Diffusion tensor imaging of brainstem tumors: axonal degeneration of motor and sensory tracts

NTMS based tractography and segmental diffusion analysis in patients with brainstem gliomas: Risk stratification and clinical potential

Introduction

Surgery on the brainstem level is associated with a high-risk of postoperative morbidity. Recently, we have introduced the combination of navigated transcranial magnetic stimulation (nTMS) and diffusion tensor imaging (DTI) tractography to define functionally relevant motor fibers tracts on the brainstem level to support operative planning and risk stratification in brainstem cavernomas.

Research question

Evaluate this method and assess it's clinical impact for the surgery of brainstem gliomas.

Material and methods

Patients with brainstem gliomas were examined preoperatively with motor nTMS and DTI tractography. A fractional anisotropy (FA) value of 75% of the individual FA threshold (FAT) was used to track descending corticospinal (CST) and -bulbar tracts (CBT). The distance between the tumor and the somatotopic tracts (hand, leg, face) was measured and diffusion parameters were correlated to the patients' outcome.

Results

12 patients were enrolled in this study, of which 6 underwent surgical resection, 5 received a stereotactic biopsy and 1 patient received conservative treatment. In all patients nTMS mapping and somatotopic tractography were performed successfully. Low FA values correlated with clinical symptoms revealing tract alteration by the tumor (p = 0.049). A tumor-tract distance (TTD) above 2 mm was the critical limit to achieve a safe complete tumor resection.

Discussion and conclusion

nTMS based DTI tractography combined with local diffusion analysis is a valuable tool for preoperative visualization and functional assessment of relevant motor fiber tracts, improving planning of safe entry corridors and perioperative risk stratification in brainstem gliomas tumors. This technique allows for customized treatment strategy to maximize patients' safety.

The Role of Advanced MRI Sequences in the Diagnosis and Follow-Up of Adult Brainstem Gliomas: A Neuroradiological Review

The 2021 WHO (World Health Organization) classification of brain tumors incorporated the rapid advances in the molecular, genetic, and pathogenesis understanding of brain tumor pathogenesis, behavior, and treatment response. It revolutionized brain tumor classification by placing great emphasis on molecular types and completely splitting adult-type and pediatric-type diffuse gliomas. Brainstem gliomas (BSGs) are the leading primary tumors of the brainstem, although they are quite uncommon in adults compared with the pediatric population, representing less than 2% of adult gliomas. Surgery is not always the treatment of choice since resection is rarely feasible and does not improve overall survival, and biopsies are not generally performed since the location is treacherous. Therefore, MRI (Magnetic Resonance Imaging) without and with gadolinium administration represents the optimal noninvasive radiological technique to suggest brainstem gliomas diagnosis, plan a multidisciplinary treatment and for follow-up evaluations. The MRI protocol encompasses morphological sequences as well as functional and advanced sequences, such as DWI/ADC (Diffusion-Weighted Imaging/Apparent Diffusion Coefficient), DTI (Diffusion Tensor Imaging), PWI (Perfusion-Weighted Imaging), and MRS (Magnetic Resonance Spectroscopy), which improve the accuracy of the diagnosis of BSGs by adding substantial information regarding the cellularity, the infiltrative behavior toward the v fiber tracts, the vascularity, and the molecular changes. Brainstem gliomas have been divided into four categories on the basis of their MRI radiological appearance, including diffuse intrinsic low-grade gliomas, enhancing malignant gliomas, localized tectal gliomas, and other forms. The aim of our review is to provide insight into the role of advanced MRI sequences in the diagnosis and follow-up of adult brainstem gliomas.

Radiation dose response of neurologic symptoms during conformal radiotherapy for diffuse intrinsic pontine glioma

PURPOSE

To estimate the rate and magnitude of neurologic symptom change during radiation therapy (RT) and impact of symptom change on survival outcomes in patients with diffuse intrinsic pontine glioma (DIPG).

METHODS

From 2006 to 2014, 108 patients with newly diagnosed DIPG were treated with conventionally fractionated radiation therapy (RT) to 54 Gy (median) at our institution. The presence and severity of neurologic symptoms related to cranial neuropathy (CN) and cerebellar (CB) and long-tract (LT) signs was reviewed before and weekly during RT for each patient. The rate and magnitude of change for each symptom category was evaluated according to accumulated RT dose. The impact of clinical factors and radiation dose-volume parameters was determined using Cox proportional hazards models.

RESULTS

Median dose to first sign of symptomatic improvement was 16.2 Gy (CN), 19.8 Gy (LT) and 21.6 Gy (CB). Most patients showed an improvement by 20 Gy. Larger uninvolved brainstem volume, alone or normalized to total brain (TB) or posterior fossa volume (PF), was associated with shorter time to LT sign improvement (P = 0.044, P = 0.033, and P = 0.05, respectively). Patients with any improvement in CN experienced significantly, yet modestly, prolonged progression-free survival (PFS) and overall survival (OS) (P = 0.002 and P = 0.008, respectively). Tumor volume, with or without normalization to TB or PF, was not significantly associated with PFS or OS.

