January 2020
Accepted Date: 1 February 2020
Please cite this article as: Broggi M, Zattra CM, Schiariti M, Acerbi F, Tringali G, Falco J, Valentini LG, Faragò G, Ferroli P, Broggi G, Diagnosis of ventriculo-peritoneal shunt malfunction: a practical algorithm World Neurosurgery (2020), doi: https://doi.org/10.1016/j.wneu.2020.02.003. This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2020 Elsevier Inc. All rights reserved.
Diagnosis of ventriculo-peritoneal shunt malfunction: a practical algorithm Morgan Broggi1 M.D., Ph.D., Costanza M. Zattra1 M.D., Marco Schiariti1 M.D., Francesco Acerbi1 M.D., Ph.D., Giovanni Tringali1 M.D., Jacopo Falco1 M.D., Laura G. Valentini1 M.D., Giuseppe Faragò2 M.D., Paolo Ferroli1 M.D., and Giovanni Broggi1 M.D. 1
Department of Neurosurgery, and 2Diagnostic Radiology and Interventional Neuroradiology Unit,
Fondazione IRCCS Istituto Neurologico Carlo Besta, Milano, Italy
Corresponding author: Morgan Broggi, M.D., Ph.D. Department of Neurosurgery Fondazione IRCCS Istituto Neurologico Carlo Besta Via Celoria, 11; 20133, Milano, Italy Tel: +39 02 23942411 Fax: + 39 02 70635017 Email: [email protected]
Keywords: Hydrocephalus; Ventriculo-peritoneal shunt; CSF shunt; Shunt malfunction; Ventriculo-peritoneal shunt revision.
Short Title: VPS malfunction: a diagnostic algorithm.
1
ABSTRACT: Objective: This study aims to present a practical method to accurately diagnose ventriculoperitoneal shunt (VPS) malfunction and to detect the exact level at which the system has failed in order to tailor VPS revision at that level only. Methods: A tertiary-referral, single-center algorithm for diagnosis of VPS malfunction is proposed. Based on clinical symptoms and confirmed ventricular dilatation on computed tomography, the VPS reservoir is punctured: if no cerebrospinal fluid (CSF) is obtained, ventricular catheter replacement is recommended. Conversely, if CSF is obtained, a sample is sent for cultural exam and the macroscopic integrity of the whole system is checked via plain x-rays in the angiographic suite. Then, through the injection of iodate contrast medium into the reservoir and selective exclusion of the proximal and distal catheters, the patency and correct VPS functioning are investigated. Results: 102 (56 males, mean age 41.5, range 1-86) patients underwent VPS function test from 2012 to 2018: 59 (57.8%) cases of VPS malfunction were diagnosed. Ventricular catheter obstruction/damage/displacement occurred in 12/59 (20.3%) cases, valve damage in 11/59 (18.6%) cases, distal catheter obstruction/damage/displacement in 17/59 (28.8%) cases and two-levels (valve/proximal catheter or valve/distal catheter) obstruction/damage/displacement in 16/59 (27.1%) cases. Subclinical infection was diagnosed in 3 patients (5.1%). VPS revision was performed selectively at the level of failure. Conclusions: The proposed algorithm is a practical, simple and minimally-invasive technique to accurately diagnose VPS malfunction, identifying the exact level of system failure and allows to tailor surgical VPS revision, avoiding unnecessary complete system replacement.
