Follow-up of pineal cysts in children: is it necessary?
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Pineal cysts are common incidental findings in children undergoing magnetic resonance imaging (MRI). Several studies have suggested MRI follow-up if the cyst is larger than 10 mm. However, cysts do not usually change during follow-up. Prevalence, growth, and structure of the pineal cysts were analyzed to decide if follow-up MRI is necessary.
A retrospective review between 2010 and 2015 was performed using 3851 MRI examinations of children aged 0–16 years to detect pineal cysts having a maximum diameter ≥ 10 mm. Eighty-one children with pineal cysts were identified and 79 of them had been controlled by MRI. Cysts were analyzed for the size, growth, and structure.
A total of 1.8% of the children had a pineal cyst with a diameter ≥ 10 mm. Cysts were present in 48 girls (59.3%) and 33 boys (40.7%). Most pineal cysts (70/79) did not significantly grow during the follow-up (median 10 months, range 3–145 months). A total of 11.4% (9/79) of the cysts grew with the biggest change measured from the outer cyst wall sagittal anteroposterior dimension (mean 3.4 mm ± 1.7 mm). Only one cyst grew more than 5 mm. We found no factors correlating with the cyst growth among 9 cysts that grew > 2 mm.
A majority of pineal cysts remained unchanged during the MRI follow-up. Results of this study suggest that routine MRI follow-up of pineal cysts is not necessary in the absence of unusual radiological characteristics or related clinical symptoms.
KeywordsPineal cyst Brain MRI Children Incidental findings Follow-up
Pineal cyst is a common incidental finding in brain magnetic resonance imaging (MRI) both in children and adults [1, 2, 3, 4, 5]. The prevalence in children and young adults reported in the literature varies widely, ranging from 0.6 to 57% depending on the strength of the magnetic field, slice thickness, and threshold of the size of the cysts included in the studies [1, 5, 6, 7, 8, 9]. However, no adequate autopsy data are available for children . With increasing availability of MRI, more incidental pineal cysts are being detected . High-resolution 3D-imaging and 3 Tesla (T) MRI increase the frequency of detection of the cysts but also improve morphological analysis of their structure [5, 6, 10, 11].
Pineal cysts are usually asymptomatic, but some nonspecific symptoms like headache, vertigo, and nausea have been reported [1, 2, 3, 4, 5, 8]. In rare cases, pineal cysts have caused severe symptoms related to the mass effect of a large cyst compressing the tectum (Parinaud’s syndrome) or hydrocephalus due to stenosis of aqueductus Sylvii [3, 5, 12]. Although classic pineal cysts are benign [5, 13], some cysts can show features overlapping those of cystic neoplastic lesions such as pineocytoma, pineoblastoma, and astrocytoma [14, 15]. The pineal cysts of children with hereditary retinoblastoma should be analyzed carefully, since these patients have an increased risk of developing pineoblastoma [16, 17, 18].
Many previous studies have suggested serial MRI for patients with pineal cysts especially when the greatest diameter exceeds 1 cm [5, 9, 12, 19, 20]. Although some cysts enlarge and others involute during the years of follow-up, most of them remain unchanged [1, 2, 13, 20, 21]. The purpose of this study was to define criteria for choosing pediatric patients with pineal cysts who need follow-up MRI. This study focuses on the size of the pineal cysts and their growth tendency on MRI follow-up. In addition, the wall structure and contrast enhancement of the cysts are reported.
Zero- to sixteen-year-old children with pineal cyst, who had undergone brain MRI at Oulu University Hospital during the period 2010 through 2015, were included in this study. Radiological data was collected from the database of the Department of Radiology. Only patients with pineal cysts with a diameter ≥ 10 mm in at least one imaging plane (axial, sagittal anteroposterior, sagittal perpendicular to tectum) were included in this study. The study was approved by the ethics committee of Oulu University Hospital.
