A retrospective case cohort study of managements and outcomes of pediatric patients with intracranial arachnoid cysts

Abstract

Background: Intracranial arachnoid cysts are benign developmental lesions with CSF-like fluid collection inside. As the exact pathogenesis and natural history are still unclear, there has been no treatment guideline of intracranial arachnoid cysts so far.

Methods: We have analyzed medical records of pediatric patients below the age of 14 years old with intracranial arachnoid cysts managed in our department from January 2011 to September 2016. A total of 134 cases were enrolled in this study. We have investigated and discussed the clinical data with a literature review. 

Results: 134 pediatric patients were admitted in our department in the past 5 years, aged 1 month-14 years (averaged 5.3 years). Surgeries were performed in 91 cases, of which 71 cases underwent cyst fenestration or resection, 17 cases received cystoperitoneal shunt and 3 cases underwent subdural drainage. 70 cases (77%) were symptom-free after surgeries or had minor complaints at follow-up. Notably, 9 cases (6 cases under 2 years old, 3 cases older than 2 years old) undergoing prior cyst fenestration or resection developed hydrocephalus and/or subdural hygroma that necessitated secondary shunt surgeries, and 2 cases treated with primary CP shunt developed shunt dependency 2 and 4 years later respectively, which was resolved by keyhole resection of the shrunken cyst walls. 18/23 children with giant intracranial arachnoid cysts who were diagnosed incidentally without any definite symptom had satisfactory outcomes after surgical interventions. 

Conclusions: CP shunt with a programmable valve is recommended for patients aged 2 years or below with giant arachnoid cysts. Shunt dependency syndrome after CP shunt could be resolved by minimally invasive resection of the shrunken cyst wall. Giant intracranial arachnoid cysts, even lack of symptoms, could be considered for surgical interventions.

Background

IACs are congenital and benign lesions with CSF-like fluid collection inside.There is no consensus in treatment approaches for an effective management. Manifestations such as neurological deficits, intracranial hypertension, seizures due to expansion or mass effect of the cyst are suggested as indications for neurosurgical interventions [1–6]. A survey of neurosurgeons has suggested that surgical managements were also preferred for asymptomatic huge cysts or growing cysts without any symptoms in order to improve brain development or avoid skull malformation [4, 5, 7]. Regarding the operative modalities, some authors believed that the failure rate of cyst resection or fenestration was much higher in children under 3 years old and additional shunts might be required to relieve symptoms [6, 8–10]. In reality, subdural fluid collection, subdural hematoma, hydrocephalus, CSF leakage, cyst re-growth and the need of additional operations after cyst resection or fenestration might occur in any age group [3, 6, 10–12]. Therefore, CP shunt is recommended in the treatment of arachnoid cyst due to high complication incidence following cyst resection or fenestration, especially in young children [9, 11, 13, 14], even though the risks of infection, obstruction and over-drainage cannot be excluded [15, 16]. In the current study, we have retrospectively studied the clinical data of pediatric patients below the age of 14 years old with IACs treated in our department from 2011 to 2016. Our objective was to correlate the clinical characteristics with optimal surgical choices.

Methods

We have retrospectively analyzed patients with IACs (cysts secondary to brain trauma or infection and patients with other comorbid congenital anomalies were excluded) treated in the neurosurgery department of Tongji Hospital, Huazhong University of Science and Technology, Wuhan, China, from January 2011 to September 2016. A total of 134 pediatric patients younger than 14 years old were enrolled in this study. Clinical data such as age, sex, presenting symptoms, radiological findings, treatment modalities, complications and outcomes based on medical records and findings at follow-up of 24 months on average were investigated. This study was approved by institutional review board of Tongji Hospital, Tongji Medical College.

Results

Patient population

Of the 134 pediatric patients studied, the ratio of male to female was 4.4:1 (109/25) and their age ranged from 1 month to 14 years with an average of 5.3 years. Notably, the majority of them (77.6%, 104 of 134) were younger than 8 years old, compared to those (22.4%, 30 of 134) aged from 8 to 14 years old.

