Brainstem tumors: where are we today?

Safety and Technical Efficacy of Pediatric Brainstem Biopsies: An Updated Meta-Analysis of 1000+ Children

BACKGROUND

Brainstem tumors represent ∼10% of pediatric brain tumors, ∼80% of these are diffuse midline glioma. Given invariably poor prognosis in diffuse midline glioma, there continues to be immense variation worldwide in performing biopsy of these lesions. Several contemporary studies in recent years have provided new data to elucidate the safety profile of biopsy and an updated meta-analysis is thus indicated.

METHODS

We found 29 studies of pediatric brainstem biopsy in the last 20 years (2003-2023, 1002 children). We applied meta-analysis of proportions using a random-effects model to generate point estimates, confidence intervals, and measures of heterogeneity.

RESULTS

Eighty-seven percent of procedures were stereotactic needle biopsies (of these, 62% with a frame, 14% without frame, and 24% robotic.) Biopsy resulted in a histological diagnosis ("technical yield") in 96.8% of cases (95% CI 95.4-98.2). Temporary complications were seen in 6% (95 CI 4-8), with the most common neurological complications being 1) cranial nerve dysfunction, 2) worsening or new ataxia, and 3) limb weakness. Permanent complications (excluding death) were seen in 1% (95% CI 0.5-2), most commonly including cranial nerve dysfunction and limb weakness. Five deaths were reported in the entire pooled cohort of 1002 children (0.5%).

CONCLUSIONS

When counseling families on the merits of brainstem biopsy in children, it is reasonable to state that permanent morbidity is rare (<2%). If biopsy is performed specifically to facilitate enrollment in clinical trials requiring a molecular diagnosis, the risks of biopsy outlined here should be weighed against potential benefits of trial enrollment.

Pediatric Brainstem Tumor Biopsy: Surgical Planning and Execution for Maximal Safety and Tissue Yield

Brainstem tumors account for 10-20% of pediatric brain tumors with a peak age of diagnosis between 7 and 9 years old and are often fatal. Historically, diagnosis of brainstem tumors has been largely based on imaging; however, recent studies have demonstrated the incongruities between preoperative MRI diagnosis and postoperative pathological findings highlighting the importance of brainstem biopsy for diagnostic accuracy. Stereotactic brainstem biopsy for pediatric brainstem tumors has been proven to be safe with a high diagnostic yield (96.1-97.4%) and relatively low morbidity and mortality. Successful pediatric brainstem tumor biopsy demands intricate knowledge of brainstem anatomy, cranial nerves and vasculature, and common pediatric brainstem tumors by the performing surgeon. Additionally, understanding of the surgical indications and techniques (e.g., frame-based versus frameless, robotic assistance, surgical approach, and targets selection) helps to ensure maximal safety and tissue yield. Pediatric brainstem biopsy permits histological conformation of brainstem lesions leading to accurate diagnosis and the potential for personalized treatment and future therapeutic research.

Classification of Brainstem Gliomas Based on Tumor Microenvironment Status

The inter-tumor heterogeneity of the tumor microenvironment (TME) and how it correlates with clinical profiles and biological characteristics in brainstem gliomas (BSGs) remain unknown, dampening the development of novel therapeutics against BSGs. The TME status was determined with a list of pan-cancer conserved gene expression signatures using a single-sample gene set enrichment analysis (ssGSEA) and was subsequently clustered via consensus clustering. BSGs exhibited a high inter-tumor TME heterogeneity and were classified into four clusters: "immune-enriched, fibrotic", "immune-enriched, non-fibrotic", "fibrotic", and "depleted". The "fibrotic" cluster had a higher proportion of diffuse intrinsic pontine gliomas (p = 0.041), and "PA-like" tumors were more likely to be "immune-enriched, fibrotic" (p = 0.044). The four TME clusters exhibited distinct overall survival (p < 0.001) and independently impacted BSG outcomes. A four-gene panel as well as a radiomics approach were constructed to identify the TME clusters and achieved high accuracy for determining the classification. Together, BSGs exhibited high inter-tumor heterogeneity in the TME and were classified into four clusters with distinct clinical outcomes and tumor biological properties. The TME classification was accurately identified using a four-gene panel that can potentially be examined with the immunohistochemical method and a non-invasive radiomics method, facilitating its clinical application.

Primary midbrain germinomas: Report of a rare case with an updated review of the literature

Intracranial germinomas are most commonly extra-axial germ cell tumors that are predominantly found in the pineal and suprasellar regions. Primary intra-axial midbrain germinomas are extremely rare, with only eight reported cases. Here we present a 30-year-old man who presented with severe neurological deficits, with an MRI that showed a heterogeneously enhancing mass with ill-defined margins in the midbrain, and with surrounding vasogenic edema extending to the thalamus. The presumptive preoperative differential diagnosis included glial tumors and lymphoma. The patient underwent a right paramedian suboccipital craniotomy and biopsy obtained through the supracerebellar infratentorial transcollicular approach. The histopathological diagnosis was reported as pure germinoma. After patient discharge, he received chemotherapy with carboplatin and etoposide, followed by radiotherapy. Follow-up MRI at up to 26 months showed no contrast-enhancing lesions but a mild T2 FLAIR hyperintensity adjacent to the resection cavity. Differential diagnosis of midbrain lesions can be challenging and should include glial tumors, primary central nervous system lymphoma, germ cell tumors, and metastasis. Accurate diagnosis requires adequate tissue sampling. In this report, we present a very rare case of a primary intra-axial germinoma of the midbrain which is biopsied via a transcollicular approach. This report is also unique as it provides the first surgical video of an open biopsy and the microscopic appearance of an intra-axial primary midbrain germinoma via a transcollicular approach.

Brainstem tumors may increase the impairment of behavioral emotional cognition in children

PURPOSE

It remains unclear as to whether patients with brainstem tumor experience complex neuropsychiatric problems. In this cohort study, we specifically investigated behavioral, emotional and cognitive symptoms in pediatric patients with brainstem glioma and healthy individuals.

METHODS

A total of 146 patients with pediatric brainstem tumors (aged 4-18 years old) and 46 age-matched healthy children were recruited to assess their behaviors and emotions examined by the Child Behavior Checklist. A variety of clinical factors were also analyzed.

RESULTS

There were significant differences in most behavioral and emotional symptoms between pediatric patients and healthy subjects. Moreover, patients with pons tumors exhibited significantly higher scores than patients with medulla oblongata tumors (p = 0.012), particularly in concerning the syndrome categories of Withdrawn (p = 0.043), Anxious/depressed symptoms (p = 0.046), Thought Problems (p = 0.004), Attention deficits (p = 0.008), Externalizing problems (p = 0.013), and Aggressive behavior (p = 0.004). A tumor body located in the pontine (p = 0.01, OR = 4.5, 95% CI = 1.4-14.059) or DIPG in the midbrain (p = 0.002, OR = 3.818, 95% CI = 1.629-8.948) appears to act as a risk factor that is associated with more problems in patients with neuropsychiatric symptoms.