MR scans had been done with either a Magnetom Espree 1.5 T (Siemens, Erlangen, Germany) or a Signa HDx 1.5 T (GE Healthcare, Milwaukee, WI, USA) scanner. All MRI studies included at least the following pulse sequences: axial spin-echo (SE) T2-weighted (TR/TE 4000/112 ms, FOV 230 × 230 mm, matrix 328 × 328, and slice thickness 5 mm with 1.5 mm gap) and axial SE fluid-attenuated inversion recovery (FLAIR, TR/TE/ 8500/112 ms, FOV 230 × 230 mm, matrix 328 × 328, and slice thickness 5 mm with 1.5 mm gap) images of the whole brain. The pineal gland was imaged by turbo spin-echo (TSE) T2-weighted coronal (TR/TE 3500/80 ms, FOV 230 × 230 mm, matrix 170 × 170, and slice thickness 2 mm with 0.2 mm gap), and TSE T1-weighted sagittal and coronal or axial (TR/TE 550/11 ms, FOV 190 × 190 mm, matrix 256 × 192, and slice thickness 2 mm with 0.2 mm gap) sequences without and with gadolinium contrast enhancement (Gadoteric acid, Dotarem®, 0.2 ml/kg, Guerbet, France). Susceptibility-weighted imaging (SWI, TR/TE 49/40 ms, FOV 230 × 230 mm, matrix 384/320, and slice thickness 3 mm) or T2* imaging (TR/TE 800/26 ms, FOV 230 × 230 mm, matrix 280/320 mm, and slice thickness 5 mm with 1.5 mm gap) was performed for 19 patients. MRI scans were evaluated on a research PACS/DICOM viewing application for diagnostic radiology (Neaview, Neagen, Helsinki, Finland).
For the statistical analysis, we divided cysts according to the shape (round or oval), wall thickness (< or ≥ 2 mm), presence of nodularity, internal septations (uni- or multilocular), contrast enhancement, and internal signal relative to that of cerebrospinal fluid (CSF). The initial and follow-up exams were analyzed for the differences in size and structure.
If there were more than two MRI scans performed in a patient, the first and last brain MRI were analyzed. The interval of the follow-up was calculated from the time between the initial and last MRI dates. According to previous studies [2, 22], differences in MRI technique, including patient positioning and slice selection as well as subtle motion artifacts, have been found to cause up to a 2-mm margin error between the studies. Thus, the criterion for the growth of the cyst was considered to be > 2 mm in at least one imaging plane.
All data was analyzed using IBM SPSS statistic 24.0 software (SPSS, Inc.). Numerical data is given for the cases where the cyst increased in size > 2 mm. When comparing changes in cyst size between male and female patients, the unpaired t test was used. A linear regression model was used for comparing the correlation of different factors to cyst size using the r square coefficient (r2). Because the follow-up interval was not normally distributed, the Mann-Whitney U test was used to compare differences in the follow-up interval between the two groups (group 1: no change in the size of the cyst/group 2: cyst size increased > 2 mm). The ANOVA test was used when comparing both mean sizes of cyst in initial MRI and mean ages of patients in two groups (group 1: no change in the size of the cyst/group 2: cyst size increased > 2 mm). For all tests, a significance level of ≤ 0.05 was used. Descriptive values were given as mean ± standard deviation (SD) if not otherwise specified.
A total of 3851 brain MRI examinations from children aged 0–16 years imaged by 1.5 T scanner between the years 2010–2015 were reviewed. Seventy-one patients with a pineal cyst ≥ 10 mm in maximum dimension (prevalence, 1.8%) were found. Ten cases of pineal cysts found before year 2010 were included in the study. Thus, a total of 81 children with pineal cysts ≥ 10 mm were analyzed. The mean age at this incidental finding was 8.6 ± 4.6 years (range 1–16 years). Thirty-three were boys (40.7%) and 48 girls (59.3%).
The most common indication for imaging was headache, which was reported in 44.4% of the children. A total of 14.8% of the patients had seizures. The other indications were migraine (6.2%), developmental delay (6.2%), visual disturbances (6.2%), and vertigo (6.2%). In all these cases, the pineal cysts were considered to be incidental finding unrelated to the presenting symptoms by clinicians.
Six different diameters of the pineal cysts were measured between the outer and inner walls (Fig. 1). The outer and inner mean linear diameters were 12.8 ± 3.0 and 10.1 ± 3.0 mm in the sagittal anteroposterior dimension, 8.9 ± 2.2 and 6.8 ± 2.2 mm in the oblique diameter perpendicular to the tectum, and 10.5 ± 2.3 and 8.0 ± 2.3 mm in the axial width. The size of the cysts did not correlate with the sex of the patients. The mean thickness of the wall was 1.4 ± 0.3 mm. In three cysts, the wall thickness exceeded 2 mm.
