Literature Review

Cranioplasty Infection and Resorption Are Associated with the Presence of a

Ventriculoperitoneal Shunt: A Systematic Review and Meta-Analysis

Christian M. Mustroph, James G. Malcolm, Rima S. Rindler, Jason K. Chu, Jonathan A. Grossberg, Gustavo Pradilla,Faiz U. Ahmad

-BACKGROUND: Following decompressive craniectomy, hydrocephalus is acommon complication often necessitating placement of a ventriculoperitonealshunt (VPS). Complications in the presence of a VPS have been reported, but aclear association has not been established.

-METHODS: PRISMA guidelines were used to perform a literature searchusing PubMed to identify articles that published the complication rates asso-ciated with staged or simultaneous cranioplasty and VPS placement. From theseevent rates, odds ratios (ORs) with 95% confidence intervals (CIs) of compli-cations were calculated. Data were pooled using the ManteleHaenszel method.The Oxford Center for Evidence-Based Medicine guidelines were used to assessthe quality of individual articles and studies. The NewcastleeOttawa Scale wasused to assess the risk of bias in studies.

-RESULTS: Of the 30 papers reviewed for complications in the presence andabsence of a VPS, 7 studies, with a total of 1635 patients, were eligible for meta-analysis. Overall rates of complications (n [ 1635; OR, 9.75; 95% CI, 4.8e20.1),infection (OR, 4.9; 95% CI, 2.2e10.7), and bone resorption (OR, 10.6; 95% CI,4.9e23.0) were increased when a VPS was placed at the time of cranioplasty.Simultaneous procedures were associated with increased complication rates(n [ 283; OR, 4.3; 95% CI, 2.3e8.2) compared with staged procedures.

-CONCLUSIONS: Cranioplasty in the presence of a VPS is associated with ahigher rate of overall complications, including infection and bone resorption.Performing cranioplasty and VPS placement in the same operation is associatedwith an increased rate of complications compared with staged procedures.Surgeons should consider staging these procedures when possible and counselpatients about these risks.

Key words- Craniectomy- Cranioplasty- Infection- Resorption- Ventriculoperitoneal shunt

Abbreviations and AcronymsCI: confidence intervalCSF: cerebrospinal fluidOR: odds ratioVPS: ventriculoperitoneal shunt

Department of Neurological Surgery, Emory University,Atlanta, Georgia, USA

To whom correspondence should be addressed:Faiz U. Ahmad, M.D., M.Ch.[E-mail: faiz.ahmad@emory.edu]

C.M.M. and J.G.M. are coefirst authors.

Citation: World Neurosurg. (2017) 103:686-693.http://dx.doi.org/10.1016/j.wneu.2017.04.066

Journal homepage: www.WORLDNEUROSURGERY.org

Available online: www.sciencedirect.com

1878-8750/$ - see front matter ª 2017 Elsevier Inc. All

INTRODUCTION

Decompressive craniectomy decreaseselevated intracranial pressure caused bytraumatic brain injury,1,2 ischemic orhemorrhagic stroke,3-5 aneurysmal sub-arachnoid hemorrhage,6 and various otherconditions. Following decompressivecraniectomy, hydrocephalus is a knowncomplication that in some casesnecessitates placement of aventriculoperitoneal shunt (VPS).7,8

Cranioplasty is performed afterdecompressive craniectomy to improvecraniofacial cosmesis, provide cerebralprotection, and potentially improveintracranial hemodynamics andphysiological function.9,10 Cranioplastyoutcomes have been studied with regardto the timing of craniectomy,11,12 type ofmaterial,13,14 and indications for initialcraniectomy,15 and the perioperative risksand complications of cranioplasty,including infection and bone resorption,have been well documented.14,16,17

rights reserved.

