Cerebrospinal fluid diversion prior to posterior fossa tumor resection in adults: A systematic review

Abstract

Background

Posterior fossa tumors (PFTs) comprise 15%–20% of adult brain tumors, with the reported frequency of hydrocephalus (HCP) ranging between 3.7% and 58%. Most HCP resolves after resection of PFTs, but studies report persistent or new-onset HCP occurring in between 2% and 7% of cases. Preoperative cerebrospinal fluid (CSF) diversion with a ventriculoperitoneal shunt (VPS), external ventricular drain (EVD), or endoscopic third ventriculostomy (ETV) has been shown to improve outcomes. Evidence regarding the efficacy of these techniques is limited.

Methods

A systematic literature search was performed in line with Preferred Reporting Items for Systematic Reviews and Meta-Analyses. Data points were extracted from individual patient cohort data. A failure rate was determined by the number of patients requiring further postoperative CSF diversion.

Results

In total, 8863 records were identified. Thirteen studies consisting of 17 patient cohorts met our inclusion criteria. Across all individual cohort studies, 2976 patients underwent surgical resection of a PFT in whom the frequency of hydrocephalus at presentation was 22.98% (1.92%–100%), and persistent hydrocephalus following preoperative CSF diversion was 13.63% (0%–18%). Of the 684 hydrocephalic patients, 83.63% underwent CSF diversion in the form of ETV, EVD, or VPS. Between years 1992 and 2020, 1986 and 2021, and 1981and 2013, the pre-resection ETV, EVD, and VPS failure rates were 14.66% (17/116), 16.26% (60/369), and 0% (0/87), respectively.

Conclusions

This systematic review highlights that VPS has a better failure rate profile in minimizing postoperative hydrocephalus in adult patients with PFTs.

Posterior fossa tumors (PFTs) comprise 15%–20% of adult brain tumors.¹ Tumors arising within the limited volume of the posterior fossa can produce a mass effect with compression of the cerebellum, brainstem, and/or fourth ventricle.² The frequency of hydrocephalus (HCP) in adults with PFTs ranges between 3.7% and 58%.^3–5

Although the majority of HCP resolves after resection of PFTs, studies have reported a rate of persistent and new-onset HCP after PFT surgery of between 2% and 7%,^6–8 with postoperative HCP adversely affecting prognosis, increasing the length of stay and cost of hospitalization.⁹

When PFT resection does not resolve the HCP, postoperative cerebrospinal fluid (CSF) diversion has been implemented to manage postoperative HCP¹⁰ with placement of a ventriculoperitoneal shunt (VPS), an external ventricular drain (EVD), or endoscopic third ventriculostomy (ETV).^6,11 Advantages of preoperative CSF diversion include symptomatic improvement, relaxation of the cerebellum during surgery (thereby minimizing iatrogenic injury), decreased incidence of CSF leak post-PFT resection, a reduction in inpatient mortality, and a reduced requirement for postoperative CSF diversion.^12–15

Determining the best preoperative CSF diversion method is not straightforward. ETV is considered if the obstructive HCP is expected to be reversible following PFT resection, and VPS is selected if the HCP is unlikely to be reversible.¹⁶ Although EVD placement resolves CSF obstruction in most cases, particularly when gross total resection of the PFT is achieved, 1.2%–6.9% of patients will still require permanent CSF diversion post-tumor resection.¹⁷

A selective approach to preoperative CSF diversion is mandated by the risks including neurological injury,^18–20 intracranial infection, hemorrhage, VPS malfunction, and postoperative ETV obstruction.⁹ These risks are justified in patients with acute symptomatic hydrocephalus where re-establishing CSF flow is a priority.

It is helpful to define the population at risk of persistent hydrocephalus²¹ and identify which CSF diversion method is preferable in reducing post-PFT resection complications. Many studies have examined predictive factors for postoperative hydrocephalus,^22–25 particularly in pediatric patients²² with limited studies addressing the adult cohort.^8,25 We, therefore, performed a comprehensive systematic review, to retrospectively analyze CSF diversion treatment modalities utilized in adult patients prior to PFT resection, and determine which method is most successful.