CONCLUSIONS

Pediatric patients with brainstem tumors exhibit severe behavioral and emotional problems. Tumor invades the pontine and midbrain act a risk factor with more problems. It suggests that structural and functional abnormalities in the brainstem will cause prolonged behavioral problems and emotional-cognitive dysfunctions in young children.

5-aminolevulinic acid-guided surgery for focal pediatric brainstem gliomas: A preliminary study

Background:

There is a growing body of literature supporting the use of 5-aminolevulinic acid (5-ALA) in the pediatric population, however, its use is still considered “off label” in this setting. In this retrospective study, we report our experience using 5-ALA in pediatric patients with focal brainstem gliomas (BSGs).

Methods:

Patients younger than 16 years presenting with a newly diagnosed BSG that was focal in nature were considered suitable for treatment with 5-ALA-assisted surgery. Exclusion criteria included MRI features suggestive of a diffuse intrinsic pontine glioma. A single dose of 5-ALA was administered preoperatively. Intraoperative fluorescence was recorded as “solid,” “vague,” or “none.” The effectiveness of the fluorescence was graded as “helpful” or “unhelpful.”

Results:

Eight patients underwent 5-ALA-assisted surgery. There were four tumors located in the pons, two midbrain tumors, and two cervicomedullary tumors. Histological analysis demonstrated three diffuse astrocytomas, three pilocytic astrocytomas, and two anaplastic astrocytomas. Solid fluorescence was found in three of the eight cases, vague fluorescence was found in two cases, and no fluorescence was found in three cases. Fluorescence was useful in 3 (37%) cases. No patients experienced any complications attributable to the administration of the 5-ALA.

Conclusion:

With a total fluorescence rate of 62.5% but a subjectively assessed “usefulness” rate of only 37.5%, the role of 5-ALA in BSG surgery is limited. Given the toxicological safety, however, of the agent, caution is perhaps needed before dismissing the use of 5-ALA entirely.

Safety and efficacy of brainstem biopsy in children and young adults

OBJECTIVE

Biopsies of brainstem lesions are performed to establish a diagnosis in the setting of an atypical clinical or radiological presentation, or to facilitate molecular studies. A better understanding of the safety and diagnostic yield of brainstem biopsies would help guide appropriate patient selection.

METHODS

All patients who underwent biopsy of a brainstem lesion during the period from January 2011 to June 2019 were reviewed. Demographic, radiological, surgical, and outcome data were collected.

RESULTS

A total of 58 patients underwent 65 brainstem biopsies during the study period. Overall, the median age was 7.6 years (IQR 3.9-14.2 years). Twenty-two of the 65 biopsies (34%) were open, 42 (65%) were stereotactic, and 1 was endoscopic. In 3 cases (5%), a ventriculoperitoneal shunt was placed, and in 9 cases (14%), a posterior fossa decompression was performed during the same operative session as the biopsy. An intraoperative MRI (iMRI) was performed in 28 cases (43%). In 3 of these cases (11%), the biopsy was off target and additional samples were obtained during the same procedure. New neurological deficits were noted in 5 cases (8%), including sensory deficits, ophthalmoparesis/nystagmus, facial weakness, and hearing loss; these deficits persisted in 2 cases and were transient in 3 cases. A pseudomeningocele occurred in 1 patient; no patients developed a CSF leak or infection. In 8 cases (13%) an additional procedure was needed to obtain a diagnosis.

CONCLUSIONS

Brainstem biopsies are safe and effective. Target selection and approach should be a collaborative effort. iMRI can be used to assess biopsy accuracy in real time, thereby allowing any adjustment if necessary.

Impact of histological diagnosis on the treatment of atypical brainstem lesions

For atypical brainstem lesions, histological diagnosis can have an impact on treatment, especially in cases where diffuse glioma is not found. Since radiotherapy is the only therapeutic modality that has shown clinical and radiographic improvement in patients with diffuse glioma, the misdiagnosis of diffuse glioma can have drastic consequences, particularly in patients with nontumorous lesions. Thus, the purpose of this study was to evaluate the impact of histological diagnosis on the treatment of atypical brainstem lesions. This was a retrospective study of 31 patients who underwent biopsy of atypical brainstem lesions. The procedures were performed between January 2008 and December 2018 at the Life Center Hospital and Santa Casa de Belo Horizonte, MG, Brazil. A diagnosis was obtained in 26 (83.9%) cases. Three patients presented complications: one presented bleeding with no clinical repercussions and two showed worsening of neurological deficit, only one of which was definitive. No mortality occurred due to the procedure. The histological diagnosis was diffuse glioma in seven cases (22.6%) and not diffuse glioma in 19 cases (61.3%). Thus, the histological diagnosis had an impact on the treatment of 19 patients (treatment impact rate: 61.3%). The histological diagnosis of intrinsic brainstem lesions is a safe, efficient procedure with a high diagnosis rate, and as such, it should be considered in the management of atypical lesions.

Pediatric diffuse intrinsic pontine glioma: where do we stand?

Pediatric diffuse intrinsic pontine glioma (DIPG) represents approximately 20% of all pediatric CNS tumors. However, disease outcomes are dismal with a median survival of less than 1 year and a 2-year overall survival rate of less than 10%. Despite extensive efforts to improve survival outcomes, progress towards clinical improvement has been largely stagnant throughout the last 4 decades. Focal radiotherapy remains the standard of care with no promising single-agent alternatives and no evidence for improvement with the addition of a long list of systemic therapies. A better understanding of the biology of DIPG, though not easy due to obstacles in obtaining pathological material to study, is promising for the development of specific individualized treatment for this fatal disease. Recent studies have found epigenetic mutations to be successful predictors and prognostic factors for developing future management policies. The aim of this review is to give a global overview about the epidemiology, diagnosis, and treatment of DIPG. We further examine the controversial biopsy and autopsy issue that is unique to DIPG and assess the subsequent impact this issue has on the research efforts and clinical management of DIPG.

The intersect of neurosurgery with diffuse intrinsic pontine glioma

An invited article highlighting diffuse intrinsic pontine glioma (DIPG) to celebrate the 75th Anniversary of the Journal of Neurosurgery, a journal known to define surgical nuance and enterprise, is paradoxical since DIPG has long been relegated to surgical abandonment. More recently, however, the neurosurgeon is emerging as a critical stakeholder given our role in tissue sampling, collaborative scientific research, and therapeutic drug delivery. The foundation for this revival lies in an expanding reliance on tissue accession for understanding tumor biology, available funding to fuel research, and strides with interventional drug delivery.

Abnormal Neural Activity in Children With Diffuse Intrinsic Pontine Glioma Had Manifested Deficit in Behavioral Inhibition: A Resting-State Functional MRI Study

PURPOSE

The purpose of this study was to investigate whether alterations of regional neural function in children with diffuse intrinsic pontine glioma (DIPG) had manifested deficit in behavioral inhibition using resting-state functional MRI (rs-fMRI).