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Reported rates of infection and boneresorption range from 4.5% to 18.4%18,19

and from 2% to 5.9%,20,21 respectively. Alimited number of studies have examinedthe rates of complications in the contextof VPS and have yielded varying results.No clear association between the 2procedures has been identified inprevious retrospective studies.Owing to the large variance in reported

outcomes, the purpose of this study was todetermine the rates of complications,bone resorption, and infection in thepresence and absence of a VPS at the timeof cranioplasty via a systematic review andmeta-analysis. An increased understand-ing of these complications in the presence

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and absence of a VPS at the time of cra-nioplasty may improve outcomes andbetter identify risks and the necessary in-terventions in selected patients.

METHODS

Search StrategyFollowing PRISMA guidelines, we per-formed a systematic literature search us-ing PubMed. Articles reportingcomplications related to cranioplasty afterdecompressive craniectomy were recordedif they stratified the cranioplasties in theabsence or presence of a VPS. PubMed wassearched using the terms “cranioplasty” as

dx.doi.org/10.1016/j.wneu.2017.04.066

Figure 1. PRISMA flow diagram.

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CHRISTIAN M. MUSTROPH ET AL. ASSOCIATION BETWEEN CRANIOPLASTY COMPLICATIONS AND SHUNT PRESENCE

well as “shunt,” “ventriculoperitoneal,” or“VPS” in all fields. Journal articles indexedin the database before March 2017 wereincluded, and a bibliographic search wasperformed to identify qualifying articlesand relevant medical journals forinclusion.

Study SelectionArticles describing the complicationsrelated to the presence or absence of VPSat time of cranioplasty in adults wereincluded in the analyses. Cohort studiesand case series that compared infection,resorption, and reoperation rates in morethan 20 adults were included. Operativenotes and case reports were excluded. Nometa-analyses or reviews were found.Studies of pediatric populations22-24 andnon-English articles25,26 were excluded,and attempts were made to contact theauthors of 3 articles that reported thepresence or absence of a VPS but did notdifferentiate among complications. Thesearch results were screened indepen-dently by 2 authors (J.G.M. and C.M.M.),and disagreements were resolved byconsensus.

Data ExtractionData on the number of patients, in-dications for decompressive craniectomy,

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anatomic locations of the procedure, andcranioplasty-associated complicationswere compiled from each article. Com-plications were grouped into the followingcategories: total overall complications;infection requiring treatment (with anti-biotics, drainage, or reoperation), boneresorption (by clinical examination orimaging), and reoperation. Cranioplastiesalso were stratified by the timing of VPSplacement as either simultaneous orstaged (before and after).The Oxford Center for Evidence-Based

Medicine guidelines were used to assessthe quality of individual articles andstudies.27 The risk of bias was evaluatedusing the NewcastleeOttawa Scale, a3-category, 9-point scale for assessingcohort selection, comparability, andoutcome.28 A higher score indicateshigher quality.

Data AnalysisData were analyzed using RevMan 5.3.5(The Cochrane Collaboration, London,United Kingdom). If overall complicationswere not reported in a study, then indi-vidual complications were summed. Forarticles reporting event rates, odds ratios(ORs) with 95% confidence intervals (CIs)of infection, resorption, and reoperationwere calculated. Data were pooled via the

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ManteleHaenszel method using a fixed-or random-effects model, depending onthe heterogeneity of data. For articles onlyreporting ORs and 95% CIs (and not eventcounts), these were used to calculatestandard error and incorporated manuallyinto the ManteleHaenszel calculations.The I2 metric was reported to quantifyheterogeneity (0%, no heterogeneity;100%, maximal heterogeneity).29 A P valueof <0.05 was considered statisticallysignificant.