Methods

We performed this systematic review following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines (Figure 1), and the study protocol was published on PROSPERO (CRD42022357254). A systematic search of 6 databases (PubMed, APA PsychInfo, Embase, Medline, Global Health, and Cochrane Reviews) was performed for articles published before September 23, 2022. The following keywords were searched in all databases: “CSF diversion,” “posterior fossa tumour,” “hydrocephalus,” and variations of the intervention names (EVD, ETV, and VPS)—see Supplementary Appendix A for the search strategy.

Figure 1.

PRISMA flow diagram of the study selection process for this review.

Three authors (A.B.M., F.A., and A.I.) independently and blindly screened the titles and abstracts for relevance. All references were further screened, and relevant literature was harvested that was not identified in the initial screen. We sought studies that met the inclusion and exclusion criteria as per our selection criteria defined in our Patient, Intervention, Comparison and Outcomes (PICO) model (Table 1). Any conflicts of inclusion or queries were resolved by consensus discussion and agreement between senior authors (A.B.M., J.P.L., B.V., and J.R.P.).

Table 1.

The Selection Criteria for Screening Based on the Patient, Intervention, Comparison, and Outcomes (PICO) Model

PICO	Inclusion	Exclusion
i. Population or participants and conditions of interest	Aged 16 years or over. Preoperative patients With posterior fossa neoplasm With or without hydrocephalus on preoperative imaging	Below 16 years of age Nonoperative management Brainstem neoplasm
ii. Interventions or exposures	Surgical management of posterior fossa lesion via any of the following 3 modalities: external ventricular drain (EVD), ventriculoperitoneal shunt, or endoscopic ventriculostomy (ETV), placed prior to resection of the posterior fossa tumor only	Hydrocephalus not associated with tumor Previously operated cranial surgery Previous CSF diversion Postoperative CSF drainage as initial CSF diversion treatment
iii. Comparisons or control groups	Adult patients with or without hydrocephalus who have had CSF diversion performed with any of the three modalities listed above	Below 16 years of age Alternative CSF diversion modality used
iv. Outcomes of interest	Requirement of further postoperative CSF diversion	—
v. Setting	Hospital admission to a secondary or tertiary center	—
vi. Study designs	Retrospective cohort studies (observational studies)	Not in English Full text unavailable Not original research Case reports

Data extraction was performed independently by (A.B.M., F.A., A.I., and A.V.). Publication information (author, year published, country of origin); overview of study design (aims, intervention studied, follow-up period); patient characteristics (sex ratio, mean age, presence of pre- or postoperative hydrocephalus); nature of intervention (type of intervention, failure and success rate, conversion rate, surgical outcome); tumor information (size, location and type of tumor, extent of tumor resection). Preoperative hydrocephalus was determined by both clinical and radiological findings. Preoperative clinical hydrocephalus was determined with symptoms including but not limited to headache, nausea, vomiting, and papilledema. Preoperative radiological hydrocephalus was determined with the use of CT with/without MRI imaging assessing the Evan Index >0.3 and compression of the aqueduct of Sylvius. Papers were graded and assessed qualitatively using the Newcastle–Ottawa quality assessment scale for cohort studies as shown in Supplementary Appendix B.

Results

A comprehensive literature search was performed from the inception of each respective database to September 23, 2022, as displayed in Figure 1. Our search returned 8863 records, of which 13 studies consisting of 17 patient cohorts met our inclusion criteria. Across all cohort studies, 2976 patients underwent surgical resection of a PFT, and 684 patients had preoperative hydrocephalus, of whom 83.63% (572/684) underwent pre-/intraoperative CSF diversion in the form of ETV, EVD, or VPS. For all patients included in this study, CSF diversion was required due to preoperative hydrocephalus or to prophylactically reduce the likelihood of postoperative hydrocephalus. Most studies confirmed preoperative hydrocephalus radiologically (12/13 studies), with a portion of these also recording symptomatic diagnoses (9/13).

Endoscopic Third Ventriculostomy

The use of ETV for preoperative CSF diversion in adult PFTs was found in 5 patient cohorts^5,25–29 between the years 1992 and 2020, with a total of 190 surgically managed adult PFT cases as shown in Table 2. An average age of 42.62 years (28–55 years), of which approximately 51.77% (73/141) are female.

Table 2.

