Management of Pediatric Cavum Cysts: A Scoping Review and a Single Institution Case Series

Abstract Introduction: Pediatric cavum cysts are a rare yet complicated pathology to manage. The literature is scarce, primarily consisting of case series, and lacking a consensus regarding clear management. In this scoping review, we aimed to compile existing information in the literature regarding the management of pediatric cavum cysts across the last 10 years. We also present our management of 19 patients, the largest case series to date, highlighting knowledge gaps surrounding the management of this salient pathology. Methods: A literature search using PubMed and SCOPUS was conducted using the following search terms: (pediatric) AND (Cavum septum pellucidum) OR (cavum vergae) OR (cavum velum interpositum) AND (management). Eligibility criteria included peer-reviewed publication published in the last 10 years, pediatric population, cavum cyst, and English language. A retrospective search was conducted for all pediatric cavum cysts between 2013 and 2023 at our institution. Clinical and radiographic characteristics as well as intervention and outcome data were collected for both the scoping review and our cases. Results: 330 total articles were populated using our search. 12 articles met our inclusion criteria. 41.7% (n = 5) of the articles were case series, 33.3% (n = 4) were case reports, 8.3% (n = 1) was a technical article, 8.3% (n = 1) was a systematic review, and 8.3% (n = 1) was a case questionnaire. Resolution of symptoms was noted in all articles of our scoping review, regardless of treatment modality. The average age in our case series was 9.84 years old and average age at diagnosis was 5.53 years old. 6 patients (31.6%) were female and 13 patients (68.4%) were male. 2 out of the 19 patients (10.5%) were surgically treated. Conclusion: There is no clear consensus on the management of cavum cysts. A prospective, multicenter study is needed to create standardized pediatric cyst management guidelines. The current thought is that surgical intervention should be saved for those patients with obstructive hydrocephalus and signs of intracranial hypertension.


Introduction
Surgical proficiency, rigorous scientifically supported surgical guidelines, and a broad deftness with medical decision-making are the hallmarks of pediatric neurosurgical care.The current pediatric neurosurgical literature does not offer clear guidelines on the pediatric management of cavum septum pellucidum cysts.Given the anatomic complexity of operating on such eloquent central nervous system (CNS) structures and the patient population who range in age from neonate to late teen, guidelines are overdue.
While cavum septum pellucidum cysts and the unique surgical approaches to this rare pathology have been described in the literature, there are currently no defined guidelines for pediatric neurosurgical management of this uncommon pathology.This ultimately leads to inconsistent practices at regional and national level due to the gap of available information.
Here, we report on the past 10 years' worth of midline intracranial cysts with attention to cavum septum pellucidum cyst at a single institution as well as a scoping review of the literature to synthesize the symptomology, management, and outcomes of patients suffering from this pathology.Our scoping review was written to synthesize the existing information and provide a means to overcome knowledge gaps in the surgical management of such pediatric midline cysts.

Literature Search
We conducted a comprehensive literature review on PubMed and SCOPUS using the following fields relating to pediatric intracranial cysts: (pediatric) AND (Cavum septum pellucidum) OR (cavum vergae) OR (cavum velum interpositum) AND (management).All articles populated were screened based on our eligibility criteria.Our eligibility criteria included peer-reviewed publication published in the past 10 years, pediatric population, midline intracranial cyst, English language, and relevance.Exclusion criteria included non-English language, adult population, over 10 years old, non-peer-reviewed publications, and publications featuring intracranial cysts other than pediatric midline cysts.
Microsoft Excel was used for data collection.Data collection was conducted by one of the authors (HER).The variables we collected include author, year, journal, location, number of patients, average age, comorbidities, treatment method, follow-up period, imaging used, outcomes, recommendations, limitations, and future directions.The data collected was double-checked for errors.

Institutional Data
We then reviewed medical record numbers for every patient less than 18 years of age who was diagnosed with an intracranial cyst in the past 10 years at our institution.Inclusion criteria include pediatric age and the diagnosis of either a cavum septum pellucidum cyst, cavum vergae cyst, or cavum velum interpositum cyst.Patient data were then de-identified to ensure confidentiality.This retrospective study was approved by the Medical University of South Carolina's Institutional Review Board and Ethics Committee.
We then collected data on cyst management from our institution using a form on REDCap.Objective information collected included current age, age at diagnosis, sex, comorbidities, diagnosis, imaging modality, image timing (prenatal or postnatal), and treatment.Outcomes were determined by improvement of symptoms and resolution of (CSF) obstruction with adequate flow.