RESULTS

Our literature review results are depictedin a PRISMA flow diagram in Figure 1.Ninety-seven nonduplicate articles werescreened, including 94 articles from thedatabase search and 3 articles frombibliographic searches.30,31 Twenty articleswere excluded after a full-text review forreasons including lack of data on thepresence and absence of VPS data,2,16,32-36

insufficient data (i.e., authors unreachableor unable to provide),37 and nonreportingof cranioplasty complications.Seven studies, with a total of 1635 pa-

tients and 180 shunts, met our inclusioncriteria (Table 1).30-32,38-41 All 7 studies hadan Oxford Center for Evidence-BasedMedicine level 4 as nonmatched cohortstudies. Indications for initial craniectomyincluded traumatic brain injury, sub-arachnoid hemorrhage, intracerebralhemorrhage, intraventricular hemorrhage,ischemic stroke, ruptured aneurysm,extra-axial hematoma, infection, asepticbone necrosis, cerebrovascular disease,cerebral infarction, arteriovenous malfor-mation, and tumor. Cranial procedure lo-cations, when specified, includedunilateral, bilateral, frontotemporal, tem-poral, frontal, and occipital. To furtherinvestigate staged versus simultaneousVPS and cranioplasty, we included 3additional studies from the PRISMAsearch that did not meet our inclusioncriteria because they provided only eventcounts of complications for simultaneousand staged procedures. In addition, 2studies that met the PRISMA searchcriteria and provided complication ratesfor simultaneous versus staged procedureswere included in this analysis(Table 2).2,32,34,36,42

Study quality ranged from 6 to 7 out of apossible 9 on the NewcastleeOttawa

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Table 1. Characteristics of Included Studies Reporting Complications Related to Cranioplasty in the Presence or Absence of VPS

ReferenceIndication for Decompressive

Craniotomy Location

Number ofPatients

ComplicationsVPS None

Mracek et al., 201538 Stroke, TBI, SAH, ICH Unilateral 22 127 Complication, postoperative lengthof stay, removal

Piedra et al., 201430 TBI 18 157 Complication, hematoma, hydrocephalus,infection, resorption

Schuss et al., 201331 ICH, ischemic stroke, ruptured aneurysm,TBI, other

Bifrontal, unilateral 61 254 Abscess, CSF, fistula, EDH/SDH,hygroma, wound healing disturbance

Schwarz et al., 201639 SAH, ischemic stroke, tumor, ICH,extra-axial hematoma, infection, asepticbone necrosis, other

Bilateral, unilateral 21 482 Bone flap necrosis

Tsang et al., 201540 Cerebrovascular disease, infection,TBI, tumor

21 141 Flap depression, infection

Yang et al., 201332 ICH, ischemic stroke, SAH, TBI, tumor 21 109 Infection, resorption

Zhang et al., 201741 TBI, SAH, ICH, tumor, arteriovenousmalformation

Frontotemporal, temporal,frontal, occipital

16 185 Resorption

Totals 180 1455

1635

VPS, ventriculoperitoneal shunt; TBI, traumatic brain injury; SAH, subarachnoid hemorrhage; ICH, intracerebral hemorrhage; CSF, cerebrospinal fluid; EDH, epidural hemorrhage; SDH, subduralhemorrhage.

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CHRISTIAN M. MUSTROPH ET AL. ASSOCIATION BETWEEN CRANIOPLASTY COMPLICATIONS AND SHUNT PRESENCE

Scale. None of the studies includedmatched cohorts, which significantly in-creases the risk of selection bias. Allstudies had adequate follow-up time, withlow patient loss.

Overall ComplicationsAll 7 studies reported complications in thepresence and absence of a VPS(Table 3).30-32,38-41 The pooled rate ofoverall complications in these studiesreporting event rates was 7.0% (52 of746), with rates for individual studiesranging from 3.2% to 11.1%.30,37 Theoverall rate of complications wassignificantly higher in the presence of aVPS compared with the absence of a VPS(18.5% [22 of 119] vs. 5.1% [30 of 589];OR, 9.75; 95% CI, 4.8e20.1; P < 0.01)using a random-effects model (I2 ¼ 87%;P < 0.01).