2
MANUSCRIPT:
Introduction: Hydrocephalus is defined as a pathologic accumulation of cerebrospinal fluid (CSF) in the brain or, more precisely, an active distension of the ventricular system resulting from inadequate passage of CSF from its point of production to its point of absorption.1 It is a relatively common condition, with an estimated 69,000-related hospital discharges reported annually and a mean prevalence of 85/100,000 in the United States.2,3 An established long-term treatment option for hydrocephalus is CSF shunting. It consists most of the times of a ventriculo-peritoneal shunt (VPS),4 while rarely the distal catheter is placed in the right heart atrium. VPS is one of the most commonly performed neurosurgical procedures with an estimated incidence of approximately 5.5 per 100,000 in the U.S.5 However, despite being considered a low risk procedure and regardless advances in shunts design and management, malfunction rates remain high, with approximately 40% of pediatric shunts and 29% of adult shunts failing in the first year of placement and 45-81% of shunt patients requiring at least one surgical shunt revision in their lifetime.6,7 While in the adult so-called normal pressure hydrocephalus (NPH) most VPS malfunctions concern the distal peritoneal catheter, in children proximal ventricular catheter obstruction/malfunction is more common.2,8 Another valid treatment option for hydrocephalus is represented by endoscopic third ventriculostomy; although it may be applied also to communicating hydrocephalus,9 its best results were achieved in treating obstructive hydrocephalus.10 This procedure is considered to have a very low risk profile11 and, especially, it does not carry the risk of “system malfunction”, since no device is implanted. VPS malfunction, on the other hand, can lead to severe consequences with increased morbidity and mortality12 and for this reason, its diagnosis should be prompt and accurate and should be followed by timely VPS revision.13,14 Nevertheless, despite several techniques have been proposed,8,12,15–19 correct recognition of shunt failure is challenging and no consensus guidelines or recommended approach to diagnostic imaging exist nowadays.17 Moreover, the exact segment of system failure (proximal catheter, valve device or distal catheter) is rather tough to identify and, yet again, no standardized method has been approved. The aim of this study is to propose a quick and practical algorithm to easily diagnose VPS malfunction and identify the exact point of system failure in order to address the surgical intervention on the segment actually requiring revision.
3
Methods: A retrospective tertiary referral center study was conducted from January 1st, 2012 to December 31st, 2018 on all shunt patients admitted for symptoms suspicious for VPS failure and who underwent a VPS function test. Our Institute has been deeply committed to the management of hydrocephalus, both pediatric and adult, for more than forty years and outstanding colleagues published the first version of the algorithm used to disclose shunt malfunction.20 Following on that experience, the procedure was revised and ameliorated several times until the approval of the present version, which has been used over the last 10 years. In 2004 the Institutional Ethical Board formally approved this method. Once a patient with a VPS complains of clinical symptoms that are suggestive of system failure, he/she is admitted to the outpatient hospital service and a dedicated protocol is applied. First things first, a clinical examination is carried out, preferably by a neurologist/neurosurgeon who is familiar with the patient and his/her clinical history so that even the slightest neurological changes between preoperative, early postoperative and present status are easier to detect. This examination should also include a simple valve reservoir palpation to look for its rapid reexpansion in order to rule out ventricular catheter obstruction/malfunction; the presence of some “red flags”, like gait imbalance, disorientation, drowsiness, ocular movement deficits (e.g. Parinaud syndrome), nuchal rigidity, meningism and, in general, any worsening of the previous neurological status, should be noted as well. If there is a strong suspicion of hardware infection (e.g. high fever, bad wound healing, skin CSF leakage, et cetera), besides ordering routine blood tests, a shunt tap is performed and CSF is sent for urgent microbiological examination; in these cases, VPS function test is postponed until the test results are back. Following clinical examination, a brain Computed Tomography (CT) scan without intravenous contrast administration is performed: besides comparing ventricles dimensions to previous scans (i.e. when the VPS was supposed to work properly),19 other complications such hyper-drainage with/without subdural collections, hemorrhages and ventricular catheter dislocation are ruled out (Fig. 1A). It is important to underline that the CT is performed mainly to exclude the latter rather than to look strictly at the ventricles’ dimensions; in other words, apart from significant changes in the ventricles size, this aspect is not considered of high importance in the diagnostic process of VPS malfunction. If the CT does not show increased ventricles size and infection is not suspected, the valve opening pressure is modified (no more than 20-40 mmH2O), the patient is discharged and a
4