Systematic Review: Cerebrospinal Fluid Diversion Using Endoscopic Third Ventriculostomy Outcomes in Adults Prior to Posterior Fossa Tumor Resection

References	Total adult PFT cases (N)	Preoperative HCP cases (N)	CSF diversion cases (N)	Age (years)	Male (female) (N)	Follow-up	Postoperative HCP (N)	CSF drainage failure (N)	Details of failure	Failure rate (%)	Postoperative complications (N)	Anatomical location of tumor	Histopathology of tumor	Extent of tumor resection (N or %)
Ardakani et al. (2014)27	8	8	8	47.5	5 (3)	6 months	3	VPS (2), Death (1)	Meningitis requiring VPS (1), Fulminate meningitis leading to death (1), HC requiring VPS (1), All 3 within first-week postop	37.50%	0	CPA with mass effect on brainstem (VS)	VS (8)	NS
Grunert et al. (2003)26	49	49	49	35	NS	NS	9	VPS (7)	NS	14.29%	0	“Compressing aqueduct”	NS	NS
Mangubat et al. (2009)29	43	8	8	46.8	NS	NS	4	VPS (4)	0	50%	NS	Posterior fossa (NS)	Unable to determine from data	NS
Marx et al. (2018)5	74	35	35	55	16 (19)	Mean follow-up of 67.2 months (2–204 months)	3	ETV re-do (1), EVD (2)	1 additional wound revision due to CSF fistula	8.57%	CSF collection (conservative) (1), CSF fistula—wound revision (1), re-bleed (1), cerebellar infarct (1), post-resection edema with herniation (1), ventriculitis (1), EDH (1)	NS	Metastasis (10), meningioma (12), VS (3), hemangioblastoma (1), ependymoma (2), pilocytic astrocytoma (3), dermoid (3), sarcoma (1)	GTR (23), STR (12)
Salah et al. (2022)28	16	16	16	28.31	10 (6)	Median was 9 months (3–13 months)	1	Converted to EVD followed by VPS (1)	18M cerebellar astrocytoma, CSF infection 5D post-tumor resection. EVD and Abx, followed by VPS	6.25%	0	NS	Cerebellar astrocytoma (5), ependymoma (5), medulloblastoma (4), diffuse pontine glioma (2)	NS

Abbreviations: Abx, antibiotics; CPA, cerebellopontine angle; CSF, cerebrospinal fluid; EDH, extradural hemorrhage; ETV, endoscopic third ventriculostomy; EVD, external ventricular drain; GTR, gross total resection; HCP, hydrocephalus; NS, not stated; PFT, posterior fossa tumor; STR, subtotal resection; VPS, ventriculoperitoneal shunt; VS, vestibular schwannoma.

In all, 61.05% (116/190) of adult PFTs presented with preoperative hydrocephalus. One hundred percent were managed initially with a preoperative/intraoperative ETV, of which 17.24% (20/116) were found to have postoperative hydrocephalus on CT or MR imaging, with a resultant preoperative ETV failure rate of 14.66% (17/116). Failed ETVs were managed with VPS insertion in 82.35% (14/17), a right-sided EVD in 11.76% (2/17), and a revision ETV in 5.88% (1/17) of cases.

Marx et al.⁵ reported complications (7 in total) including 2 hemorrhages, 1 CSF collection managed conservatively, 1 CSF fistula managed with wound revision, 1 cerebellar infarct, 1 post-resection edema with herniation, and 1 ventriculitis. Three-fifths of studies^26–28 reported no complications, with 1 study not stating whether or not they had complications.²⁹

External Ventricular Drain

EVDs were used for preoperative CSF diversion in 7 patient cohorts^{5,8,9,30–33} between years 1986 and 2021, with a total of 2168 surgically managed adult PFT cases as shown in Table 3. An average age of 52.84 years (19–83 years),^5,8,9,33 of which approximately 58.53% (957/1635) patients were female. Three patient cohorts did not state the average age and sex of patients,^30–32 yet were included as the age of the youngest included patient was 16 years.

Table 3.