InfectionThree studies reported infectious compli-cations that necessitated antibiotic treat-ment with or without reoperation forabscess drainage or implant removal(Table 4).30,31,38 The studies used a wide

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range of definitions of infection,including osteomyelitis of the bone flapand surgical site infections, asdemonstrated by fever, erythema,drainage, or cellulitis30,32,40; elevatedwhite blood cell count or evidence ofinfection on computed tomographyscan30; epidural and subduralempyema32; and others.32 Three studiesdid not report the rate of infection in thepresence and absence of a VPS.31,38,39

The pooled rate of infection for thosereporting event rates was 9.0% (25 of 292),with rates for individual studies rangingfrom 8.0% to 9.2%.30,31 The presence of aVPS at cranioplasty was associated with asignificantly increased rate of infectioncompared with the absence of a VPS(26.2% [11 of 42] vs. 5.6% [14 of 250]; OR,4.9; 95% CI, 2.2e10.7; P < 0.01) using arandom-effects model (I2 ¼ 89%; P <0.001).

Bone ResorptionSix studies reported bone graft resorption,as determined by clinical examination orimaging (Table 5).30,31,38-41 The pooled rateof bone resorption for those reporting

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events rates was 3.98% (27 of 678), withrates for individual studies ranging from3.09% to 5.9%.30,37 The presence of aVPS at the time of cranioplasty wasassociated with a significantly increasedrate of resorption necessitatingreoperation compared with the absenceof a VPS (11.2% [11 of 98] vs. 2.76% [16of 580]; OR, 10.6; 95% CI, 4.86e22.97;P < 0.01) using a random-effects model(I2 ¼ 62%; P < 0.01).

Simultaneous and Staged VPSFive studies reported complications thatcould be stratified into simultaneous orstaged VPS (Figure 2). Complicationsincluded infections, resorption,reoperation, intracerebral hemorrhage,epidural hemorrhage, subduralhemorrhage, and hydrocephalus. Thepooled rate of all complications insimultaneous and staged VPS was 23.0%(65 of 283), with rates in individualstudies ranging from 9.2% to 45.8%.2,38

Simultaneous VPS and cranioplasty wasassociated with a higher rate ofcomplications compared with stagedsurgeries (45.7% [43 of 94] vs. 11.6%

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Table 2. Characteristics of Included Studies Reporting Complications Related to Cranioplasty with Staged or Simultaneous VPS

ReferenceIndication for Decompressive

Craniotomy Location

Number of Patients

ComplicationsSimultaneous Staged

Heo et al., 201434 Trauma, SAH, ICH, cerebral infarction,brain tumor, IVH

32 19 Subdural fluid collection, SDH, infection,ICH, EDH

Jung et al., 20152 TBI, aneurysm, ICH, infarction Unilateral, bilateral 14 10 Infection, SDH, resorption, shunt malfunction

Schuss et al., 201542 TBI, SAH, ICH Unilateral 17 24 Bleeding, infection/wound healingdisturbance, hygroma, other

Von der Brelie et al., 201536 TBI, ischemic stroke, hemorrhagic stroke 27 10 Aseptic necrosis, empyema, explantation ofbone flap

Yang et al., 201332 21 109 Infection, resorption

Totals 111 172

283

SAH, subarachnoid hemorrhage; ICH, intracerebral hemorrhage; IVH, intraventricular hemorrhage; SDH, subdural hemorrhage; EDH, epidural hemorrhage; TBI, traumatic brain injury.

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[22 of 189]; OR, 4.31; 95% CI, 2.25e8.23;P < 0.0001) using a fixed-effects model(I2 ¼ 0%; P ¼ 0.65).

DISCUSSION

In this systematic review of reports on thecomplications associated with the pres-ence and absence of a VPS at the time ofcranioplasty, we found that VPS placementat the time of cranioplasty is associatedwith a greater overall risk of complicationsand an increased risk of infection andbone resorption. In addition, staging ofthe VPS and cranioplasty procedures was

Table 3. Event Rates and Odds Ratios of Oveand Pooled Results

Reference

Totals

VPS None

Piedra et al., 201430 18 139

Mracek et al., 201538 22 127

Schwarz et al., 201639 21 482

Tsang et al., 201540 21 141

Yang et al., 201332 21 109

Schuss et al., 201331 61 254

Zhang et al., 201741 16 185

Pooled*

VPS, ventriculoperitoneal shunt; OR, odds ratio; CI, confidence*Mantel-Haenszel method using a random-effects model with