follow-up visit is planned within 2-4 weeks: if there is clinical improvement, no other recommendations are suggested. Conversely, if the CT scan does show enlarged ventricles compared to previous scans or if there is no clinical improvement at the follow-up appointment, the valve reservoir is firstly pumped and secondly punctured in a sterile manner. If the reservoir does not re-expand and/or no CSF is obtained from the puncture there is a strong suspicion for proximal catheter obstruction/failure and its surgical replacement is indicated. Intraoperatively, after the new catheter is inserted, it is recommended to test both the correct function of the valve and the distal catheter. The former is assessed just connecting the valve to the new proximal catheter and pumping the reservoir, while the latter is checked by draining, through the peritoneal catheter, 10-20 ml of saline solution under hydrostatic pressure or under slight manual pressure. If otherwise CSF is easily tapped from the reservoir, a sample is sent for dosage of CSF proteins level and microbial exam and the patient is transferred to the angiographic suite. Here, initially the integrity of the whole system is checked via a plain radiograph “shunt series” (Fig. 1B) and then, in a sterile manner, the actual VPS function test is conducted (Fig. 2A). The aim of this test is to selectively examine the performance of each segment of the system: first of all, the proximal catheter is (re)checked. This is done because in case of partial obstruction CSF can sometimes be tapped from the reservoir (see above). While the distal catheter is manually closed few cm distal to the valve, the reservoir is punctured, and 3-4 ml of a solution composed by saline and iodate contrast medium (1:1) are gently injected (Fig. 2B). The patency of the proximal catheter is confirmed on the angiographic screen by a homogenous filling of the ventricle with contrast medium (Fig. 2C). If this does not happen or it is hard to inject the solution, proximal complete or partial obstruction should be suspected. Secondly, the valve and the distal catheter are assessed; the proximal catheter is now closed by applying some pressure just before the valve, as described above, and 5-7 ml of a solution composed by saline and iodate contrast medium (1:1) are gently injected (Fig. 2D). The patency of the distal catheter is confirmed on the angiographic screen by a typical “puff” of contrast medium exiting the catheter in the abdomen (Fig. 2E). If this happens, a whole system re-evaluation is recommended and, in specific situations (e.g. insufficient intraperitoneal CSF absorption in patients with multiple previous abdominal surgeries), entire VPS revision or ventriculo-atrial shunt should be considered. Conversely, if the contrast does not reach the abdomen with evidence of integrity and regular course of the distal catheter, a valve malfunction should be suspected and its surgical selective replacement with intraoperative functional test of the proximal and distal catheters (see above) is recommended. Otherwise, if the
5
contrast stops somewhere along the distal catheter, it is likely that the catheter is obstructed or damaged (sometimes an actual leakage of contrast is shown on the angiographic screen, Fig. 2F). The only absolute contraindication for the function test was known allergy to iodate contrast medium. It should be stressed that the injection of the saline/contrast solution should be made by an experienced neurosurgeon in order to prevent complications such as valve damages or multiple reservoir punctures with increased infection risks. The whole process takes few hours (usually less than 4) and, if diagnosis of shunt malfunction is confirmed, the patient is admitted to the hospital ward to undergo shunt revision, which is usually performed on the very same day. The algorithm is schematized in Figure 3. All patients included in the study gave written consent for demographic, clinical and radiological data review and publication.
Results: One hundred and two patients (56 males, 46 females, mean age 41.5, range 1-86 years old (y.o.)) underwent VPS function test as described above in the last seven years (2012-2018). There were 79 (77.5%) adult (>18 y.o.) and 23 (22.5%) pediatric (<18 y.o.) patients. The most common causes of hydrocephalus were as follows: 44 (43.1%) NPH, 35 (34.3%) adult secondary (tumors, subarachnoid
hemorrhage,
et
cetera)
hydrocephalus,
15
(14.7%)
pediatric
primary
(congenital/malformations, aqueduct stenosis, Chiari Malformation, et cetera) and 8 (7.8%) pediatric secondary (tumors, infections, et cetera) hydrocephalus. 11/102 (10.8%) VPS patients had already been revised at least once in the past, while 91/102 (89.2%) patients presented signs and symptoms of VPS malfunction for the first time and therefore were never revised before. The population study demographic data are summarized in Table 1. Overall, 59/102 (57.8%) patients were diagnosed with VPS malfunction and required partial or total shunt revision. Ventricular catheter obstruction/damage/displacement occurred in 12/59 (20.3%) cases,
valve
damage/malfunction
in
11/59
(18.6%)
cases
and
distal
catheter
obstruction/damage/displacement in 17/59 (28.8%) cases; in all these cases a selective (i.e. only at the level of failure) VPS revision was performed. A two levels (valve and proximal catheter or valve and distal catheter) obstruction/damage/displacement was diagnosed in 16/59 (27.1%) cases with subsequent revision at the level of failure; specifically, there were 10 valve plus distal catheter malfunctions and 6 valve plus proximal catheter malfunctions. In 3 (5.1%) cases, despite a mechanically normal VPS function, subclinical infection was detected (Escherichia coli 2 cases, 6
Staphylococcus epidermidis 1 case) and, after proper treatment, subsequent complete VPS revision was performed; we therefore considered these cases among the shunt failure as well. Finally, in 43/102 (42.2%) patients, the VPS function test did not reveal any shunt failure; 38/43 (88.4%) were successfully managed conservatively (e.g. pressure valve adjustments), while in 5 (11.6%) cases a surgical exploration of the shunt was performed anyway due to clinical worsening despite changes in valve opening pressure (2 cases), or unequivocal test results, such as mild resistance to contrastmedium injection or CSF aspiration (3 cases). In all these cases, the surgeon eventually decided to perform a whole system revision with subsequent clinical improvement. The complication rate of the VPS function test in the 102 patients was null; specifically, neither valve damages nor infections occurred. Of the 64 surgically revised patients (62.7%), 6 (9.4%, four pediatric and 2 adult patients) required further VPS revisions. The mean follow-up time was 3.18 years (range 1-7.28), with a minimum of 1-year follow-up (last test performed in November 2018). Test sensitivity and specificity was 92.2% and 100%, respectively, whereas positive and negative predictive value was 100% and 88.4% (Table 2). Outcome data of the VPS function test are summarized in Table 3.