Symptomatic and Radiological examination

One-fourth of the patients (33/134) complained of headache or vomiting and a similar number of patients (38/134) presented with seizures. Other complaints included skull deformity (14/134), developmental delay (9/134) and neurological disorders (2/134, one squint, one eyesight drop), while 38 children were incidentally diagnosed with IACs (Figure 1a).

Radiological data of computerized tomography (CT) and magnetic resonance imaging (MRI) indicated that the cysts were mostly located at the temporal region (including frontotemporal region and temporal-parietal region, 111 of 134 cases), of which, 64 cases were in the left, 44 right and 3 occurred bilaterally. Other localized regions included: brain convexity (6), cerebellar region (6), suprasellar region (3), CPA (1), third ventricle (1), pineal region (3), septum pellucidum (1) and lateral ventricle (2) (Figure 1b).

Treatments and Outcomes

All patients who underwent neurosurgical interventions complained of definite symptoms which affected daily life or had presentations of increased intracranial pressure such as headache or skull deformity. Those patients who were initially suggested for observations would be considered for surgery when radiological cyst enlarging, development of new symptoms or worsening of the original minor symptoms occurred during regular follow-up.

Of the 134 patients, 91 (67.9%) cases had surgical management. Each case was carefully evaluated for operation strategies and detailed information of various surgical choices were presented to the families of each patient, and a decision was reached following informed discussion and additional support for any queries. The postoperative follow-up ranged from 3 to 56 months with a median time of 24 months. Radiological and clinical assessments were performed regularly during the follow-up. A “no change” referred to a change of IAC size of less than 20%. A reduction in size by more than 20% was defined as a “decreased” IAC. A “resolved” IAC meant that an IAC was almost undetectable on CT or MR images.

Initial surgeries primarily involved microsurgical cyst resection (66 cases, 72.5%), endoscopic cyst fenestration (5 cases, 5.4%), CP shunt (17 cases, 18.7%) and subdural drainage because of subdural fluid collection or hematoma after minor brain injury (3 cases, 3.3%) (Table 1). Notably, in the resection and fenestration group, there were 9 patients (9/71, 12.7%) who suffered from secondary subdural hygroma or hydrocephalus and required a secondary ventricular/subdural-peritoneal shunt due to intracranial hypertension manifesting as headache, vomiting, lethargy or bone flap bulging. 25 children with IACs younger than 2 years old underwent neurosurgical interventions: 14 cases underwent cyst resection or fenestration and 11 children received CP shunt. 6 cases with secondary subdural hygroma or hydrocephalus after cyst resection or fenestration (6 cases, 42.9%, 6/14) happened in this age group. Out of the 57 patients above the age of 2 years who received cyst resection or fenestration, only 3 cases developed obvious subdural hygroma or hydrocephalus (3 cases, 5.3%, 3/57) (Table 2). We defined subdural CSF collection with a maximal thickness exceeding 1cm and recorded the cyst size as the stated maximal anteroposterior, craniocaudal and mediolateral dimensions reported by the radiologists and calculated the volume by multiplying the dimensions (i.e. anteroposterior × craniocaudal × mediolateral). In these 9 children suffering from secondary subdural hygroma or hydrocephalus, the average preoperative cyst size was 146.32ml in patients younger than 2 years and 143.87ml in older children, which showed no statistical significance between the two groups. Therefore, for the two age groups, the incidence of subdural fluid collection or hydrocephalus as a complication of cyst resection or fenestration was significantly different (Chi-square test, P<0.005), which implied that microsurgical cyst resection or fenestration might not be the optimal choice of treatment for pediatric patients under 2 years old. We also took into consideration other factors such as preoperative midline shift, gender and cyst location, that might contribute to the secondary shunt procedures following initial cyst resection or fenestration, and found no statistical differences of these factors between the two age groups (Fisher’s exact probability test, midline shift, p>0.05; gender p> 0.05; cyst location, p>0.05).

Notably, an 11-month-old boy received successive subdural-peritoneal shunt and VP shunt after microsurgical cyst resection. Initially, a growing arachnoid cyst was detected in the left temporal region and the boy underwent microsurgical cyst resection. 11 days later, he experienced confusion and a CT scan revealed a large amount of subdural fluid collection causing a midline shift. A subdural-peritoneal shunt was subsequently placed. However, the patient developed symptoms related to increased intracranial pressure and the boy was diagnosed with hydrocephalus through a brain CT scan one month later. A VP shunt was performed with a Y-shaped way connection union used. The recovery was favorable during the postoperative follow-up period (Figure 2).