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associated with lower complication ratescompared with performing these proced-ures simultaneously. In patients needingcranioplasty and a VPS, it may be prudentto stage these procedures whenever clini-cally possible. Furthermore, in susceptiblepatients, surgeons should consider usingnonresorptive synthetic implants and anextended course of perioperative antibi-otics. The effects of lumbar drains orexternal ventricular drains for the solepurpose of delaying VPS have not beenwell reported in the literature.Given the association between VPS

placement at the time of cranioplasty and

rall Complications for Individual Studies

Complications

OR (95% CI)VPS None

0.68 (0.15e3.01)

35.6 (9.96e127)

1.73 (1.02e2.92)

9 9 11.0 (1.81e74.1)

5 7 4.55 (3.29e5.81)

4 6 2.90 (1.60e4.20)

4 8 7.38 (0.68e1.94)

9.75 (4.79e20.1)

interval.heterogeneity; I

2 ¼ 87%, P < 0.01.

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simultaneous/staged procedures and anincreased risk of complications, it may beinferred that VPS placement after cranio-plasty may be recommended over VPSplacement before cranioplasty. Similarly,Oh et al.33 showed that in large concaveflaccid cranial defects complicated byhydrocephalus, neurologic outcomes (asmeasured by the Glasgow OutcomeScale), dysphagia, and visual acuitytended toward improvement in patientsundergoing VPS placement aftercranioplasty compared with thoseundergoing VPS placement beforecranioplasty. In addition, compared witha combined group of patients with VPSplacement before and duringcranioplasty, patients with staged VPSplacement after cranioplasty had a lowerrate of complications as measured bysubdural hygroma, subdural hematoma,epidural fluid collection, andreoperation.35 It may be that until thecranioplasty is in place, the cerebrospinalfluid (CSF) dynamics are in flux, possiblyresulting in further shunt revisions andother complications.

Comparison with Previous ReviewsNo previous reports have addressed thisquestion, despite the fact that VPS is oftennecessary after decompressive craniec-tomy and before cranioplasty. In a meta-analysis investigating the timing ofcranioplasty and subsequent complica-tions, early cranioplasty (within 90 days)

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Table 4. Event Rates and Odds Ratios of Infections for Individual Studies and PooledResults

Reference

Totals Infections

OR (95% CI)VPS None VPS None

Yang et al., 201332 21 109 5 7 4.55 (1.29e16.10)

Piedra et al., 201430 18 157 1.94 (0.52e7.18)

Tsang et al., 201540 21 141 6 7 7.66 (2.27e25.78)

Pooled* 4.85 (2.21e10.65)

VPS, ventriculoperitoneal shunt; OR, odds ratio; CI, confidence interval.*ManteleHaenszel method using a random-effects model and heterogeneity; I

2 ¼ 89%, P < 0.001.

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CHRISTIAN M. MUSTROPH ET AL. ASSOCIATION BETWEEN CRANIOPLASTY COMPLICATIONS AND SHUNT PRESENCE

was associated with an increased risk ofdeveloping hydrocephalus.12 With this inmind, it is important to investigate theoptimal timing for shunt placement andassociated complications.The present review includes studies

spanning the last decade, highlighting thecontinued interest in minimizing compli-cations associated with routine cranio-plasty. Despite this interest, however, noprospective studies have yet addressed thetopic of complications associated withcranioplasties in relation to VPS placement.

Overall ComplicationsThe overall rate of complications rate in theincluded studies varied widely, from 3.17%to 11.1%.31,37 A recent large systematic re-view reported a 6.4% rate of cranioplastycomplications.43 The difference in overallcomplication rates may be the result of

Table 5. Event Rates and Odds Ratios of ResResults

Reference

Totals

VPS None

Schuss et al., 201331 61 254

Piedra et al., 201430 18 157

Mracek et al., 201538 22 127

Schwarz et al., 201639 21 482

Tsang et al., 201540 21 141

Zhang et al., 201741 16 185

Pooled*

VPS, ventriculoperitoneal shunt; OR, odds ratio; CI, confidence*ManteleHaenszel method using a random-effects model with

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widely varying definitions of complicationsand might be resolved with more clearlydefined complications or a narrower list.The relatively high rate of complicationsrelated to cranioplasty demonstrates theneed to further investigate outcomes andfind improved interventions for thesepatients. We believe that reporting specificcomplication rates instead of overallcomplication rates will be moreinformative in future studies.