Systematic Review: Cerebrospinal Fluid Diversion Using External Ventricular Drain Outcomes in Adults Prior to Posterior Fossa Tumor

Reference	Total adult PFT cases (N)	Preoperative HCP cases (N)	CSF diversion cases (N)	Age (years)	Male (female) (N)	Follow-up	Postoperative HCP (N)	CSF drainage failure (N)	Details of failure	Failure rate (%)	Postoperative complications (N)	Anatomical location	Histopathology of tumor	Extent of tumor resection (N or %)
Atlas et al. (1996)32	104	3	3	NS	NS	12–48 months	NS	0	0	0%	CVA (1)	CPA	VS	50% GTR
Marx et al. (2018)5	74	2	2	NS	NS	NS	0	0	0	0%	0	NS	NS	NS
Pirouzmand et al. (2001)30	284	39	35	54.31	18 (17)	Mean of 26.4 months (6–120 months)	5	VPS (5)	NS	14.28%	Pseudo-meningocele, CN 6/9/10 palsies	CPA	VS (27), meningioma (5), NF2 (2), hemangioma (1)	NS
Prabhuraj et al. (2017)31	145	75	19	50.42	NS	6 months	Yes, details NS	VPS (4)	NS	21.05%	NS	CPA	VS (19)	NS
Saad et al. (2021)33	617	74	117	51	50 (67)	NS	37	VPS (37)	NS	31.62%	Postop IVH, need for re-op	NS	NS	GTR 62%
Won et al. (2020)8	262	100	186	NS	NS	Mean of 19.2 months	12	VPS (12)	3/12 VPS revision (2 infection, 1 dysfunction)	6.45%	0	NS	Metastasis (77, 29.5%), meningioma (58, 22%), vestibular schwannoma (46, 17.8%). 5 NOT STATED	175 GTR, 85 STR, 2 biopsy
Zhang et al. (2022)9	682	136	7	39.14	3 (4)	3–72 months	2	VPS (2)	NS	28.57%	NS	NS	VS (1), astrocytoma (3), choroid plexus papilloma (1), ganglioglioma (1), medulloblastoma (1)	GTR (4), STR (3)

Abbreviations: CN, cranial nerve; CPA, cerebellopontine angle; CSF, cerebrospinal fluid; CVA, cerebral vascular accident; GTR, gross total resection; HCP, hydrocephalus; IVH, intraventricular hemorrhage; NF2, neurofibromatosis type 2; NS, not stated; PFT, posterior fossa tumor; STR, subtotal resection; VPS, ventriculoperitoneal shunt; VS, vestibular schwannoma.

In all, 19.79% (429/2168) of adult PFTs presented with preoperative hydrocephalus, of which 86.01% (369/429) were managed initially with a preoperative/intraoperative EVD, of which 16.26% (60/369) were found to have postoperative hydrocephalus on CT or MR imaging, which required a VPS to be inserted.

Five patient cohorts did not report complication details of patient cases requiring further CSF diversion, after undergoing preoperative EVD and tumor resection.^8,9,30,31,33 One patient cohort,³² reporting a failure rate of 31.62% (37/117), reported an additional case which developed a postoperative intraventricular hemorrhage and required further surgical intervention; however, the patient did not report further CSF diversion management.

Ventriculoperitoneal Shunt

The use of ventriculoperitoneal shunting for preoperative CSF diversion in adult PFTs was found in 5 patient cohorts^{30–32,34,35} between years 1981 and 2013, with a total of 618 surgically managed adult PFT cases as shown in Table 4. Sheikh and Kanaan³⁵ reported an average age of 26.70 years (17–39 years), of which 47.06% (290/618) were female. The remaining 4 patient cohorts did not state the average age range or male:female ratio.^30–32,34

Table 4.

Systematic Review: Cerebrospinal Fluid Diversion Using Ventriculoperitoneal Shunt Outcomes in Adults Prior to Posterior Fossa Tumor Resection

Reference	Total adult PFT cases (N)	Preoperative HCP cases (N)	CSF diversion cases (N)	Age (years)	Male (female) (N)	Follow-up	Postoperative HCP (N)	CSF drainage failure (N)	Details of failure	Failure rate (%)	Postoperative complications (N)	Anatomical location	Histopathology of tumor	Extent of tumor resection (N or %)
Atlas et al. (1996)32	104	2	2	54	NS	12–48 months	NS	0	0	0%	0	CPA	VS	33% GTR
Fukuda et al. (2007)34	68	16	4	55.25	1 (3)	50 months	0	0	0	0%	NS	CPA	VS	NS
Pirouzmand et al. (2001)30	284	39	4	48.5	2 (2)	6–120 months	NS	0	0	0%	Lower CN palsy, seizure, pseudo meningocele, MI	CPA	VS (2), Cavernous hemangioma (1), meningioma (1)	NS
Prabhuraj et al. (2017)31	145	70	70	39.31	42 (28)	6 months	NS	0	0	0%	Morbidity: 14 (NS details)	CPA	VS	NS
Sheikh and Kanaan (1994)35	17	12	7	26.14	1 (6)	12–109 months	0	0	0	0%	1 × persistent mild hemiparesis, 4 × tumor recurrence	Cerebellum	Medulloblastoma (7)	NS

Abbreviations: CN, cranial nerve; CPA, cerebellopontine angle; CSF, cerebrospinal fluid; GTR, gross total resection; HCP, hydrocephalus; MI, myocardial infarction; NS, not stated; PFT, posterior fossa tumor; VS, vestibular schwannoma.