Outcomes in all the operated patients were mainly assessed by symptomatic resolution or radiological findings at a long-term follow-up. In the 91 (91/134, 67.9%) operated patients, consisting of 76 who were readily operated on and 15 delayed cases, the presenting symptoms and radiological findings were relieved or improved in 70 cases (70/91, 77%). In the cyst resection or fenestration group, 3 cases complained of no improvement of the original symptoms and no reduction of the initial cyst size. Another 3 cases were satisfied with a relief of symptoms with no significant change in radiological findings. One boy with a huge IAC in the third ventricle died after microsurgical cyst resection, which might have been caused by a serious injury to basilar vessels. 17 patients who were managed with CP shunt showed a relatively favorable outcome except for 2 cases (11.8%, 2/17) who developed shunt dependency syndrome, and 2 children (2/17, 11.8%) suffering from infection after CP shunt. Three cases undergoing drainage because of acute subdural effusion or hematoma after minor head injury reported excellent long-term prognosis without any cyst-related symptoms (Figure 3). 12 out of 43 non-surgical patients were found to be symptom free and 31 cases had tolerable symptoms. Notably, in our series, 23 patients were incidentally diagnosed with IACs with no definite symptoms. The common characteristics of the IACs were the massive volume size or emergence of mild midline shifts (0.5cm) caused by IACs. 6 patients received CP shunts and the others underwent microsurgical cyst resection or endoscopic fenestration. Cysts in 18 patients in the group were reduced by more than 20%. Four children underwent secondary subdural-peritoneal shunt or VP shunt due to subdural hygroma or hydrocephalus following the primary microsurgical cyst resection. No other new symptoms occurred and the shifted midline in 4 patients returned to the right position (Table 3).

2 out of 17 cases receiving CP shunt developed shunt dependency. A 4-month-old boy was incidentally diagnosed with an arachnoid cyst located at the left middle fossa and he presented with headache and vomiting 20 months later due to cyst growth. Another case was that of a 1-year-old girl who was examined under MR scan because of seizures and a huge arachnoid cyst was detected in the right temporal lobe (Figure 4). These two children underwent CP shunt as the initial treatment with a non-programmable valve of 70mmH₂O opening pressure. Both children later suffered from shunt dependency after 2 and 4 years respectively and manifested symptoms related to intermittently intracranial hypertension. Microsurgical cyst wall resection was attempted, and the cyst membrane was found to be dense and shrunken, partially covering the proximal end of the shunt catheter. The surrounding brain cortex appeared stiffened, noncompliant and vascularized by tiny pia blood vessels. The parietal cyst membrane was removed under microscope and the cyst thus opened to the subarachnoid space. The proximal end of the catheter was adjusted into the cyst cavity and fixed on the dura. For the boy, we used a new catheter with programmable valve with an opening pressure set at 70mmH₂O. We had to revise the proximal end of the original catheter for the girl due to economic concerns.

For the observation group, MR examinations were performed every six months or according to patients’ complaints and symptoms. Surgeries were ultimately performed in 15 out of the 58 (15/58, 25.9%) cases after periodical observations (3 cases with CP shunt, 11 cases with microsurgical cyst resection and one child with endoscopic cyst fenestration) (Table 4). Their manifestations included cysts enlarging in 11 cases, headache in 1 case, seizures in 1 patient, eyesight deterioration in 1 patient and 1 staggering gait (cyst enlargement being the main complaint, and the mean observation time was 160 days) (Figure 5). Two patients (a 6-year-old boy and a 13-year-old boy) experienced almost disappearance of the cysts after an observation period of about eight months.