Pineal cyst characteristics
T1-weighted intensity relative to CSF
Isointense or slightly hyperintense
T2-weighted intensity relative to CSF on T2-weighted SE sequence
Isointense or slightly hyperintense
T2-weighted intensity relative to CSF on FLAIR-weighted sequence
Isointense or slightly hyperintense
Thin (≤ 2 mm)
Posterior enhancing portion
Seventy-nine of the 81 patients had undergone at least one follow-up brain MR imaging either due to the pineal cyst or for some other reason. The follow-up interval varied from 3 to 145 months with the median interval being 10 months (interquartile range IQR = 19). None of the included patients developed neoplasms.
When the 2-mm error marginal was not taken into account in the measurements of the cysts on the follow-up imaging, the mean change in cyst size varied only from 0.14 to 0.33 mm in all three dimensions measured between inner and outer walls. Signal intensity or wall thickness did not change significantly in any of the 79 cysts on the follow-up MRI. Contrast-enhanced T1W sequences were controlled for 49 patients with the median follow-up interval being 11 months (IQR 14 months, range 3–79 months). The enhancement did not change in any of the pineal cysts during the follow-up period.
Description of the findings of the first MRI for pineal cysts that grew in follow-up ≥ 2 mm at least in one imaging plane
Follow-up interval (months)
Homogenous cyst contents
Wall thickness (mm)
The median follow-up interval of the 9 children with the growth of the pineal cyst > 2 mm was 45 months (interquartile range IQR = 90), whereas in the 70 children whose cysts did not grow significantly, the follow-up period was 8.5 months (interquartile range IQR = 15).
Pineal cysts are considered to be non-neoplastic glial cysts formed within the pineal body. An increasing number of pineal cysts are detected by modern imaging technology. We reviewed data of children who had undergone brain MRI during the years 2010–2015 for pineal cysts ≥ 10 mm in maximal diameter. This cyst size was chosen because follow-up MRI of pineal cysts larger than 10 mm has been recommended in many previous reports [5, 9, 12, 19, 20]. In our study, the prevalence of pineal cysts ≥ 10 mm was 1.8%. We found a higher prevalence of pineal cysts in girls (59.3%) than in boys (40.7%), which is in accordance with the previous studies in children and adults [4, 12, 20, 21]. In this study, there was no statistically significant difference in the prevalence of pineal cysts between children of different ages. However, we did not discover pineal cysts ≥ 10 mm in children under 1 year of age. In a previous retrospective study of children and young adults up to 25 years of age, the prevalence of pineal cysts was reported to be lowest in children under 1 year of age and highest in the age group of 6–12 years in girls and 13–17 years in boys, suggesting an increased prevalence of pineal cysts with increasing age during childhood . However, the threshold of the size of the cysts included in that study was 5 mm, which may explain the difference of the results compared to our data.
Two follow-up studies have indicated that there is no imaging finding that would predict the change or growth of the pineal cysts in children and young adults [2, 22]. In agreement with Al-Holou et al. , gender was not found in this study to correlate with the growth of the pineal cysts. Our data demonstrated that the children whose cysts grew were younger than the children whose cysts remained stable. Similarly, age has been suggested to be related to the change of the size of pineal cysts in the study by Al-Holou et al. .
We studied three plane dimensions of the pineal cysts measured both from the inner and outer walls. Thus, six different values of the cyst size were calculated. In several cysts, the greatest outer diameter was just above 10 mm and the inner diameter just below 10 mm. In our institution, the pineal cysts had been controlled by MRI if the outer diameter was larger than 10 mm. While the limit for follow-up MRI of pineal cysts is recommended in general practice to be ≥ 10 mm, most of the reports concerning pineal cyst size do not specify whether the diameters have been measured from the inner or outer walls [2, 8]. In addition to anteroposterior and axial width, we measured the dimension perpendicular to the tectum to detect whether the cysts cause compression of Aqueductus Sylvii or hydrocephalus. One prior study showed that all patients with obstructive hydrocephalus had cysts greater than 2 cm in diameter  whereas other studies have demonstrated pineal cysts over 2 cm without hydrocephalus [2, 20]. Hydrocephalus or ventricular enlargement with pineal cysts was not found in this study, which is in agreement with the results of Mandera et al. . However, our study population included only three cysts with a diameter over 2 cm.