InfectionThe pooled infection rate of infection of9.0% identified in our analysis is compa-rable to previously reported combined in-fections rates of 4.5%e18.4.18,19 Theinfection rates in patients undergoingcranioplasty are reportedly affected bylength of hospital stay, interval betweencraniectomy and cranioplasty, presence of

orption for Individual Studies and Pooled

Resorption

OR (95% CI)VPS None

4 6 2.90 (0.79e10.6)

0.68 (0.15e3.01)

35.6 (9.96e127)

1.73 (1.02e2.92)

3 2 11.6 (1.81e74.1)

4 8 7.38 (0.68e1.94)

10.57 (4.86e22.97)

interval.heterogeneity; I

2 ¼ 62%, P < 0.01.

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systemic infection, low hemoglobin, poorneurologic status, additional operations,and stroke.12,15,42

ResorptionThe pooled rate of bone resorption of3.98% is comparable to rates of 3.09% and4.18% reported previously.30,31 Boneresorption rates as high as 16% have beenreported in adult patients, and rates of14%e42% have been reported in pediatricpopulations.43 It may be prudent to furtherinvestigate bone resorption in thepresence of a VPS in this population.Zhang et al.41 postulated that thechanges in fluid mechanics andintracranial pressure associated with aVPS lead to fine motion causingincreased bone resorption at the edges ofa bone flap. The increased rate ofresorption may make the use of artificialbone flaps more favorable in patientsneeding cranioplasty and VPS placement.

Simultaneous and Staged VPSThe pooled rate of all complications was23.3% (66 of 283), with individual ratesranging from 9.2% to 45.8%. This pooledrate was driven primarily by Heo et al.,34

who reported a complication rate of43.2% (22 of 51). Of the 22 complicationsreported by Heo et al., 17 consisted ofinfections and subdural fluid collection, 2of the most common complicationsassociated with cranioplasty. The highrate of subdural fluid collection may beexplained by the difficulty in adjusting theVPS for changing intracranial pressure.Heo et al. postulated that increased ordecreased pressure in the subdural spaceafter cranioplasty alters intracranialpressure, and that this change, combinedwith altered cerebral vasculature andcerebral perfusion pressure, causesfluctuations in intracranial pressure.Furthermore, the weight of this study inthe meta-analysis (27.4%, calculateddirectly from its standard error) is compa-rable to that of Jung et al.2 (27.2%) andYang et al.32 (20.1%) and, therefore, doesnot appear to significantly skew the results.In light of these studies, we believe that

when a patient requires both operationssimultaneously, especially with a bulgingbrain preoperatively, CSF drainage vialumbar or ventricular puncture should beconsidered to control the intracranialpressure and avoid complications. VPS

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Figure 2. Forest plot of studies reporting complications ofcranioplasty with staged or simultaneous VPS. The blue squaredata markers indicate odds ratio (ORs) from primary studies,with sizes reflecting the statistical weight of the study usingrandom-effects meta-analysis. The horizontal lines indicate 95%

confidence interval (CI). The diamond data markers representthe subtotal and overall OR and 95% CI. The vertical solid lineindicates the line of no effect (OR 1). Results indicate decreasedoverall complications with staged cranioplasty and VPSprocedures.