In all, 22.49% (139/618) of adult PFTs presented with preoperative hydrocephalus; 62.59% (87/139) were managed initially with a preoperative/intraoperative VPS, of which 0% were found to have postoperative hydrocephalus on CT or MR imaging, and as a result, 0% required postoperative CSF diversion management, and the resultant preoperative VPS failure rate remained 0% (0/87), indicating a complete absence of complications.

Discussion

Although PFTs in the adult population are more common than in children, studies on pre-resection CSF diversion remain limited. To the best of our knowledge, this is the first systematic review of adult PFTs undergoing pre-resection CSF diversion in the form of ETV, EVD, or ventriculoperitoneal shunting. In our systematic review, we show that the frequency of hydrocephalus in surgically managed adult PFT is 22.98% (684/2976), and persistent hydrocephalus following preoperative CSF diversion is 13.63% (78/572). Between years 1992 and 2020, we determined a pre-resection ETV failure rate of 14.66% (17/116). To manage the ETV failure rate, 82.35% (14/17) underwent VPS insertion, 11.76% (2/17) underwent a right-sided EVD, and 5.88% (1/17) underwent an ETV re-do. Between years 1986 and 2021, we determined a pre-resection EVD failure rate of 16.26% (60/369), all of which underwent VPS insertion. Finally, between years 1981 and 2013, our pre-resection VPS failure rate was 0% (0/87).

Endoscopic Third Ventriculostomy

In cases of obstructive hydrocephalus, ETV represents an alternative to permanent shunts, allowing CSF to be internally diverted to the basal cisterns and eventually be reabsorbed by arachnoid granulations. Although it is minimally invasive and avoids many implant complications associated with alternatives such as VPS and EVD, the success rate of ETV is significantly variable in the adult population.³⁶ The ETV success score³⁷ is a validated clinical prediction rule, allowing for the approximation of operative success in the pediatric population. Although, more recently, it has been validated in a mixed population that includes adults, there is limited application on predictive factors specific to the older population.³⁸

Our review showed an ETV failure rate of 14.66% (17/116), requiring a second procedure in the postoperative period. ETV may fail from either an obstructive or communicating cause. In addition to CSF diversion, an EVD arguably facilitates clearance of blood clots and debris which may otherwise eventually obstruct the arachnoid granulations, potentially preventing communicating hydrocephalus in the longer term. ETV requires appropriate training to reduce the risks including injury to the basilar artery⁵; especially when the prepontine cistern is significantly reduced either by tumor⁶ or corresponding edematous mass effect from a resultant decreased space between the brainstem and clivus. A limited understanding of the anatomy and opening of the Lilliquist membrane can also exponentially increase the ETV failure rate.

Additionally, with an increased risk of intraventricular hemorrhage, there remains an increased risk of requiring permanent CSF diversion.³³ Closure of the stoma is a known complication of ETV, with hypotheses including tumor spreading, scarring phenomena, and the “snow-globe effect” related to the surgical position of PFT resection.³⁹ A lower rate of ETV efficacy correlated with prone positioning of PFT resection, in comparison to studies reporting sitting position; hypothesize that gravitational changes occurring from the prone position may contribute to stoma occlusion from blood clot deposition.³⁹

ETV in adult PFT resection has gained popularity as a first-line therapy to treat and prevent postoperative hydrocephalus.⁸ Our inclusion criteria assessed ETV alone, although endoscopic treatment enables the operating surgeon to perform adjunctive procedures, such as septostomy, foraminoplasty, and aqueductoplasty, further improving intracranial hemodynamics.²⁷ Our systematic review provides the first adult-only cohort data in the literature, but we were unable to reduce the number of ETV failure false positives due to, for example, a lack of detailed analysis of tumor entities, additional procedural factors including the opening of the Lilliquist membrane, and being unable to objectively determine the patency of the ETV on follow-up MR imaging and additional endoscopic CSF ventricular access procedures such as septostomy.