Data Analysis
Descriptive statistics was collected for all data collected using SPSS.The data from the scoping review were then compared to the descriptive statistics from our institutional data.

Results
Nineteen total articles were initially populated using our PubMed search.Nine out of the 19 articles met inclusion criteria.One article was excluded because of non-English language, 5 were excluded because of patient age, and 4 were excluded because of relevance.Of the 9 articles that met criteria, three were case reports, three were case series, one was a survey questionnaire, and one was a systematic review.They were all published between 2013 and 2023.The SCOPUS review originally populated 311 articles.After filtering for inclusion criteria, 10 articles remained.Out of these 10 articles, 7 were crossreferenced with the PubMed search.Out of the three additional articles, two were case reports and one was a technical article.Utilizing both databases, the scoping review totaled 12 articles relevant to the management of pediatric anterior midline cysts shown in Figure 1.
The number of pediatric patients featured in the literature ranged from 1 to 26.Ages ranged from 5 months to 16 years old.Our scoping review includes cases from China, Israel, Nepal, Germany, India, Czech Republic, Australia, Singapore, Brazil, Poland, and Italy.Eleven out of the 12 (91.7%)articles featured in our scoping review featured cases of cavum septum pellucidum cysts.Two articles (16.7%) featured cases of cavum septum interpositum cysts.Four articles (33.3%) featured cases of cavum vergae cysts.Presenting symptoms noted in the literature were headache, nausea, vomiting, seizures, hydrocephalus, speech impairment, developmental delay, psychiatric, decline in school performance, and visual disturbance.Noted comorbidities included Wilson's disease, Peters-plus syndrome, prematurity, and X-linked adrenoleukodystrophy. Eight out of the twelve articles in our scoping review presented cases of endoscopic fenestration for the treatment of anterior midline cysts.Two articles presented cases of conservative management, one article presented a case of intraventricular septostomy Management of Pediatric Cavum Cysts and right foraminoplasty, and one article was a survey sent out to 89 neurosurgeons inquiring about their plan of care.Resolution of symptoms was noted within each paper reviewed, regardless of the treatment modality.A summary of the management of midline cysts in the literature is shown in Table 1.

Case Series
After obtaining IRB approval, a retrospective search for intracranial cysts using our hospital's radiology database was conducted.Seventy-one total studies were populated.After excluding all other arachnoid cysts and adults, the cohort was narrowed to 19 midline cyst patients.Ages ranged from 1 year old to 17 years old.The average current age of in this patient cohort was 9.84 years old and average age at diagnosis was 5.53 years old.6 patients (31.6%) were female and 13 patients (68.4%) were male.
Six patients (31.6%) in the case series were diagnosed with a septum pellucidum cyst.13 patients (68.4%) were diagnosed with cavum velum interpositum cyst.While all patients had MRI to confirm initial diagnosis, some patients had either computed tomography (CT) or US that identified the cyst that was subsequently investigated with MRI.Fast brain MRI (fbMRI) was used in 7 of the patients (36.8%), while ultrasound was used in 4 patients (21.1%) and CT was used in 2 patients (10.5%).Finally, 4 patients were diagnosed prenatally (21.1%) and 15 patients were diagnosed postnatally (78.9%).Five (26.3%) of the patients initially presented with seizures.Additionally, 5 patients (26.3%) were found to have their intracranial cyst during prenatal ultrasound screening.Four patients (21%) initially presented with headache and two (10.5%)presented with macrocephaly.Two (10.5%) patients found their cysts incidentally and 1 patient presented with hemiparesis (5.3%).Two patients (10.5%) underwent endoscopic fenestration and 17 (89.5%)were treated conservatively with close followup.Both patients that underwent endoscopic fenestration presented with severe headaches.Additionally, 1 of the patients also experienced episodes of emesis and photophobia.Both patients were diagnosed with cavum septum pellucidum cysts and experienced hydrocephalus due to the cyst obstructing CSF flow.After surgical treatment, both patients regained proper CSF flow (Fig. 2).Although both patients still experienced headaches, they were less severe and less frequent.Pre-operative (Fig. 2a) and post-operative (Fig. 2b) images of the first patient who underwent endoscopic fenestration and preoperative (Fig. 2c) and postoperative (Fig. 2d) images of the second patient who underwent endoscopic fenestration at our center are shown in Figure 2.
Eight (42.1%) of our patients experienced clinical improvement, seven (36.8%) remained clinically stable, and 1 patient (5.3%) worsened clinically.Three (15.8%) of the patients were lost to follow-up.Additionally, three (15.8%) of our patients who were closely monitored had spontaneous resolution of their cysts.Among these 3 patients, one (5.3%)presented with seizures, one (5.3%)was an incidental finding, and one (5.3%)was found during a prenatal ultrasound screening.Two of these patients (67%) suffered from comorbid hydrocephalus.One of the patients also had comorbid congenital intellectual disabilities and endocrine disorders.The other patient had congenital CNS defects as well as genetic disorders.Only 1 of these patients had no comorbidities.Full descriptive statistics of our patient cohort is shown in Table 2.