CONCLUSIONS

Low cumulative RT doses resulted in neurologic improvement in most patients with DIPG. The volume of brainstem spared by tumor influenced time to symptomatic improvement. Neurologic improvement during RT was associated with superior survival.

Clinical tolerance of corticospinal tracts in convection-enhanced delivery to the brainstem

OBJECTIVE

Convection-enhanced delivery (CED) has been explored as a therapeutic strategy for diffuse intrinsic pontine glioma (DIPG). Variables that may affect tolerance include infusate volume, infusion rate, catheter trajectory, and target position. Supratentorial approaches for catheter placement and infusate distribution patterns may conflict with corticospinal tracts (CSTs). The clinical relevance of these anatomical constraints has not been described. The authors report their experience using CED in the brainstem as it relates to anatomical CST conflict and association with clinical tolerance.

METHODS

In a phase I clinical trial of CED for DIPG (clinical trial registration no. NCT01502917, clinicaltrials.gov), a flexible infusion catheter was placed with MRI guidance for infusion of 124I-8H9, a radioimmunotherapeutic agent. Intra- and postprocedural MR images were analyzed to identify catheter trajectories and changes in T2-weighted signal intensity to approximate volume of distribution (Vd). Intersection of CST by the catheter and overlap between Vd and CST were recorded and their correlation with motor deficits was evaluated.

RESULTS

Thirty-one patients with a mean age of 7.6 years (range 3.2-18 years) underwent 39 catheter insertions for CED between 2012 and 2017. Thirty catheter insertions had tractography data available for analysis. The mean trajectory length was 105.5 mm (range 92.7-121.6 mm). The mean number of intersections of CST by catheter was 2.2 (range 0-3) and the mean intersecting length was 18.9 mm (range 0-44.2 mm). The first 9 infusions in the highest dose level (range 3.84-4.54 ml infusate) were analyzed for Vd overlap with CST. In this group, the mean age was 7.6 years (range 5.8-10.3 years), the mean trajectory length was 109.5 mm (range 102.6-122.3 mm), and the mean overlap between Vd and CST was 5.5 cm3. For catheter placement-related adverse events, 1 patient (3%) had worsening of a contralateral facial nerve palsy following the procedure with two CST intersections, an intersecting distance of 31.7 mm, and an overlap between Vd and CST of 3.64 cm3. For infusion-related adverse events, transient postinfusion deficits were noted in 3 patients in the highest dose level, with a mean number of 2 intersections of CST by catheter, mean intersecting length of 12.9 mm, and mean overlap between Vd and CST of 6.3 cm3.

CONCLUSIONS

A supratentorial approach to the brainstem crossing the CST resulted in one worsened neurological deficit. There does not appear to be a significant risk requiring avoidance of dominant motor fiber tracts with catheter trajectory planning. There was no correlation between Vd-CST overlap and neurological adverse events in this cohort.Clinical trial registration no.: NCT01502917 (clinicaltrials.gov).

Connectivity-based segmentation of the brainstem by probabilistic tractography

Diffusion magnetic resonance imaging is a non-invasive tool increasingly used for the investigation of brain connectivity in vivo. In this paper we propose a method that allows segmentation of the brainstem to four subregions (frontopontine, motor, sensory and reticular) based on connections to supratentorial structures, thereby eliminating the need for using anatomical landmarks within the brainstem for the identification of these subregions. The feasibility of connectivity-based brainstem segmentation was investigated in a group of healthy subjects (n = 20). Multifiber probabilistic tractography was performed using the FMRIB Software Library, and connections between a pontomesencephalic seed mask and four supratentorial target regions (anterior and posterior limbs of the internal capsule, sensory and medial thalamus) were used to determine connectivity maps of the brainstem. Results were compared with a neuroanatomy atlas and histological sections, confirming good anatomic correspondence. The four subregions detected by the connectivity-based segmentation showed good intersubject reproducibility. The presented method may be a potential tool to investigate brainstem connectivity in diseases that distort normal anatomy, and quantitative analyses of the diffusion-related parameters may provide additional information on the involvement of brainstem pathways in certain disease states (e.g., traumatic brain injury, demyelinating disorders, brainstem tumors). The potential clinical applicability of the method is demonstrated in two cases of severe traumatic brain injury.

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.

Re-Examining the Need for Tissue Diagnosis in Pediatric Diffuse Intrinsic Pontine Gliomas: A Review

Diffuse intrinsic pontine glioma (DIPG) is a malignant brain tumor of childhood that carries an extremely poor prognosis. There are ~200-300 new cases diagnosed each year, [1, 2] and little progress has been made in changing the prognosis and outcome of the tumor since it was first documented in the literature in 1926 [3]. The median overall survival is 8-11 months [4], with an overall survival rate of 30% at 1 year, and less than 10% at 2 years [4]. This review will provide background information on DIPGs, a historical look at the trends in caring for DIPG, and current trends in diagnosis and treatment. By changing the way we care for these terminal tumors, we can work towards having a better understanding of the underlying molecular biology, and attempt to develop better chemotherapeutic tools to combat the disease.