METHODS

There were 17 participants with DIPG who took part in the study. Eight children were with deficit in behavioral inhibition, whereas the other 9 children did not obtain deficit in behavioral inhibition. Five healthy children with age, sex, and education matched to the study group also participated as the control group. These 3 groups underwent rs-fMRI, and the results were then converted to amplitude of low-frequency fluctuation (ALFF) data. Amplitude of low-frequency fluctuation data were further analyzed by single-factor analysis of variance comparing among 3 groups based on the whole brain levels. Amplitude of low-frequency fluctuation results were subjected to t test of voxel-wised comparison to derive the rs-fMRI brain function differences between the 2 DIPG groups. The Pearson correlation between ALFF values of abnormal regions found in 3 groups and the scores obtained according to the Child Behavior Checklist were analyzed.

RESULTS

The 3 groups had shown significant differences in terms of the ALFF results, with the ALFF increased in several brain regions (P < 0.05, corrected with AlphaSim, clusters >59 voxels), which include left supramarginal gyrus, left dorsolateral superior frontal gyrus, right precentral gyrus, and right middle frontal gyrus. Participants with deficit in behavioral inhibition had shown significant differences (ALFF decreased) in several brain regions, including left dorsolateral superior frontal gyrus and right fusiform gyrus (P < 0.05, corrected with AlphaSim, clusters >123 voxels), whereas other brain regions had shown ALFF increased, including left supramarginal gyrus, left middle frontal gyrus, and right medial superior frontal gyrus (P < 0.05, corrected with AlphaSim, clusters >123 voxels). There was no significant correlation between ALFF values and Child Behavior Checklist scores (P > 0.05).

CONCLUSIONS

These findings of focal spontaneous hyperfunction and hypofunction, which correlate with deficit in behavioral inhibition processing, and the abnormal brain regions are considered to be inefficient (in regions of the brain that may relate to compensatory brain and behavioral functioning, and it may be that the brain region needs to exert extra energy to perform a task to the same degree as the control group) or inability (inability in a certain region, or underpowered), pointing to a pathophysiologic process in executive dysfunction.

Successful Surgery of Exophytic Brainstem Glioma Mimicking Cerebellar-Pontine Angle Tumor: Case Report and Review of Literature

BACKGROUND

Nontectal plate exophytic brainstem gliomas with pilocytic histology are rare and occur mainly in children. Because of their eloquent location, therapy usually consists of bioptic histologic verification and radiotherapy in case of progression.

CASE DESCRIPTION

We report on a 43-year-old patient who presented with intermittent tinnitus and reduced hearing in his left ear, as well as a slight left-sided ataxia. Magnetic resonance imaging revealed a left-sided solid cystic cerebellar-pontine angle (CPA) tumor completely obliterating the CPA. Radiologically, a solid cystic vestibular schwannoma was diagnosed. Intraoperatively, a glossy-grayish, intensively bleeding tumor without any capsule or delineation to the brainstem or cranial nerves was resected using electrophysiologic monitoring. Postoperative histology revealed a pilocytic astrocytoma. Three months postoperatively, hearing was preserved (pure tone average-35 dB) and ataxia was equal to what it was preoperatively, gradually becoming better. Postoperative magnetic resonance scans demonstrated a complete resection of the tumor with completely restored brainstem contours.

CONCLUSIONS

Exophytic brainstem gliomas may occur in the CPA and mimic vestibular schwannoma. Complete resection even with preserved hearing without neurologic deterioration may be feasible.

Role of Radiation Therapy in the Management of Diffuse Intrinsic Pontine Glioma: A Systematic Review

Purpose

Diffuse intrinsic pontine glioma (DIPG) is the most aggressive primary pediatric brain tumor, with <10% of children surviving 2 years. Radiation therapy (RT) remains the mainstay of treatment, but there is a great clinical need for improvements and advancements in treatment strategies. The aim of this systematic review was to identify all available studies in which RT was used to treat patients with DIPG.

Methods and Materials

A literature search for studies published up to March 10, 2018 was conducted using the PubMed database. We identified 384 articles using search items “diffuse intrinsic pontine glioma” and 221 articles using search items “diffuse brainstem glioma radiotherapy.” Included studies were prospective and retrospective series that reported outcomes of DIPG treatment with RT.

Results

We identified 49 studies (1286 patients) using upfront conventionally fractionated RT, 5 studies (92 patients) using hypofractionated RT, and 8 studies (348 patients) using hyperfractionated RT. The mean median overall survival (OS) was 12.0 months, 10.2 months, and 7.9 months in patients who received conventional, hyperfractionated, and hypofractionated RT regimens, respectively. Patients undergoing radiosensitizing therapy had a mean median OS of 11.5 months, and patients who did not receive concomitant systemic therapy had an OS of 9.4 months. In patients who received salvage RT, the mean median OS from initial diagnosis was 16.3 months.

Conclusions

As one of the largest systematic reviews examining RT for DIPG, this report may serve as a useful tool to help clinicians choose the most appropriate treatment approach, while also providing a platform for future investigations into the utility of RT and systemic therapy.

Neuronavigation-Guided Corticospinal Tract Mapping in Brainstem Tumor Surgery: Better Preservation of Motor Function

OBJECTIVE

To evaluate a new technique in brainstem surgery, neuronavigation (NN)-guided corticospinal tract (CST) mapping, in a retrospective study of patients undergoing brainstem tumor surgery.

METHODS

We studied 40 patients with a brainstem tumor who were enrolled in this study. Patients whose worst preoperative muscle strength of the 4 limbs was greater than 3 levels from normal on the Lovett scale were divided into 2 groups: a treatment group of 21 patients who underwent NN-guided CST mapping and routine intraoperative neurophysiology monitoring (IONM) and a control group of 19 patients who underwent routine NN and IONM. Preoperative muscle strength and postoperative (day 90 postsurgery) muscle strength were assessed and compared between the 2 groups.

RESULTS

In the NN-guided CST mapping group, 3 patients (14.3%) had a decrease in muscle strength by 1 level postoperatively, and no patient experienced a decrease of >1 level. In the control group, 4 patients (21.1%) had a 1-level decrease in muscle strength, and 5 (26.3%) had a decrease of >1 level. Patients in the NN-guided CST mapping group had significantly better surgical outcomes compared with those in the control group (P = 0.018, Fisher exact test).

CONCLUSIONS

Brainstem tumor resection using NN-guided CST mapping achieved better preservation of motor function compared with routine NN and IONM. NN-guided CST mapping not only decreased the difficulty of the surgery, but also significantly improved the efficiency of surgery.