Discussion
This scoping review and case series summarizes all current literature regarding the management of pediatric midline intracranial cysts and adds a robust account of the management of these cysts from a lone institution, this represents the largest case series to date.We identify a lack of consensus on the management of pediatric midline cysts.Additionally, we were able to describe the common presenting clinical characteristics seen in patients with pediatric midline cysts.Given the lack of consensus in the pediatric management of this pathology, we are also able to provide our clinical reasoning for radiologic follow-up, when to offer surgical treatment, and discuss in the context of what is available in the literature.Finally, we discuss recent advances in neuroradiology and potential implications for the management of patients who present with pediatric midline cysts.
Historically, anterior midline cysts arise from one of three entities: the cavum septum pellucidum, cavum vergae, or cavum velum interpositum [13].Cavum septum pellucidum is defined as a cystic lesion that develops between the two leaflets of the septum pellucidum [14].A cavum septum pellucidum is normal during embryogenesis, but greater than 85% of the time, the leaflets will fuse together after birth [15].Cavum septum pellucidum cysts can still be seen in about 20% of the population and are reported to be linked to psychiatric conditions and traumatic brain injury [6,13,16,17].Cavum vergae cysts, which occur posteriorly to cavum septum pellucidum, can also be seen in about 30% of newborns [13].However, the prevalence in adulthood is much lower than cavum septum pellucidum, at less than 1% [13].Although cavum septum pellucidum and cavum vergae are anatomically attached, cysts of either can occur in isolation as well as together [14].A cavum septum interpositum is defined as a cystic lesion in the subarachnoid space between the fornix and the choroid plexus [13].Similarly to the other anterior midline cysts, cavum septum interpositum is usually seen in newborns [18].Given that anterior midline cysts can be neurodevelopmental, there are many reports of comorbid genetic disorders, intellectual dis-ability, seizures, and neuropsychiatric disorders [19].This is seen in our reported series where 10.6% (n = 2) of patients had either a congenital heart or CNS defect, 26.3% (n = 5) have intellectual disability, and 15.8% (n = 3) had other genetic conditions (Table 2).Although many anterior midline cysts are found incidentally, some present with symptoms of increased intracranial pressure, vomiting, nausea, headaches, and developmental delay [8,19].In severe cases, anterior midline cysts can cause obstructive hydrocephalus [5,8,13].Endoscopic fenestration of cysts that cause obstructive hydrocephalus has shown to be safe and effective, both in the literature [1,5,8,13] and in this series (Table 2).Additionally, most cases in the literature as well as our own, opted for conservative management for cysts that were found incidentally, were asymptomatic, or had very benign symptoms.One study tried to understand the management by sending a questionnaire regarding management of a 10-year-old patient presenting with headaches and difficulty concentrating to 54 neurosurgeons around the world asking how they would manage the case [4].Given the benign symptoms, 50% of the neurosurgeons indicated they would watch the patient conservatively.Adding persisting symptoms to the scenario, 58% of the neurosurgeons indicated they would monitor intracranial pressure (ICP).Ninety-one percentage of the surgeons in their questionnaire noted evidence of increased ICP as adequate indication for surgical treatment.Ninetyeight percentage of surgeons noted their preferred choice of surgical management would be endoscopic fenestration [4].There is, however, a lack of consensus regarding treatment for patients who do not have obstructive hydrocephalus or increased ICP, but present with "intermediate" symptoms such as severe headaches, seizures, intellectual disabilities, or enlarging cysts without change in symptoms.