Discussion

The exact prevalence and natural history of IACs remain unclear. In accordance with other reports, male dominance was significant in our series with the male to female ratio being 4.4:1 (109:25). With respect to the age prevalence, our 134 cases showed a higher age distribution under 8 years old, compared to those aged 9 to 14. However, another report by Al-Holou et al describing 309 pediatric patients with IACs, identified from a 11,738 children survey by MRI scanning, found no significant difference based on age distribution [2]. The discrepancy could be because most of our cases were symptomatic at hospitalization while the 309 cases of Al-Holou et al were screened from an asymptomatic population. Only a minority of asymptomatic arachnoid cysts would grow and develop symptoms at last, and even fewer children older than 4 years experienced cysts growth [2, 17]. However, of our 15 cases that were initially observed and then operated on for cyst enlarging or symptoms development, 7 (46.7%) were above 4 years old. Notably, the authors of the current study had ever treated 2 patients older than 60 years who had dramatically enlarged IACs and increased intracranial pressure and then underwent CP shunts (Data not presented). Together with the spontaneously disappeared IAC cases in our series, the exact natural history of IACs seemed unpredictable and elusive, and more data were needed to clarify it.

The treatment strategy of IAC patients was also a topic with controversial opinions. One of the controversies was the surgical indication for those patients with unspecific minor symptoms such as mild headache or dizziness. There was consensus that symptomatic IACs causing intracranial hypertension, seizure attacks or neurological deficits were recommended for surgeries. However, when referring to unspecific or minor symptoms, clinicians tended to select conservative therapy. In our study, in the group of patients with minor symptoms, the improvement after surgery was significant except for one case with postoperative shunt infection, one case developing shunt dependency syndrome and another one complaining of no relief of headache. Furthermore, 23 children in our series with giant IACs while presenting with no definite symptoms underwent surgical treatments, 18 of which experienced cyst volume reduction by more than 20% without any new symptoms. The results demonstrated that surgical managements might also be beneficial for children with large IACs with no or minor symptoms.

The potential rupture risk had been suggested as an indication for surgical treatment of asymptomatic IACs [4]. However, our three cases undergoing burr-hole drainage due to cyst rupture or hemorrhage after minor brain injuries achieved satisfactory outcomes without any neurological deficits and the cysts almost disappeared after burr-hole drainage. The favorable outcomes after surgeries due to posttraumatic cyst rupture or hemorrhage have also been reported by other authors [17], thus, the potential rupture risk might not necessarily be indicated for surgeries in children with asymptomatic IACs [2].

Another challenge in the treatment of IACs was the choice of optimal surgical approaches. In this series, 9 out of the 71 children receiving microsurgical or endoscopic fenestration suffered from apparent subdural fluid collection or hydrocephalus and underwent secondary shunt procedures, of which one child received sequential subdural-peritoneal and VP shunt. 6 of these 9 children were younger than 2 years old (P<0.005). Similarly, Kimiwada et al reported that they performed microsurgical or endoscopic fenestration for 4 children with IACs younger than 2 years old and 3 of them required secondary shunt [10]. Choi JW et al also found that in the case of infants, 67% patients suffered from operation failure after microsurgical or endoscopic procedures and the failure rate was much higher than the older cohort [6]. Additionally, Ciricillo SF et al showed that 67% cases (10 children, mean age 2.2 years old) who had received microsurgical resection of cyst wall or fenestration required CP or VP shunt [9]. The reason why young children were more prone to postoperative subdural hygroma or hydrocephalus might be related to immature CSF absorptive capability of arachnoid villi in this age group. Go KG et al revealed that the IAC wall had secretory function under scanning and transmission electron microscope [18], thus, subdural hygroma or hydrocephalus might develop immediately once the cyst was opened into the subarachnoid space in young patients with less capable CSF absorption. Therefore, we suggested CP shunt with programmable valve for patients younger than 2 years old, especially those with huge IACs.