Update on the diagnostic value and safety of stereotactic biopsy for pediatric brainstem tumors: a systematic review and meta-analysis of 735 cases

OBJECTIVE Recent studies have shed light on the molecular makeup of diffuse intrinsic pontine gliomas and led to the identification of potential treatment targets for these lesions, which account for the majority of pediatric brainstem tumors (pedBSTs). Therefore, stereotactic biopsy-driven molecular characterization of pedBSTs may become an important prerequisite for the management of these fatal brain tumors. The authors conducted a systemic review and meta-analysis to precisely determine the safety and diagnostic success of stereotactic biopsy of pedBSTs. METHODS A systematic search of PubMed, EMBASE, and the Web of Science yielded 944 potentially eligible abstracts. Meta-analysis was conducted on 18 studies (including the authors' own institutional series), describing a total of 735 biopsy procedures for pedBSTs. The primary outcome measures were diagnostic success and procedure-related complications. Pooled estimates were calculated based on the Freeman-Tukey double-arcsine transformation and DerSimonian-Laird random-effects model. Heterogeneity, sensitivity, and meta-regression analyses were also conducted. RESULTS The weighted average proportions across the analyzed studies were 96.1% (95% CI 93.5%-98.1%) for diagnostic success, 6.7% (95% CI 4.2%-9.6%) for overall morbidity, 0.6% (95% CI 0.2%-1.4%) for permanent morbidity, and 0.6% (95% CI 0.2%-1.3%) for mortality. Subgroup analyses at the study level identified no significant correlation between the outcome measures and the distribution of the chosen biopsy trajectories (transfrontal vs transcerebellar), age, year of publication, or the number of biopsy procedures annually performed in each center. CONCLUSION Stereotactic biopsy of pedBSTs is safe and allows successful tissue sampling as a prerequisite for the molecular characterization and the identification of potentially druggable targets toward more individualized treatment concepts to improve the outcome for children harboring such lesions.

Potential New Therapies for Pediatric Diffuse Intrinsic Pontine Glioma

Diffuse intrinsic pontine glioma (DIPG) is an extensively invasive malignancy with infiltration into other regions of the brainstem. Although large numbers of specific targeted therapies have been tested, no significant progress has been made in treating these high-grade gliomas. Therefore, the identification of new therapeutic approaches is of great importance for the development of more effective treatments. This article reviews the conventional therapies and new potential therapeutic approaches for DIPG, including epigenetic therapy, immunotherapy, and the combination of stem cells with nanoparticle delivery systems.

Cognitive outcomes among survivors of focal low-grade brainstem tumors diagnosed in childhood

Pediatric focal low-grade brainstem tumors are associated with excellent prognosis. Surgical resection and conformal radiation therapy are front-line treatment options; radiation therapy (RT) serves as an excellent treatment for disease progression. Given high survival rates and limited research regarding functional outcomes, the current study examined neurocognitive outcomes in a group of low-grade brainstem glioma survivors. Forty-three survivors of focal low-grade brainstem gliomas underwent neurocognitive assessment (58 % male; median = 6.9 years at diagnosis; median = 14.9 years at latest assessment). Treatment included combinations of surgery, chemotherapy, and RT with 70 % ultimately receiving RT. Neurocognitive outcomes were evaluated through retrospective chart review. Intellectual and academic performance were significantly different from normative expectations (full scale IQ = 86.5 ± 16.8; reading comprehension = 91.3 ± 16.4; math reasoning = 88.2 ± 18.9; reference group = 100 ± 15). Further, the percentage performing below average exceeded the expected 16 % in the normative sample (full scale IQ = 43 %; reading comprehension = 37 %; math reasoning = 50 %). Mean parent ratings did not reflect concerns regarding internalizing and externalizing behaviors or executive functioning (internalizing = 54.9 ± 12.7; externalizing = 51.6 ± 14.6, global executive composite = 57.1 ± 16.0; reference group = 50 ± 10); however, the proportion with clinically elevated scores was higher than the expected 16 % (internalizing = 42 %; externalizing = 26 %; global executive composite = 38 %). Mean performance fell below average for visual-motor coordination (81.8 ± 13.2) and parent ratings of adaptive functioning (73.4 ± 24.2), with 65 and 62 % falling outside the average range, respectively. There were no significant differences between those receiving and not receiving RT. Multiple cognitive domains were significantly different from normative expectations. Despite focal disease and treatment targeting subcortical brain regions, neurocognitive risks exist that may impact treatment planning and caregiver education.

Analysis of survival in pediatric high-grade brainstem gliomas: A population-based study

Background:

The purpose of this study was to use the National Cancer Institutes’ Surveillance, Epidemiology, and End Results (SEER) database to perform a large-scale analysis of brainstem anaplastic astrocytoma (AA) and glioblastoma multiforme (GBM). Use of the SEER database gave us a larger sample size of this rare tumor type, allowing for the analysis of the relationship between prognostic factors and survival.

Materials and Methods:

We selected pediatric patients (<18 years old) from the SEER database with histologically confirmed diagnoses of primary high-grade gliomas (World Health Organization Grade III/IV) of the brainstem. In univariate and multivariate analysis, we analyzed the relationship between demographic (age, gender, race, diagnosis date), histologic (AA, GBM), and treatment (surgery, radiation) factors on survival.

Results:

In our cohort of 124 patients, those with AA had a median survival of 13 months and those with GBM 9 months. Higher-grade tumors were associated with statistically significantly increased mortality (hazard ratio [HR]: 1.74, confidence intervals [CIs]: 1.17-2.60). Surgical intervention was associated with a significantly lower mortality, either alone (HR: 0.14, CI: 0.04-0.5) or in combination with radiation (HR: 0.35, CI: 0.15-0.82). Radiation therapy alone was significantly associated with decreased mortality within the first 9 months after diagnosis but not with overall mortality. No demographic characteristics were significantly associated with mortality.

Conclusions:

Outcome remains poor in the pediatric high-grade brainstem glioma population. Survival is correlated with lower-grade tumor histology, radiation therapy only in the first 9 months after diagnosis, and surgical resection.

DIPG in Children - What Can We Learn from the Past?

Brainstem tumors represent 10–15% of pediatric central nervous system tumors and diffuse intrinsic pontine glioma (DIPG) is the most common brainstem tumor of childhood. DIPG is almost uniformly fatal and is the leading cause of brain tumor-related death in children. To date, radiation therapy (RT) is the only form of treatment that offers a transient benefit in DIPG. Chemotherapeutic strategies including multi-agent neoadjuvant chemotherapy, concurrent chemotherapy with RT, and adjuvant chemotherapy have not provided any survival advantage. To overcome the restrictive ability of the intact blood–brain barrier (BBB) in DIPG, several alternative drug delivery strategies have been proposed but have met with minimal success. Targeted therapies either alone or in combination with RT have also not improved survival. Five decades of unsuccessful therapies coupled with recent advances in the genetics and biology of DIPG have taught us several important lessons (1). DIPG is a heterogeneous group of tumors that are biologically distinct from other pediatric and adult high grade gliomas (HGG). Adapting chemotherapy and targeted therapies that are used in pediatric or adult HGG for the treatment of DIPG should be abandoned (2). Biopsy of DIPG is relatively safe and informative and should be considered in the context of multicenter clinical trials (3). DIPG probably represents a whole brain disease so regular neuraxis imaging is important at diagnosis and during therapy (4). BBB permeability is of major concern in DIPG and overcoming this barrier may ensure that drugs reach the tumor (5). Recent development of DIPG tumor models should help us accurately identify and validate therapeutic targets and small molecule inhibitors in the treatment of this deadly tumor.