Discussion: CSF shunting was designed more than fifty years ago to address an apparently simple problem, that is hydrocephalus, by transferring an excess of CSF from the brain to another body district capable of reabsorbing it. In the last decades the preferred site for CSF reabsorption has been the peritoneum making VPS with adjustable valves the most frequent shunt used worldwide for both pediatric and adult hydrocephalus.4,21 Since the placement of the first modern shunting systems in 1960, shunts and valves designs have been ameliorated in order to mimic physiologic conditions as closely as possible22 and, nowadays, VPS broadly consist of a proximal (ventricular, either frontal or occipital) catheter, a pressuresensitive valve (either adjustable or fixed pressure) with a reservoir and a distal (peritoneal) catheter.21 Unfortunately, we still know very little about the pathophysiology of hydrocephalus and the current treatment strategies are definitely not curative. Recently, osmotic gradients have been postulated to detain a role in the development of hydrocephalus23 and drainage of CSF through the glymphatic pathways and paravascular spaces has been documented.24,25 These aspects should be considered when evaluating the adequacy of shunt function, even though at the present state of knowledge, the treatment strategy is unlikely to be drastically modified. Still, CSF proteins should be dosed when 7
tapping the shunt for a suspected malfunction and if increased levels are detected, a valve change can be considered. VPS is generally considered a rather simple procedure with a low perioperative risk profile and it is usually performed by young neurosurgeons or residents. Nevertheless, the overall, and especially late (i.e. more than 1 month after surgery), complication rate varies between 25% and 60%, with malfunction and infection being the most common causes of shunt failure.6,7,14,26,27 In this paper a practical, rapid and safe algorithm to test VPS function is presented. This protocol is the result of a long institutional experience in the treatment of hydrocephalus and consequently in CSF shunt malfunction management.20 Furthermore, the proposed method has the advantage of being able to identify the exact point of VPS malfunction/obstruction/failure (proximal catheter, valve device or distal catheter), thus allowing to perform, in most of cases, a selective system revision, reducing the invasiveness and the complication rate of a redo procedure. In fact, of 102 patients (both pediatric and adult) who presented with sign and symptoms of VPS malfunction, all 59 cases with a confirmed intraoperative system malfunction had been correctly diagnosed by applying this algorithm; overall, proximal, valve system and distal catheter failures were diagnosed in 18, 27 and 27 cases respectively, plus 3 subclinical hardware infections. Over the years, several methods have been proposed to diagnose CSF shunt malfunction; they can be divided into two broad categories: imaging studies and so-called invasive shunt tests. Concerning the former, Lehnert et al12 and Griffey et al28 demonstrated that plain radiographic shunt series can only detect catheters discontinuity or dislocation and they are of low diagnostic utility. Brain CT scan is surely the most used exam and, in case of suspected VPS malfunction, is indicated by many as the first exam to be performed21,29: when the ventricles size is greatly enlarged or decreased, CT provides critical diagnostic information. However, neuroimaging does not systematically correlate with clinical outcome: ventricles size may be normal even in the presence of shunt malfunction8,30,31 and on the other hand, dilated ventricles can be also seen in clinically improved patients after VPS.32 Moreover, slight ventricles size changes are difficult to detect, especially because, most of the times, they are measured arbitrarily.33 For this reason, Sze and colleagues19 proposed a reliable method to accurately diagnose even slight ventricular volumes changes on CT scan. Park et al21 addressed the issue of ionizing radiation exposure, especially concerning the pediatric population, by designing a dedicated rapid 4-slices CT scan protocol. Magnetic Resonance (MR) with or without special sequences, like phase contrast (PC) MR, has been employed in this field too.8,34,35 PC-MR is, in fact, able to measure the velocity, the flow and the direction of CSF within the shunt catheters.