Pineal cysts usually do not cause any clinical symptoms even though broad range of symptoms has been described [1, 2, 3, 11, 21, 24]. A few rare cases have been reported where pineal cysts may have caused a sudden death from intracystic hemorrhage, apoplexia, or acute hydrocephalus [3, 25]. Seifert et al. reported that headache, especially migraine, has occurred more often in patients with pineal cysts than in a control group . Asymptomatic cysts are considered to be often smaller than 10 mm in diameter [1, 3]. However, most pineal cysts are not considered to need surgery, because cysts rarely grow or cause any symptoms, and any worsening of clinical symptoms is not predictive of an increase in pineal cyst size or change in imaging appearance [2, 21].
Our analysis revealed that pineal cysts do not grow significantly in children, since 89% of the pineal cysts did not increase in any diameter during the follow-up period. Similar results have been demonstrated in previous reports by showing that the cysts remained stable during the follow-up in 71–92% of the cases [2, 5]. We show that only 9 pineal cysts increased in size, the mean value ranging from 2.6 to 3.4 mm in at least one imaging plane. This is in agreement with the report of Whitehead et al., who demonstrated a change of cyst size of from 0.5 to 3.5 mm . Barboriak et al.  showed that only small changes in the size of pineal cysts are frequently seen on MRI. Our data support the findings of this study. We defined the stability of the pineal cyst size as a change in the diameters of 2 mm or less, and there was no significant factor that correlated with cyst growth among those 9 cysts that had grown > 2 mm. These results suggest that cysts do not exhibit marked growth and the radiologic changes are usually clinically insignificant. However, pineal cyst growth during the first decades of life is not considered to be unusual, and the cysts reach a period of quiescence in adulthood before they involute .
It is very challenging to differentiate cystic pineal neoplasm from simple pineal cyst based only on follow-up MRI and clinical interpretation. Both pineocytomas and other pineal region tumors including germ cell tumors, cystic gliomas, as well as dermoid and epidermoid tumors may be cystic [27, 28]. Pineocytomas usually have either internal or nodular wall enhancement on immediate postcontrast imaging and have been misdiagnosed as pineal cysts [19, 29]. There are some radiographic features that may help to distinguish pineal cysts from neoplastic tumors of the pineal region. A typical non-neoplastic pineal cyst is a unilocular fluid-filled mass within the pineal gland . Our analysis revealed 93.8% of the pineal cysts to be isointense or slightly hyperintense compared with CSF on T1W and T2W images, which is a characteristic finding of pineal cysts on MRI [2, 11, 27]. The signal intensity of the cysts is dependent on the protein content and therefore varies from isointense to hyperintense compared to CSF . Enhancement of the cyst walls has been reported in 60% of the cases of pineal cysts to be confined to the rim and thinner than 2 mm [20, 29]. We showed contrast enhancement of the walls of the pineal cysts in 87.8% of the cases on MRI, which is in agreement with the previous results in children . There was no nodular enhancement in this study population. Enhancement of the pineal cysts may resemble solid tumors, which is thought to be due to gadolinium diffusing into the cyst over time . The pineal gland and the wall of the pineal cyst usually demonstrate at least partial enhancement because the pineal gland lacks the blood-brain barrier . In the literature, histologically proven pineal cysts have shown abnormal irregular nodular enhancement , and atypical cysts are frequently detected as an incidental finding in children and are not suggested to be a sign of malignancy . Cauley et al.  reported no significant changes in atypical cystic pineal lesions during MRI follow-up ranging from 7 months to 8 years in children and adults. We show that 18.9% of the cysts had a posterior enhancing portion, which is in agreement with a previous study, where 17% of the cysts demonstrated an enhancing portion posteriorly . In our data, the anterior part of the cyst wall was thicker and enhanced by gadolinium in three children. This posterior or anterior enhancing part of the pineal cyst is suggested to be due either to the presence of pineal tissue  or venous structures . In this study, one cyst showed calcification on MRI and computed tomography (CT), which is a common feature for many cystic pediatric pineal tumors . However, this cyst did not grow or change during a 5-year MRI follow-up. Evidence of hemorrhage on MRI may be associated with symptoms  but not all hemorrhagic pineal cysts present with symptoms . In addition, hemorrhage into the cyst may cause nodular enhancement suggesting a tumor . The protocol of the initial MRI of 9 children and follow-up MRI of 19 children with pineal cysts included susceptibility-weighted imaging (SWI) or T2* images for visualizing the changes in magnetic susceptibility caused by hemorrhage or calcium. However, our data did not show any hemorrhagic pineal cysts.