Cervicomedullary tumors in children

OBJECT

Cervicomedullary tumors (CMTs) represent a heterogeneous group of intrinsic neoplasms that are typically low grade and generally carry a good prognosis. This single-institution study was undertaken to document the outcomes and current treatment philosophy for these challenging neoplasms.

METHODS

The charts of all pediatric patients with CMTs who received treatment at St. Jude Children's Research Hospital between January 1988 and May 2013 were retrospectively reviewed. Demographic, surgical, clinical, radiological, pathological, and survival data were collected. Treatment-free survival and overall survival were estimated, and predictors of recurrence were analyzed.

RESULTS

Thirty-one children (16 boys, 15 girls) with at least 12 months of follow-up data were identified. The median age at diagnosis was 6 years (range 7 months-17 years) and the median follow-up was 4.3 years. Low-grade tumors (Grade I or II) were present in 26 (84%) patients. Thirty patients underwent either a biopsy alone or resection, with the majority of patients undergoing biopsy only (n = 12, 39%) or subtotal resection (n = 14, 45%). Only 4 patients were treated solely with resection; 21 patients received radiotherapy alone or in combination with other treatments. Recurrent tumor developed in 14 children (45%) and 4 died as a result of their malignancy. A high-grade pathological type was the only independent variable that predicted recurrence. The 5- and 10-year treatment-free survival estimates are 64.7% and 45.3%, respectively. The 5- and 10-year overall survival estimate is 86.7%.

CONCLUSIONS

Children with CMTs typically have low-grade neoplasms and consequently long-term survival, but high risk of recurrence. Therapy should be directed at achieving local tumor control while preserving and even restoring neurological function.

Pediatric brainstem gliomas: new understanding leads to potential new treatments for two very different tumors

Pediatric brainstem gliomas include low-grade focal brainstem gliomas (FBSG) and high-grade diffuse intrinsic pontine gliomas (DIPG). These tumors share a crucial and eloquent area of the brain as their location, which carries common challenges for treatment. Otherwise, though, these two diseases are very different in terms of presentation, biology, treatment, and prognosis. FBSG usually present with greater than 3 months of symptoms, while DIPG are usually diagnosed within 3 months of symptom onset. Surgery remains the preferred initial treatment for FBSG, with chemotherapy used for persistent, recurrent, or inoperable disease; conversely, radiation is the only known effective treatment for DIPG. Recent developments in biological understanding of both tumors have led to new treatment possibilities. In FBSG, two genetic changes related to BRAF characterize the majority of tumors, and key differences in their biological effects are informing strategies for targeted chemotherapy use. In DIPG, widespread histone H3 and ACVR1 mutations have led to new hope for effective targeted treatments. FBSG has an excellent prognosis, while the long-term survival rate of DIPG tragically remains near zero. In this review, we cover the epidemiology, biology, presentation, imaging characteristics, multimodality treatment, and prognosis of FBSG and DIPG, with a focus on recent biological discoveries.

Surgical approaches for brainstem tumors in pediatric patients

PURPOSE

To analyze the pathways to brainstem tumors in childhood, as well as safe entry zones.

METHOD

We conducted a retrospective study of 207 patients less than 18 years old who underwent brainstem tumor resection by the first author (Cavalheiro, S.) at the Neurosurgical Service and Pediatric Oncology Institute of the São Paulo Federal University from 1991 to 2011.

RESULTS

Brainstem tumors corresponded to 9.1 % of all pediatric tumors operated in that same period. Eleven previously described "safe entry zones" were used. We describe a new safe zone located in the superior ventral pons, which we named supratrigeminal approach. The operative mortality seen in the first 2 months after surgery was 1.9 % (four patients), and the morbidity rate was 21.2 %.

CONCLUSIONS

Anatomic knowledge of intrinsic and extrinsic brainstem structures, in association with a refined neurosurgical technique assisted by intraoperative monitoring, and surgical planning based on magnetic resonance imaging (MRI) and tractography have allowed for wide resection of brainstem lesions with low mortality and acceptable morbidity rates.

Neurosurgical treatment of pediatric low-grade midbrain tumors: a single consecutive institutional series of 15 patients

OBJECT

The authors delineate the long-term results of surgical treatment for pediatric low-grade midbrain glioma.

METHODS

A series of 15 consecutive patients (age range 0-15 years) who underwent primary tumor resection for a low-grade midbrain glioma during the years 1989-2010 were included in this retrospective study on surgical morbidity, mortality rate, academic achievement, and/or work participation. Gross motor function and activities of daily living were scored according to the Barthel Index.

RESULTS

Of the 15 patients, 10 were in their 1st decade (age 0-9 years) and 5 were in their 2nd decade of life (age 10-15 years) at the time of surgery. The male/female ratio was 0.50 (5:10). No patients were lost to follow-up. One patient died in the postoperative period (32 days posttreatment). Another 2 patients died during follow-up. One patient succumbed to acute bleeding in the resection cavity 8 months after surgery, and the other died of shunt failure 21 years after initial treatment. Twelve patients are alive at the time of this writing, with follow-up periods from 3 to 24 years (median 8 years). Among the 12 survivors, the Barthel Index scores were normal (100) in 11 patients and 80 in 1 patient. A total of 25 tumor resections were performed. In 1 patient, further resection was performed 5 days after initial resection due to MRI-confirmed residual tumor. Another 5 patients underwent repeat tumor resection after MRI-confirmed progressive tumor disease and clinical deterioration ranging from 3 months to 4 years after the initial operation. Three of these 5 patients also underwent a third resection, and 1 of the 3 underwent a fourth operation. Six children received adjuvant therapy: local radiotherapy in 2 patients, chemotherapy in 3 patients, and both in 1 patient. Twelve (80%) of the 15 patients needed treatment for persistent hydrocephalus.

CONCLUSIONS

Selected cases of low-grade midbrain gliomas may clearly benefit from resection with favorable results, even for prolonged periods. Three patients in the present series died, one of whom had a prolonged survival period of 21 years. Among the 12 survivors, stable long-term results appeared obtainable in at least 9. One patient died of acute hemorrhage 8 months after initial resection; otherwise, rapid tumor progression and death were not observed. Forty percent of the patients received adjuvant treatment, with local radiotherapy, chemotherapy, or both.

Diagnostic value and safety of stereotactic biopsy for brainstem tumors: a systematic review and meta-analysis of 1480 cases

BACKGROUND

The feasibility and safety of stereotactic biopsy for brainstem tumors (BSTs) are controversial. Although magnetic resonance imaging (MRI) has been reported as the preferred diagnostic tool, histopathological analysis is frequently necessary to establish a definitive diagnosis. Recent advances in molecular characterization of brainstem gliomas-accounting for the majority of BSTs-have revealed several potential targets for molecular-based therapies. Hence, a molecular stereotactic biopsy that combines histopathological diagnosis with molecular-genetic analysis will become increasingly important for patients with BSTs.