8
Therefore, in the suspect of VPS malfunction, CT (preferably) or MR must be performed, but most of the times they are only able to confirm that the system is not working properly, while they cannot diagnose the exact point of system failure. Furthermore, MR is not available in every emergency department, requires patient’s cooperation and it is more time consuming compared to CT scan. Nuclear medicine, and specifically radionuclide technique, is another option to verify shunt system patency.36–39 As reported by Chiewvit et al17 this method has the advantage of being able to identify the point of VPS obstruction, but it implies a shunt tap; moreover, it should be considered that nuclear medicine is not available in every center, especially not in an emergency department scenario. Furthermore, the costs of such exams and the patient’s discomfort, as many authors suggest, with multiple imaging studies at different times after the injection of the radionuclide in the valve reservoir and the suggested patient isolation for several hours after the procedure17,36–38 certainly cannot be overlooked. Many other techniques have also been proposed like for examples, the use of specific otologic tests.16 But, once again, these tests are not able to locate where the system is malfunctioning; as Sakka et al16 correctly pointed out, they may be helpful in an outpatient or even general practitioner situation in order to refer the patient to the hospital when needed, thus contributing to shunt malfunction diagnosis, but they cannot be used as the primary and only method for this aim. The other option is to puncture the VPS reservoir and to seek for the exact point of malfunction with or without the aid of x-rays series15,20; the main disadvantages of these techniques are their (relative) invasiveness and their risk of infection/damage to the hardware. Moreover, most of these methods require the patient being exposed to ionizing radiation. For this reason, some authors proposed less invasive techniques, such as to measure glucose concentration in the CSF obtained from the reservoir40; however, this procedure, despite representing a valid option to diagnose VPS malfunction, also fails to detect the exact point of failure, which in our opinion, instead, should be a key component of a good function test. Therefore, the conclusions made by Savoiardo and colleagues20 more than forty years ago still seem valid and embraceable: the VPS function test with the reservoir tap and the x-ray images as described above is able “to demonstrate rapidly, easily and safely the exact level of malfunction of the shunting system; so, this procedure indicates to the neurosurgeon the exact point where he has to operate”. The study presents some limitations: first of all, it is a retrospective analysis with all its inherent limitations. However, it should also be considered that it would not be ethical to plan a randomized trial with a control group, since hydrocephalus and its manifestations may have life-threatening consequences. 9
Secondly, the proposed method is applicable to in line valves with a reservoir, which are the most commonly implanted; if the valve is not in line and the reservoir lays on the burr hole, only the proximal catheter can be tested, while if there is no reservoir the protocol cannot be applied. Furthermore there is a theoretical risk of infection and/or damage of the VPS15; in the present series neither occurred. It is strongly recommended that the shunt tapping is performed by an experienced neurosurgeon and in a sterile manner. Finally, it is obvious that this diagnostic protocol exposes the patient to ionizing radiations21; however, it should always be considered that VPS malfunction can cause severe neurological deficit and its prompt and exact diagnosis is sometimes a life-saving issue, therefore, x-rays exposition is considered appropriate according to ALARA principles. However, during our VPS function test, we tried to reduce patients’ exposition to radiations as much as possible by complying with a standardized
protocol
(described
above)
conducted
by
an
experienced
neurosurgeon-
neuroradiologist team.
Conclusions: When a VPS malfunction is suspected, its rapid recognition is recommended. The proposed algorithm is a practical, simple and minimally invasive method to accurately diagnose shunt failure. Furthermore, it is able to identify the exact level of malfunction (ventricular catheter, valve device, distal catheter) thus allowing to tailor surgical VPS revision and avoid unnecessary complete system replacement.