External Ventricular Drain

In a patient presenting with acute hydrocephalus, management of the associated hydrocephalus remains a critical priority. The use of an EVD, when compared to ETV and VPS insertion in the perioperative period, is the most efficient option for successful CSF diversion³⁹ and can be performed by every grade of neurosurgeon with a low rate of complications. When compared to ETV and VPS, EVD is the only cranial CSF diversion procedure that allows for continued monitoring of CSF dynamics. However, our systematic review found a pre-resection EVD failure rate of 16.26% (60/369), all of which underwent VPS insertion. In addition to protection against postoperative hydrocephalus, perioperative EVD placement, when optimally titrated, minimizes the risk of tentorial herniation and allows a more accurate control of the amount of CSF drained.^8,25,40

In our patient cohorts, due to heterogeneity within the data, we were unable to differentiate between prophylactic CSF diversion via an EVD and those requiring an EVD due to preoperative hydrocephalus. Won et al.²⁵ assessed the need for prophylactic perioperative EVD using an Evan Ratio of >0.3, surgeon preference, and a self-developed novel grading system. The use of prophylactic EVD attracts its own risks, including upward cerebellar herniation, hemorrhage, and infection.^7,8,25,41 The routine use of an antibiotic-impregnated catheter reduces the risk of infection in EVDs.^42,43

Perioperative EVD placement may increase the risk of persistent hydrocephalus.^44,45 Influencing factors include the duration of EVD placement, whether the EVD is on volume drainage, and the EVD setting. A correlation between the duration of EVD placement and the need for VPS has been described. A single-center retrospective study in a pediatric cohort found a mean time for EVD placement requiring definitive ventriculoperitoneal shunting of 5.8 days, compared with 4.3 days for patients not requiring a VPS.⁴⁴ Most recently, an adult population single-center study assessed EVD weaning and found the rate of ventriculoperitoneal shunting requirement was higher in patients with a prolonged weaning exceeding 15 days.³³ It has been reported that post-resection ETV has been effective in cases of EVD weaning failure, as an alternative to permanent shunt placement.^6,8 Further prospective studies to determine the optimum parameters of EVD use, including weaning time, and use of continuous versus volume drainage in these patients to clear surgical debris, may reduce the pre-resection EVD failure rate.

Ventriculoperitoneal Shunt

Permanent shunting is commonly considered the main treatment as shunt dependency is common.¹¹ Our systematic review found a VPS failure rate of 0% (0/87), with no patient cohort reporting a need for shunt revision or re-insertion, between 1981 and 2013. In a retrospective cohort of 123 pediatric patients with pre-resection ventriculoperitoneal shunting, there was immediate resolution of papilledema in 79% of cases, compared with 30% of those who did not have a VPS.⁴⁶ The study also reported that 30.75% remained permanently shunt-free following pre-resection ventriculoperitoneal shunting.⁴⁶ Few shunts require removal once placed. Although a VPS failure rate of 0% is found in the adult cohort during follow-up, the proportion of these cases that continue to have a functioning shunt in situ after tumor removal is not known. One pre-resection VPS adult patient cohort reported a morbidity rate of 20% (14/70) which did not result in a shunt revision or further CSF diversion procedure; however, the patient did not report specific morbidity details over a 6-month follow-up period.³¹

Although VPS cohorts showed no shunt revision pre-resection, later complications requiring later revision included shunt infection, shunt obstruction, and shunt dislocation.⁸ Shunt infection ranged between 1.2% and 19% and presents a clear risk of mortality.⁴⁷

In the context of pre-resection VPS with a PFT, additional surgical risks and complications need to be considered, including the risk of tumor movement close to the brainstem and a possible increased risk of intratumoral hemorrhage,^41,48–50 which may subsequently increase the risk of postoperative communicative hydrocephalus.³³ Our VPS patient cohort reported 4 tumor recurrences,³⁵ although not reported by this study, it may increase the risk of metastasis along shunt catheters.^51,52 Unlike an EVD with the facility to regulate the amount of CSF drained, a VPS system may be associated with greater vulnerability to upward tentorial herniation.^41,48–50

Although the VPS failure rate was found to be 0%, obstructive hydrocephalus may spontaneously resolve following tumor resection, indicating that in some cases nonpermanent CSF diversion in the form of an EVD or ETV may be satisfactory in patients at high risk of postoperative development of hydrocephalus.