OBJECTIVE

We conducted a systemic review and meta-analysis to determine the risks and benefits of stereotactic biopsy for BSTs.

METHODS

A systematic search in PubMed, Embase, and the Web of Science yielded 3766 potentially eligible abstracts. Meta-analysis was conducted on 38 studies describing 1480 biopsy procedures for BSTs. Primary outcome measures were diagnostic success and procedure-related complications. Data were analyzed according to standard meta-analytic techniques.

RESULTS

The weighted average proportions across the analyzed studies were: 96.2% (95% confidence interval [CI]: 94.5%-97.6%) for diagnostic success, 7.8% (95% CI: 5.6%-10.2%) for overall morbidity, 1.7% (95% CI: 0.9%-2.7%) for permanent morbidity, and 0.9% (95% CI: 0.5%-1.4%) for mortality. Meta-regression revealed a significant correlation between diagnostic success rates and the number of biopsy procedures performed annually in each center (P = .011). Other factors did not affect the outcome measures.

CONCLUSION

Stereotactic biopsy of BSTs is safe. It allows exact histopathological diagnosis as a prerequisite for adequate treatment and opens new perspectives for the molecular characterization of these tumors as a crucial first step toward more individualized treatment concepts.

ABBREVIATIONS

: BST, brainstem tumorCI, confidence intervalD-BSG, diffuse brainstem gliomaHGG, high-grade gliomaLGG, low-grade gliomasTC, transcerebellarTF, transfrontal.

Differences between brainstem gliomas in juvenile and adult rats

Clinical studies have shown that gliomas of the brainstem behave differently in children and adults. The aim of the present study was to compare and analyze the differences between these gliomas in juvenile and adult rats with regard to tumor growth, survival, pathology and magnetic resonance imaging (MRI). A total of 25 juvenile and 25 adult Wistar rats were divided into groups A (15 juvenile rats), B (10 juvenile rats), C (15 adult rats) and D (10 adult rats). The rats of groups A and C (experimental) were injected with glioma cells, while groups B and D (control) were injected with a physiological saline solution. Rat neurological signs, survival time, tumor size, hematoxylin and eosin (HE) staining and immunohistochemical staining for MMP-2, MMP-9 and β-catenin were compared. The survival time of group A was 19.47±2.232 days, whereas that of group C was 21.47±2.232 days (P<0.05). The tumor sizes were 4.55 and 4.62 mm (P>0.05) in groups A and C, respectively. HE and immunohistochemical staining revealed no differences between the groups. The results suggest that the growth patterns and invasiveness of brainstem gliomas may vary in children compared with adults due to the varied biological behaviors of the tumor cells.

Brainstem oligodendroglioma in a puppy

A 5 mo old male golden retriever presented for evaluation of an acute onset, progressive neurologic disease. Although computed tomography (CT) was unremarkable, MRI identified an ill-defined mass located in the medulla, which was considered likely responsible for the clinical signs. The imaging features closely resembled the classic features of human brainstem gliomas in the pediatric population. Histopathologic examination confirmed the lesion to be an anaplastic oligodendroglioma.

Management and outcome of focal low-grade brainstem tumors in pediatric patients: the St. Jude experience

OBJECT

Whereas diffuse intrinsic pontine gliomas generally have a short symptom duration and more cranial nerve involvement, focal brainstem gliomas are commonly low grade, with fewer cranial neuropathies. Although these phenotypic distinctions are not absolute predictors of outcome, they do demonstrate correlation in most cases. Because there is a limited literature on focal brainstem gliomas in pediatric patients, the objective of this paper was to report the management and outcome of these tumors.

METHODS

The authors reviewed the records of all children diagnosed with radiographically confirmed low-grade focal brainstem gliomas from 1986 to 2010. Each patient underwent biopsy or resection for tissue diagnosis. Event-free survival (EFS) and overall survival were evaluated. Univariate analysis was conducted to identify demographic and treatment variables that may affect EFS.

RESULTS

Fifty-two patients (20 girls, 32 boys) with follow-up data were identified. Median follow-up was 10.0 years, and the median age at diagnosis was 6.5 years (range 1-17 years). The tumor locations were midbrain (n = 22, 42%), pons (n = 15, 29%), and medulla (n = 15, 29%). Surgical extirpation was the primary treatment in 25 patients (48%). The 5- and 10-year EFS and overall survival were 59%/98% and 52%/90%, respectively. An event or treatment failure occurred in 24 patients (46%), including 5 deaths. Median time to treatment failure was 3.4 years. Disease progression in the other 19 patients transpired within 25.1 months of diagnosis. Thirteen of these patients received radiation, including 11 within 2 months of primary treatment failure. Although children with intrinsic tumors had slightly better EFS at 5 years compared with those with exophytic tumors (p = 0.054), this difference was not significant at 10 years (p = 0.147). No other variables were predictive of EFS.

CONCLUSIONS

Surgery suffices in many children with low-grade focal brainstem gliomas. Radiation treatment is often reserved for disease progression but offers comparable disease control following biopsy. In the authors' experience, combining an assessment of clinical course, imaging, and tumor biopsy yields a reasonable model for managing children with focal brainstem tumors.

Characterization of a diffuse intrinsic pontine glioma cell line: implications for future investigations and treatment

Diffuse intrinsic pontine gliomas arise almost exclusively in children, and despite advances in treatment, the majority of patients die within 2 years after initial diagnosis. Because of their infiltrative nature and anatomic location in an eloquent area of the brain, most pontine gliomas are treated without a surgical biopsy. The corresponding lack of tissue samples has resulted in a limited understanding of the underlying genetic and molecular biologic abnormalities associated with pontine gliomas, and is a substantial obstacle for the preclinical testing of targeted therapeutic agents for these tumors. We have established a human glioma cell line that originated from surgical biopsy performed on a patient with a pontine glioma. To insure sustainable in vitro propagation, tumor cells were modified with hTERT (human telomerase ribonucleoprotein reverse transcriptase), and with a luciferase reporter to enable non-invasive bioluminescence imaging. The hTERT modified cells are tumorigenic in athymic rodents, and produce brainstem tumors that recapitulate the infiltrative growth of brainstem gliomas in patients.

Brain stem gliomas: a clinicopathological study from a single cancer center

Brain stem gliomas (BSG) are rare tumors occurring predominantly in childhood. They are mostly of astrocytic origin and are divided into infiltrative versus circumscribed types, with different prognoses. The diagnosis is mainly based on MRI findings, and biopsy is rarely performed. This is a retrospective study of BSG with available biopsies diagnosed at our center over 6-year period. Fifteen cases were identified, with a predominance of females. The median age was 7 years, and the mean duration of symptoms was <6 weeks in 58.3% (n = 7) of cases. MRI was typical of diffuse pontine gliomas in 64.3% (n = 9) of cases. Radiotherapy was the commonest modality of treatment, and the median overall survival was 21.7 months. Twelve cases were consistent with infiltrative astrocytoma of various grades (2 grade II, 7 grade III and 3 grade IV). Entrapped normal neurons and mitosis were the commonest findings indicating infiltrative growth and high grade, respectively, and those correlated significantly with immunostaining for neurofilament protein and Ki-67 of ≥3%. Overall survival correlated only with the duration of symptoms and tumor grade on biopsies. A limited panel of immunostains might be useful in undetermined cases to decide on the growth pattern and grade.