One reason for hesitancy to offer surgery to those with "intermediate" symptoms is that surgery may or may not resolve symptoms.Surgery also involves risk of new neurological deficits, infection, and the need for re-do surgery.Additionally, there have been cases, both in the literature (5.6% of patients) and of our own (15.8% of patients), where conservative treatment of patients presenting with more advanced symptoms such as seizures, hydrocephalus, nausea, and vomiting had spontaneous resolution of their symptoms including reduction in the size of the cyst (Table 2) [2,6].Additionally, complex comorbidities can complicate clinical decision-making [6].This complexity is reflected in a case published by Khatri et al. [6] that demonstrated successful conservative management of a patient with an anterior midline cyst and comorbid Peter plus syndrome, a syndrome that can also present with increased ICP.On the contrary, surgical treatment in the absence of increased ICP and/or hydrocephalus can be offered preemptively if there is concern for cyst enlargement that may pose a future threat.Frequent, closely scheduled follow-up imaging and clinical exams can aid in the decision to continue conservative treatment or offer surgical treatment.
In the literature, postoperative imaging has routinely been vis-a-vis MRI [3,[5][6][7][9][10][11][12].One issue that can arise when trying to serially follow the pediatric population is the inability to reliably obtain MRI scans due to hyperactive children and the need for sedation [20].This concern can be further exacerbated in children who have comorbid genetic and developmental disabilities.One way that this factor may be mitigated in the management of patients with anterior midline cysts requiring close follow-up is through the use of fbMRI [20].Regardless of which imaging modality first identified the cystic lesion (ultrasound, CT, MRI), the diagnosis should be confirmed with an MRI of the brain with and without contrast.In this series, once clinical exam and surgical evaluation were established, patients were scheduled for close clinical and radiographic follow-up, using fbMRI.At our institution, patients returned for fbMRI every 3 months for a total of two scans, then every 6 months for two scans, and finally once a year for three scans or if asymptomatic.The use of fbMRI allowed for us to get continued follow-up data without the need for general anesthesia due to the short duration needed for this unique MRI sequence.This is an especially important option for toddlers and infants that may require having to undergo general anesthesia for a full MRI sequence, as well as following patients who have a high risk of their cavum cyst becoming symptomatic and subsequently developing pressure active hydrocephalus.The availability of imaging modalities like fbMRI could potentially influence the clinical decision-making on whether a patient is offered surgery.Having the option to radiographically follow pediatric patients frequently with a fast, and well tolerated imaging modality might provide reassurance that if any significant cyst enlargement of ventricular change occur, it would be caught radiographically before serious symptoms, such as uncompensated hydrocephalus, developed.
Although neurosurgeons can utilize additional tests such as ICP monitoring and fbMRI to help guide their decision to offer surgery or not, further analysis is needed for these "intermediate" patients who are presenting without increased ICP, but still have detrimental symptoms.A prospective, multicenter study is needed to create standardized pediatric cyst management guidelines.

Conclusion
In this scoping review, we offer the most up-to-date description of those diagnosed with pediatric anterior midline intracranial cyst and provide the largest case series in the literature.We described 19 total patients who were treated for a pediatric midline cyst between the years 2013 and 2023.Of this cohort, only two required surgery.In our institution's case series, of the 2 patients who underwent endoscopic fenestration both presented clinical and radiographic signs of obstructive hydrocephalus; all others were conservatively followed with fbMRI.

Statement of Ethics
This study protocol was reviewed and approved by the Medical University of South Carolina Institutional Review Board Committee, approval number (Pro00121179).Additionally, the MUSC IRB Committee granted exemption from requiring written informed consent.

Fig. 2 .
Fig. 2. Preoperative (a) and postoperative (b) images of the first patient who underwent endoscopic fenestration and preoperative (c) and postoperative (d) images of the second patient who underwent endoscopic fenestration at our center.