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placement could be done at a later date todecrease the risk of complications. Inaddition, when planning very early cranio-plasty, patients with a high external ven-tricular drain output (>150 mL/day) mayrequire simultaneous shunt placement.44

The therapeutic benefits of theseprocedures must be weighed against theincreased risks, including infection,neurologic sequelae, and bone resorption.The rate of postdural puncture meningitishas been reported as 1.3/10,000, whereasthe rate of neurologic deterioration afterlumbar puncture in patients with elevatedintracranial pressures has been reportedto be between 12% and 13%.45-47 The risksof these procedures in the setting ofcranioplasty has not yet been examined,and further investigation is needed tobetter clarify the role of these proceduresin helping stage cranioplasty and VPSplacement.The mean interval between initial cra-

niectomy and cranioplasty in the 7 studiesvaried from 46 days to 370 days.38,39 Thetime between VPS and cranioplasty wasnot specified in the 7 studies that weevaluated, and this information may helpelucidate an optimal window between the2 procedures to minimize complications.Cranioplasty performed within 90 days ofVPS placement is associated with anincreased risk of developing hydrocepha-lus, suggesting that an interval of >90days may be preferred for patients sus-ceptible to hydrocephalus.12

Study Strengths and LimitationsThis report is the sole systematic reviewand meta-analysis published to dateexploring the effect of VPS placement at

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the time of cranioplasty on complicationrates. It builds on previous studies thathave addressed the question of complica-tions associated with the presence of aVPS during cranioplasty and the timing ofthe 2 procedures in relation to oneanother. Through communication withthe authors of those studies, we haveadded new data to more completelyaddress this question.Limitations of this study include the

heterogeneity of the study populations,which included multiple indications fordecompressive craniectomy and varyinganatomic locations. Five of the 7 studiesincluded in this analysis incorporated amix of indications.30,37,40,41,48 Althoughthe majority of craniectomies were per-formed for decompressive indications, wewere unable to quantify their proportion inour meta-analysis. Complication type andfrequency have been shown to differ byindication for craniectomy; thus, it may beprudent to further stratify craniectomies interms of their indication to better under-stand the possible influence of VPS.43

The presence of a VPS and its associa-tion with increased complications may beconfounded by patients with a more severepresentation manifesting in increasedcomplications. The patient populations inthe evaluated studies varied in terms ofdemographics, size of craniectomy defect,indications for craniectomy, type of cra-niectomy, and severity of hydrocephalus;however, the total population size andstrength of associations still suggest thatthe presence of the shunt itself may be anissue. We recommend that any random-ized trial control for these variables asmarkers of severity or include these

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variables as covariates in a propensityscore analysis.Three of the 7 studies specified the

location of decompressive craniectomy,either unilateral or bifrontal, whereas theremaining 4 did not.37,40,41 Complicationrates have been shown to differ betweenthese 2 surgical approaches, owing toinherent differences in underlying anat-omy cerebral blood flow, CSF flow dy-namics, and bone flap and surface areasize.45,49 The presence of a VPS shunt mayhelp reduce complications especially incases of CSF flow disruption, and thussubgroup analysis may help further clarifythe effect of VPS placement depending onthe type of cranioplasty.Definitions of complications varied

widely among the evaluated studies,relying on imaging, laboratory test, andclinical examination findings. Owing tothe heterogenous definitions of compli-cations, the severity of complications,clinical implications, and outcomes aredifficult to assess and cannot be readilystratified based on severity.

CONCLUSION

In this systematic literature review andmeta-analysis, we investigated thecomplication rates associated with cra-nioplasty in the presence and absence of aVPS. Our findings suggest that VPSplacement at the time of cranioplasty isassociated with an increased overall rate ofcomplications, particularly infection andresorption, compared with staged cranio-plasty and VPS placement. Future studiesshould address these findings in specificpatient populations and focus on the

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prevention of resorption and infection inthe setting of simultaneous cranioplastyand VPS placement.

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Conflict of interest statement: The authors declare that thearticle content was composed in the absence of anycommercial or financial relationships that could be construedas a potential conflict of interest.

Received 1 October 2016; accepted 9 April 2017

Citation: World Neurosurg. (2017) 103:686-693.http://dx.doi.org/10.1016/j.wneu.2017.04.066

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