Stereotactic iodine-125 brachytherapy for treatment of inoperable focal brainstem gliomas of WHO grades I and II: feasibility and long-term outcome

Microsurgical resection is the most frequently suggested treatment option for accessible focal brainstem gliomas (F-BSG) of World Health Organization (WHO) grades I and II. Because of their location in the highly eloquent brain, however, resection is associated with permanent postoperative morbidity, ranging from 12 to 33 %. Only a few reports have suggested stereotactic brachytherapy (SBT) with implantation of iodine-125 seeds as a local treatment alternative. Between 1993 and 2010, 47 patients were treated with SBT (iodine-125 seeds; cumulative surface dose 50-65 Gy) for inoperable F-BSG, WHO grades I and II, in one of the largest reported patient series. We evaluated procedure-related complications, clinical outcome, and progression-free and overall survival (PFS, OS). Median follow-up was 81.6 months. Procedure-related mortality was zero. Within 30 days of seed implantation six patients (12.8 %) had transient neurological deficits. Two patients (4.3 %) deteriorated permanently. Space-occupying cysts occurred in six patients (12.8 %) after a median of 28.5 months, and required surgical intervention. Nine patients (19.1 %) presented with tumor relapse after a median of 56.6 months (range 7.9-118.0 months). For the remaining 38 patients complete response was observed for 23.4 %, partial response for 29.8 %, and stable disease for 27.7 %. Actuarial PFS was 97.7 ± 2.2, 92.8 ± 4.0, 81.2 ± 6.5, and 62.0 ± 10.4 % after 1, 2, 5, and 10 years, respectively. Corresponding OS was 100 ± 0.0 % (1 and 2 years), 97.4 ± 2.6 % (5 years), and 87.6 ± 7.0 % (10 years). SBT is a comparatively safe, minimally invasive, and highly effective local treatment option for patients with inoperable F-BSG WHO grades I and II; it merits further evaluation in prospective randomized trials.

Efficacy of vincristine administered via convection-enhanced delivery in a rodent brainstem tumor model documented by bioluminescence imaging

PURPOSE

Brain stem gliomas account for 20% of childhood brain tumors. Presently, there is no effective treatment for these tumors, and the prognosis remains poor. One reason for this is that chemotherapeutic drugs cannot cross the blood-brain barrier. In this study, we used a rodent brainstem tumor model, monitored both qualitatively and quantitatively, to examine the effectiveness of vincristine (VCR) administered via convection-enhanced delivery (CED).

METHODS

C6 rat glioblastoma cells, transduced with an oncoretroviral plasmid containing a luciferase coding sequence, were inoculated into Fischer 344 rat brainstems. Tumor growth was monitored by bioluminescence intensity (BLI), and tumor volume was calculated from serial histopathologic sections. Therapeutic efficacy of VCR delivered via CED was assessed. Intravenous (I.V.) and intraperitoneal (I.P.) drug administration were used as a comparison for CED efficacy.

RESULTS

BLI monitoring revealed progressive tumor growth in inoculated rats. Symptoms caused by tumor burden were evident 16-18 days after inoculation. BLI correlated quantitatively with tumor volume (r(2) = 0.9413), established by histopathological analysis of tumor growth within the pons. VCR administered through CED was more effective than I.V. or I.P. administration in reducing tumor size and increasing survival times. TUNEL assay results suggest that VCR induced glioblastoma cell apoptosis.

CONCLUSIONS

VCR administered by CED was effective in reducing tumors and prolonging survival time.

Expression of epidermal growth factor variant III (EGFRvIII) in pediatric diffuse intrinsic pontine gliomas

Despite numerous clinical trials over the past 2 decades, the overall survival for children diagnosed with diffuse intrinsic pontine glioma (DIPG) remains 9-10 months. Radiation therapy is the only treatment with proven effect and novel therapies are needed. Epidermal growth factor receptor variant III (EGFRvIII) is the most common variant of the epidermal growth factor receptor and is expressed in many tumor types but is rarely found in normal tissue. A peptide vaccine targeting EGFRvIII is currently undergoing investigation in phase 3 clinical trials for the treatment of newly diagnosed glioblastoma (GBM), the tumor in which this variant receptor was first discovered. In this study, we evaluated EGFRvIII expression in pediatric DIPG samples using immunohistochemistry with a double affinity purified antibody raised against the EGFRvIII peptide. Staining of pediatric DIPG histological samples revealed expression in 4 of 9 cases and the pattern of staining was consistent with what has been seen in EGFRvIII transfected cells as well as GBMs from adult trials. In addition, analysis of tumor samples collected immediately post mortem and of DIPG cells in culture by RT-PCR, western blot analysis, and flow cytometry confirmed EGFRvIII expression. We were therefore able to detect EGFRvIII expression in 6 of 11 DIPG cases. These data suggest that EGFRvIII warrants investigation as a target for these deadly pediatric tumors.

Neuroimaging of pediatric posterior fossa tumors including review of the literature

Conventional, anatomical MRI is an essential tool for diagnosis and evaluation of location, quality, and extent of posterior fossa tumors, but offers limited information regarding tumor grade and type. Advanced MRI techniques such as diffusion weighted imaging (DWI) and diffusion tensor imaging (DTI) may improve the specific diagnosis of brain tumors in the posterior fossa in children. In this review the conventional neuroimaging findings, as well as the DWI, and DTI characteristics of common pediatric posterior fossa tumors are discussed and summarized.

Father of neurosurgery: Harvey Cushing's early experience with a pediatric brainstem glioma at the Johns Hopkins Hospital

OBJECT

The early 20th century posed several challenges in the diagnosis and surgical treatment of intracranial tumors. However, this was a time in which more information was becoming more readily available based on pathological examination and surgical case reports. Such early work was crucial in shaping the current understanding of the nervous system and in developing modern treatment strategies. An early historical overview of the diagnosis and surgical interventions in pediatric patients with brainstem gliomas has not been described. Furthermore, Dr. Harvey Cushing's contributions to this field have not been reported.

METHODS

Following institutional review board approval, and through the courtesy of the Alan Mason Chesney Archives, the authors reviewed the Johns Hopkins Hospital surgical files dating from 1896 to 1912.

RESULTS

The authors describe Cushing's early experience with a pediatric brainstem glioma during his time as a young attending physician at the Johns Hopkins Hospital. The case, presented in 1909, described the clinical events in a 15-year-old schoolgirl who presented with signs of a cerebellopontine lesion. A suboccipital exploration was performed by Cushing; his findings and surgical approach are described.