10
FIGURE CAPTIONS: Figure 1. (A) Axial brain CT scans of patients with suspected VPS malfunction: a ventricular catheter dislocation/malposition is shown (left), alongside a case of hyper-drainage with slit ventricles and a small subdural collection (red arrow, middle) and a case of hyper-drainage without slit ventricles, but a huge subdural collection with signs of recent hemorrhage (red arrow, right). (B) Plain radiographs showing disconnection of the distal catheter from the valve (red arrow, right) and its migration into the abdomen (red arrows, left).
Figure 2. (A) Sterile nurse table with the material needed for the test: saline solution, iodate contrast medium, 10 ml syringe and needle. (B) While the distal catheter is manually closed (arrow), the saline-iodate contrast solution (see manuscript) is injected to test the ventricular catheter and (C) the contrast flowing into the ventricle is observed on the screen. (D) While the ventricular catheter is manually closed (arrow), the saline-iodate contrast solution (see manuscript) is injected to test the distal catheter and (E) the contrast flowing into the abdomen is observed on the screen. (F) Contrast leakage indicating catheter damage at the cervical level.
Figure 3. VPS function test algorithm (detailed description in the manuscript).
11
TABLE CAPTIONS: Table 1. Patients demographics
Table 2. Contingency table of shunt function test
Table 3. VPS function test outcome
Acknowledgments: The authors wish to dedicate this article to Dr. Ida M. Milanesi, whose commitment to patients and neuroscience was a great source of inspiration for us all.
12
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Disclosure: All the authors are aware of the content of the paper and do not have any financial or other interests that might be construed as a conflict of interest. This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. 16
Table 1. Patients demographics Variable male female
Value 56 (54.9%) 46 (45.1%)
Age
adult (> 18 yo) pediatrics (< 18 yo)
79 (77.5%) 23 (22.5%)
Type of hydrocephalus
NPH adult secondary pediatric primary pediatric secondary
44 (43.1%) 35 (34.3%) 15 (14.7%) 8 (7.8%)
Revisions
1st time revisions redo revisions
91 (89.2%) 11 (10.8%)
Sex
Table 2. Contingency table of shunt function test Shunt malfunction
No shunt malfunction
Total
Positive test
59
0
59
PPV: 59/59 = 100%
Negative test
5
38
43
NPV: 38/43 = 88.4%
Total
64
38
102
Sn: 59/64 = 92.2%
Sp: 38/38 = 100%
PPV: Positive predictive value NPV: Negative predictive value Sn: Senstivity Sp: Specificity
Table 3. VPS function test outcome
Test result
Positive tests characteristics
Negative tests characteristics
Variable positive negative
Value 59 (57,8%) 43 (42,2%)
ventricular catheter failure
12 (21.4%)
valve failure distal catheter failure two-levels failure subclinical infections
11 (19.6%) 17 (30.3%) 6 (10.2%) 10 (16.9%) 3 (5.1%)
conservative management
38 (88.4%)
surgical exploration/replacement
5 (11.6%)
valve + proximal valve + distal
HIGHLIGHTS: -
Ventriculo-peritoneal shunt (VPS) malfunction can lead to severe consequences.
-
It should be promptly and correctly diagnosed and managed.
-
The proposed algorithm is able to accurately detect VPS malfunction and the exact point of system failure (ventricular/distal catheter and/or valve).
-
VPS revision should be selectively performed at the level of failure.
ABBREVIATION LIST: CSF: cerebro-spinal fluid CT: computed tomography MR: magnetic resonance NPH: normal pressure hydrocephalus PC: phase contrast VPS: ventriculo-peritoneal shunt y.o.: years old
The Authors declare that they do not have any financial or other interests that might be construed as a conflict of interest.
- Morgan Broggi: conceptualization, methodology, investigation, data curation, writing - original draft, writing review & editing, project administration - Costanza M. Zattra: methodology, data curation, writing - original draft, writing review & editing - Marco Schiariti: methodology, investigation - Francesco Acerbi: methodology, investigation, writing review & editing - Giovanni Tringali: methodology, investigation, writing review & editing - Jacopo Falco: methodology, writing - original draft, writing review & editing - Laura G. Valentini: methodology, investigation - Giuseppe Faragò: investigation - Paolo Ferroli: methodology, supervision - Giovanni Broggi: conceptualization, methodology, supervision