Limitations

The conclusions of our systematic review are limited by the retrospective nature of the study and the paucity of data on pre-resection CSF drainage outcomes in adult PFT resection in comparison to pediatric studies. As a result, the sample size and lack of independent patient data were too small for robust statistical analysis.

The pre-resection ETV cohort consisted of patients between 1992 and 2020, followed by the pre-resection EVD cohort between 1986 and 2021, and finally the pre-resection VPS cohort between 1981 and 2013. Although all 3 CSF diversion groups demonstrate change in the neurosurgical management of these particular cases over the years and included patients of consecutive series, the comparison analysis was hindered by differing timelines. Additionally, endoscopy is a relatively new concept when compared to the VPS and EVD insertion skill set, with different procedures included within its scope (such as septostomy), and as a result, there is limited retrospective data.

Significantly differing and limited data on tumor characteristics, including histopathology, tumor location, size, and extent of resection, impaired our ability to compare the influence of this important variable on pre-resection CSF diversion techniques and outcomes.

Additionally, there were no standard criteria to select which patients received a pre-resection EVD, ETV, or VPS, and the choice of treatment modality was mainly based on unit and operating surgeon preference due to varying patient presentation and significant heterogeneity regarding tumor characteristics. This, however, reflects the diversity of presentation in clinical practice and thus enabled us to appreciate the difficulties encountered in decision-making.

It should also be noted that in this study we encountered limitations in the available data that precluded the measurements of additional covariates. Although we recognize the potential influence of various factors on the observed outcomes and complication rates, such as demographic characteristics, medical interventions (improvements in surgical and anesthetic techniques), and passage of time, we were unable to incorporate them into our analysis. Supplementary covariates would provide us with deeper insights regarding the efficacy of these 3 techniques. This impacts the generalizability of our findings and future explorations with more extensive data would provide a more comprehensive understanding of the role of these covariates.

Although we endeavored to define parameters for clinical hydrocephalus and radiological ventriculomegaly, the definition of hydrocephalus by other authors was not uniform. Some cohorts relied on symptoms and radiological findings,³² while others used radiological criteria alone.⁸ Some did not incorporate a clear definition.

We were unable to evaluate surgical positioning, long-term follow-up for individual patient data, radiological predictors such as perilesional edema or transependymal CSF outflow, and importantly, confounding factors for recurrent hydrocephalus, such as frequency of meningitis, CSF leak, and presence of pseudo-meningocele due to the paucity of data.

The lack of follow-up data limits our ability to understand the effectiveness of the CSF diversion procedures; the nature of a PFT, either malignant or benign, can itself have an impact on survival. Regardless, radiological follow-up for the tumor is a separate entity to assess the ventricular size. As a patient with a VPS is subject to further radiological investigation when admitted to the hospital when compared to a patient without one, this has the potential to bias the availability of follow-up radiological data in favor of shunt patients.

This is the first study to systematically review the role of CSF diversion procedures in adult PFTs, bringing together the evidence upon which to base treatment decisions. It enables surgeons to supplement their clinical practice with improved evidence, and to better inform preoperative discussion with their adult patients with PFTs, to reach a shared decision regarding the optimum treatment.

Conclusions

This paper is the first systematic review of adult PFT undergoing pre-resection CSF diversion in the form of ETV, EVD, or ventriculoperitoneal shunting. Ventriculoperitoneal shunting is the preoperative surgical technique that is related to the lower failure rate of postoperative hydrocephalus persistence/management. Nevertheless, the heterogeneity of the patient cohorts, reporting of the complications, short follow-up periods, and surgical expertise required for each surgical technique should be taken into consideration alongside the failure rates when a perioperative CSF diversion is considered for an adult patient presenting with this common clinical problem.

Supplementary material

Supplementary material is available online at Neuro-Oncology Practice (https://academic.oup.com/nop).

Conflict of interest statement

None declared.

Funding

No funding was received.

Authorship statement

A.V.—Writing—original draft, review and editing, formal analysis. A.B.M.—Conceptualization, methodology, data curation, writing—original draft. F.A.—Investigation, data curation. A.I.—Investigation, data curation. C.S.—Investigation, formal analysis. A.K.K.—Investigation. J.P.L., B.V., J.R.P.—Supervision and review.

Data Availability

Subject upon request.