CONCLUSIONS

Harvey Cushing's early contributions to the field of pediatric neurosurgery, and to the operative treatment of pediatric brainstem gliomas have remained largely unknown. The case presented here represents the early work of the American "Father of Neurosurgery."

Potential role for valproate in the treatment of high--risk brain tumors of childhood-results from a retrospective observational cohort study

Although substantial progress has been made in pediatric brain tumor management, patients with brainstem tumors and high-grade gliomas, as well as patients less than 3 years of age with high-risk malignant tumors, have a poorer prognosis. The authors have been treating these patients with radiotherapy and standard carboplatin and vincristine chemotherapy. Since January 2007 the authors have been using valproate as anticonvulsant for prophylaxis. The authors performed a retrospective cohort analysis of pediatric patients with high-risk brain tumors treated with chemotherapy, radiotherapy, and valproate prophylaxis, comparing this group with a historical control. The 2007-2008 group was comprised of 22 patients, 15 with brainstem tumors (7 diffuse intrinsic pontine glioma [DIPG], 3 focal, the remaining infiltrating with a solid portion), 4 with diencephalic tumors (2 thalamic), and 3 with supratentorial high-grade tumors (1 glioblastoma, 1 recurrent grade III ependymoma, 1 with gliomatosis). There were 15 patients alive (68%) after a mean follow-up time of 19 months. Survival function comparison by log rank test was highly significant (P = .004) with a hazard ratio of 0.31 (0.14-0.70). Radiological response showed 3 complete responses (14%), 8 partial responses (36%), 5 stable diseases (23%), and 5 progresssive diseases (23%). The authors hypothesize that valproate may have potentiated the antiangiogenic effect of vincristine, diminished expression of resistance to carboplatin, and sensitized tumor cells to radiotherapy. The authors suggest that clinical trials of carboplatin and vincristine associated with oral continuous low-dose valproate are indicated for pediatric patients with high-risk brain tumor.

Differential diagnosis of T2 hyperintense brainstem lesions: Part 2. Diffuse lesions

Diffuse brainstem lesions are poorly defined, often large abnormalities and include tumors (gliomas and lymphomas) vasculitis (Behçet's disease), traumatic brainstem injury, degenerative disorders (Wallerian degeneration), infections, processes secondary to systemic conditions (central pontine myelinolysis, hypertensive or hepatic encephalopathy), and ischemic pathology (leukoaraiosis). Magnetic resonance imaging is the most appropriate imaging modality to use in evaluating lesions of this type, but often findings are nonspecific. Therefore, radiologists need to bear in mind such additional information as patient age and clinical features in making a differential diagnosis.

Histology and molecular pathology of pediatric brain tumors

In recent years, brain tumors have become the single most frequent cause of cancer-related mortality in children, although their frequency is approximately 50% less than leukemia. According to the classification of the World Health Organization, histopathological diagnosis is of paramount importance for clinicians to choose the most appropriate treatment option and tailor treatment intensity to disease risk. However, histopathological assessment is often difficult, and adding molecular information to classic neuropathological analyses may help ensure diagnostic accuracy, improve risk stratification of patients within a given tumor entity, and help in identifying novel therapeutic targets for an individualized treatment approach. Therefore, this review focuses both on established histopathology as well as on molecular features in the most important brain tumors in children.

Mixed germ cell tumor of the midbrain. Case Report

This 14-year-old boy presented with left hemiparesis, gait disturbance, and multiple cranial nerve palsies. Magnetic resonance imaging revealed a multicystic mass with hemorrhagic fluid-fluid levels in the right midbrain, suggesting the presence of a cavernous malformation. Diffusion tensor imaging showed the mass to be close to the right corticospinal tract and ipsilateral medial lemniscus. Subtotal removal of the mass was performed via a right subtemporal approach. The histopathological diagnosis was of a mixed germ cell tumor (GCT) comprising mature teratoma and germinoma cells with syncytiotrophoblastic giant cells. The patient underwent postoperative chemotherapy and radiotherapy, and no tumor progression was found during 1 year of follow-up. Intracranial GCTs arise mainly in the pineal and the suprasellar area. Germ cell tumors in the brainstem are rare, with only 12 reported cases. Among these, 4 were in the midbrain and histologically were pure germinomas. To the authors' knowledge, this is the first reported case of a mixed GCT in the midbrain combining mature teratoma and germinoma cells.

A human brainstem glioma xenograft model enabled for bioluminescence imaging

Despite the use of radiation and chemotherapy, the prognosis for children with diffuse brainstem gliomas is extremely poor. There is a need for relevant brainstem tumor models that can be used to test new therapeutic agents and delivery systems in pre-clinical studies. We report the development of a brainstem-tumor model in rats and the application of bioluminescence imaging (BLI) for monitoring tumor growth and response to therapy as part of this model. Luciferase-modified human glioblastoma cells from five different tumor cell sources (either cell lines or serially-passaged xenografts) were implanted into the pontine tegmentum of athymic rats using an implantable guide-screw system. Tumor growth was monitored by BLI and tumor volume was calculated by three-dimensional measurements from serial histopathologic sections. To evaluate if this model would allow detection of therapeutic response, rats bearing brainstem U-87 MG or GS2 glioblastoma xenografts were treated with the DNA methylating agent temozolomide (TMZ). For each of the tumor cell sources tested, BLI monitoring revealed progressive tumor growth in all animals, and symptoms caused by tumor burden were evident 26–29 days after implantation of U-87 MG, U-251 MG, GBM6, and GBM14 cells, and 37–47 days after implantation of GS2 cells. Histopathologic analysis revealed tumor growth within the pons in all rats and BLI correlated quantitatively with tumor volume. Variable infiltration was evident among the different tumors, with GS2 tumor cells exhibiting the greatest degree of infiltration. TMZ treatment groups were included for experiments involving U-87 MG and GS2 cells, and in each case TMZ delayed tumor growth, as indicated by BLI monitoring, and significantly extended survival of animal subjects. Our results demonstrate the development of a brainstem tumor model in athymic rats, in which tumor growth and response to therapy can be accurately monitored by BLI. This model is well suited for pre-clinical testing of therapeutics that are being considered for treatment of patients with brainstem tumors.

Brainstem gliomas in children and adults

PURPOSE OF REVIEW

The purpose of this review is to determine if recent advances in diagnostic and treatment modalities result in improvement in the pattern of care of brainstem gliomas.

RECENT FINDINGS

New MRI techniques may contribute to differential diagnosis and aid neurosurgeons in removing resectable brainstem tumors. A better radiological analysis of these heterogeneous tumors improves their classification and helps to better distinguish prognosis subgroups. However, biopsy remains indicated in many contrast enhancing brainstem masses in adults because of the great variety of differential diagnosis.

SUMMARY

Diffuse brainstem glioma is the most common subtype of brainstem tumor and remains a devastating malignancy in children. Conventional radiotherapy is the standard of care and chemotherapy has been disappointing to date. Given the lack of efficacy of conventional drugs, a better understanding of the biology of this tumor is the key to more targeted therapy.