Follow-up MRI is conducted to confirm stability of the size and structure of pineal cysts in children [2, 3, 5, 8, 12, 20, 22, 24, 34]. Mandera et al. recommended  follow-up of pineal cysts for several years in asymptomatic patients, but their study population was only 24 children. Only two of these cystic pineal lesions were confirmed to be pineocytomas; the rest of them were pineal cysts which did not grow on follow-up . Al-Holou et al. [2, 21] did not suggest radiological or clinical follow-up necessarily in adult patients with asymptomatic pineal cysts. However, they suggested that pineal cysts in children should be followed by MRI whether or not they have symptoms . In that study, younger age at diagnosis was statistically associated with a radiologic change during follow-up, even though the majority of the pineal cysts did not change on serial MRI. In addition, when the cysts changed or grew, they remained asymptomatic . According to Whitehead et al. , imaging follow-up of children is not required if there are no referable symptoms or large cysts which could compress the tectum and cause hydrocephalus. Barboriak et al.  reported that incidental pineal cysts may be followed up on a clinical basis only. Pastel et al.  suggested that the probability of an underlying pineocytoma would not justify the disadvantages that follow-up imaging cause, unless there are new or worsening symptoms. According to Osborn and Preece , both non-neoplastic pineal cysts and typical pineocytoma grow extremely slowly, and follow-up MRI is usually not helpful in differential diagnosis. However, the pineal lesions including cysts of the children with hereditary retinoblastoma should be adequately followed up by MRI because they are at increasing risk of developing pineoblastoma [16, 17, 18]. MRI follow-up is necessary when the imaging appearance of pineal cysts overlaps with the appearance of pineal neoplasms including nodular enhancement, hemorrhage, or large size compressing the tectum or aqueductus Sylvii [33, 34]. Any symptomatic pineal lesion requires definitive diagnosis . MR-guided stereotactic biopsy and tumor markers may be needed for the evaluation and management of the symptomatic patients . In our study, the median time of follow-up was 10 months, ranging from 3 to 145 months. The size of the cysts did not change during the longer follow-up time compared to the shorter one, suggesting that the cysts may not exhibit enlargement even if they would be followed longer. This confirms the results of a previous study, which showed that increasing the interval between follow-up scans may not increase the likelihood of detecting enlargement of the pineal cysts .
When assessing the results of the present and several previous studies [2, 5, 6, 10, 13], pineal cyst follow-up in children appears to be unnecessary, unless there is worsening of symptoms. The threshold of 10 mm is an arbitrary limit for controlling, because there is no evidence that larger cysts are more likely to enlarge [2, 5, 8, 20, 22]. Unnecessary repeated control examinations of children with pineal cysts increase the costs of healthcare. Children under school age usually require anesthesia when imaging, which is always a risk to the patient . Anesthesia increases the imaging time and demands for additional personnel. In addition, the contrast agents can cause adverse effects to the patients . Follow-up scans also cause a huge psychological burden to parents . Reducing unnecessary pineal cyst follow-up scans would release MRI resources to those patients who really need them. It would also reduce the burden on the patients and families as well as decrease costs.
The aim of this study was to find out if we can decrease the amount of unjustified routine follow-up imaging of incidental pineal cysts in children with no suspicion of neoplasm. Gender, cyst size, and shape did not predict growth of the cyst in the follow-up. The follow-up time did not correlate with the changes in cyst sizes in any dimension. Because the probability of underlying cystic neoplasm and the growth tendency of pineal cysts is so small, MRI follow-up is not helpful. Based on these results, we suggest that systematic follow-up of pineal cysts by serial MRI is not indicated in the absence of unusual radiological characteristics or related clinical symptoms.
Compliance with ethical standards
No funding was received for this study.
Conflict of interest
The authors declare that they have no conflict of interest.
All procedures performed in the studies involving human participants were in accordance with the ethical standards of Oulu University Hospital and/or national research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards. For this type of study formal consent is not required.
Informed consent was obtained from all individual participants included in the study.
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