Shunt dependency syndrome is considered to be a rare but serious complication of CP shunt. It was previously referred as slit ventricle syndrome, however, since ventricles were either normal or small when the syndrome developed, the name “shunt dependency syndrome” has since been widely accepted [15, 16]. Patients typically presented with irritability, agitation and headache, which could occur and be relieved unexpectedly. Some suffered from visual deficit, even complete blindness, which might improve from neurorestorative techniques [19]. 2 children with shunt dependency in our study were treated with microsurgical resection of the shrunken cyst wall. Because of the remarkably decreased cyst size after primary shunts, the shrunken cyst wall could be well visualized under the microscope after only slightly enlarging the burr hole where the primary shunt catheter was previously inserted. During the operation, the cyst membrane was found to be dense and significantly thickened and partially covering the catheter end, and the surrounding brain cortex looked moderately stiff and more vascularized by tiny pia blood vessels than the normal cortex. Under the microscope, the cyst wall could be easily removed including a portion of visceral membrane covering the cortex. The proposed pathogenesis of the syndrome might be the collapsed cyst wall intermittently obstructing the proximal catheter and the progressively decreased cerebral compliance due to chronic fibrosis [20, 21]. Regression of CSF absorption after shunt might also be involved [22]. Together with our experience, the keyhole resection of the collapsed cyst wall could be performed as a minimally-invasive, effective and economic treatment strategy for such patients. However, a longer follow-up period after the secondary cyst resection and an investigation of more cases were warranted.

Limitations of the study

The current study was to correlate the clinical characteristics with optimal surgical choices. However, it was with limitations. Firstly, the study was a retrospective and non-randomized review. Secondly, more patients especially those younger than 2 years old and undergoing endoscopic surgeries would have been included to support our conclusions. Moreover, SPECT scan, considered as an objective examination and suggested by some authors, could be adopted to evaluate post-surgery improvements. Furthermore, most of our cases presented with huge cysts and the quantity of those classified into Galassi II (5 patients) and Galassi I (2 patients) were much less, therefore, we had not grouped our cases according to Galassi classification.

Conclusions

Treatment strategies for pediatric IACs remained controversial. Cyst resection or fenestration in young children had a higher probability of postoperative subdural hygroma or hydrocephalus. We recommended CP shunt with programmable valve for young children (≤2 years old) with giant IACs. The keyhole resection of shrunken cyst wall proved to be helpful in resolving shunt dependency syndrome after primary shunt surgeries. For asymptomatic IACs with radiological mass effect, asymptomatic growing cysts, cysts with unspecific symptoms (e.g. headache, dizziness), surgeries usually led to radiological reduction of cyst volume and might be beneficial to neurological development or alleviation of primary symptoms. Larger cohort, randomized studies and more objective outcome evaluation methods would be needed to consolidate the conclusions.

Abbreviations

IAC: intracranial arachnoid cyst; CP: cystoperitoneal; CSF: cerebrospinal fluid SPECT: single-photon emission computed tomography; VP: ventricle-peritoneal

Declarations

Acknowledgements

Not applicable.

Authors’ contributions

FD: Protocol development, data analysis and report write up, SZ: Protocol development, data analysis and report write up, YL: data collection and data analysis, ZW: data collection and data analysis, ZC: protocol development, data analysis, FW and TL: research idea generation, data analysis and manuscript revision. All authors read and approved the final manuscript.

Funding

There is no funding source.

Availability of data and materials

Data are available from the corresponding author on reasonable requests.

Ethics approval and consent to participate

The entire study was approved by the Ethical Review Board of Tongji Hospital, Tongji Medical College and written consent was taken from parents or care takers.

Consent for publication

Not applicable.

Competing interests

The authors declare that they have no competing interests.

Author details

¹ Department of Neurosurgery, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Jiefang Avenue 1095 Wuhan, 430030 China

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Tables

Table 1 Surgical treatments and outcomes of 91 pediatric cases with intracranial arachnoid cysts

Table 2 Patients with IACs undergoing cyst resection or fenestration as an initial treatment

Table 3 The reason for surgeries and evaluation of outcomes of the initial treatment

EP epilepsy, NC no change, SDFC subdural fluid collection, HDC hydrocephalus, SDS shunt dependency syndrome, N.N.S. no new symptoms

Table 4 15 operated patients after the initial conservative therapy

L.T. left temporal region, R.T. right temporal region, HDC hydrocephalus

SDS shunt dependency syndrome, m.c.r. microsurgical cyst resection

e.c.f. endoscopic cyst fenestration

#: symptoms relieved or reduction of cyst by more than 50%

*: symptoms relieved and disappeared cysts