Magnetic resonance imaging based functional imaging in paediatric oncology

Imaging is central to management of solid tumours in children. Conventional magnetic resonance imaging (MRI) is the standard imaging modality for tumours of the central nervous system (CNS) and limbs and is increasingly used in the abdomen. It provides excellent structural detail, but imparts limited information about tumour type, aggressiveness, metastatic potential or early treatment response. MRI based functional imaging techniques, such as magnetic resonance spectroscopy, diffusion and perfusion weighted imaging, probe tissue properties to provide clinically important information about metabolites, structure and blood flow. This review describes the role of and evidence behind these functional imaging techniques in paediatric oncology and implications for integrating them into routine clinical practice.

Preliminary experience with diffusion tensor imaging before and after re-irradiation treatments in children with progressive diffuse pontine glioma

PURPOSE

The purpose of this study is to evaluate quantitative changes in diffusion tensor imaging (DTI) tractography and fractional anisotropy (FA) of the pons along with clinical correlation, in patients who receive re-irradiation for progressive diffuse intrinsic pontine glioma (DIPG).

METHODS

A retrospective case review of children with progressive DIPG who received re-irradiation at our institution from 2007 to 2011 after approval from the Institutional Review Board was performed. Tractography analysis and FA were analyzed pre and post-re-irradiation, and correlation with clinical features and MR imaging was performed.

RESULTS

DTI analysis showed reduced values of FA on tumor progression. Increase in the FA values was noted after re-irradiation in these patients. This correlated with clinical improvement. These changes were concordant with the 3D tractography analysis which showed better visualization of the corticospinal tracts as they course through brainstem and posterior transverse pontine fibers following re-irradiation.

CONCLUSION

Serial changes in the FA values using DTI could provide clinically more correlative information in patients with progressive DIPG, who receive re-irradiation. Though the use and results of this modality has been reported in the newly diagnosed DIPG before, evaluation of DTI in children who receive re-irradiation for progressive DIPG has not been reported earlier. Though limited by the small sample size and treatment variability, this study for the first time shows the preliminary experience, potential, and likely efficacy of complementing DTI analysis to routine neuroimaging also in patients re-irradiated for progressive DIPG to better assess treatment response.

Brainstem gliomas

Historically, brainstem gliomas have been considered as a single entity. Since the introduction of magnetic resonance (MR) imaging in the late 1980s, these tumors are now regarded as a heterogeneous group of neoplasms with different age of onset, clinical and radiologic presentation, and varying behavior and natural history. This article describes the different subtypes of brainstem gliomas in children and adults. We focus on recent advances in MR such as MR spectroscopy, MR perfusion, and diffusion tensor imaging that often strongly suggest the histopathologic diagnosis of the lesion.

Feasibility of creating a high-resolution 3D diffusion tensor imaging based atlas of the human brainstem: a case study at 11.7 T

A three-dimensional stereotaxic atlas of the human brainstem based on high resolution ex vivo diffusion tensor imaging (DTI) is introduced. The atlas consists of high resolution (125-255 μm isotropic) three-dimensional DT images of the formalin-fixed brainstem acquired at 11.7 T. The DTI data revealed microscopic neuroanatomical details, allowing three-dimensional visualization and reconstruction of fiber pathways including the decussation of the pyramidal tract fibers, and interdigitating fascicles of the corticospinal and transverse pontine fibers. Additionally, strong gray-white matter contrasts in the apparent diffusion coefficient (ADC) maps enabled precise delineation of gray matter nuclei in the brainstem, including the cranial nerve and the inferior olivary nuclei. Comparison with myelin-stained histology shows that at the level of resolution achieved in this study, the structural details resolved with DTI contrasts in the brainstem were comparable to anatomical delineation obtained with histological sectioning. Major neural structures delineated from DTI contrasts in the brainstem are segmented and three-dimensionally reconstructed. Further, the ex vivo DTI data are nonlinearly mapped to a widely-used in vivo human brain atlas, to construct a high-resolution atlas of the brainstem in the Montreal Neurological Institute (MNI) stereotaxic coordinate space. The results demonstrate the feasibility of developing a 3D DTI based atlas for detailed characterization of brainstem neuroanatomy with high resolution and contrasts, which will be a useful resource for research and clinical applications.

Reduced-distortion diffusion MRI of the craniovertebral junction

BACKGROUND AND PURPOSE

CVJ lesion suffers from a high sensitivity to susceptibility and distortion artifacts, which sometimes makes diffusion image difficult to interpret. Our purpose was to evaluate the potential for diffusion MR imaging using RS-EPI compared with SS-EPI in the assessment of the CVJ.

MATERIALS AND METHODS

RS-EPI and SS-EPI DTI images were acquired from 10 healthy volunteers using 3T MRI with a 32-channel head coil. For both sequences, the following parameters were used: 1-mm(2) in-plane resolution; 3-mm section thickness; TR = 5200 ms; 1 acquisition at b = 0 and 12 different encoding directions at b = 1000 seconds/mm(2). The RS-EPI sequence scan time was 9.44 minutes (1 average). The SS-EPI sequence was 9.37 minutes (8 averages). Diffusion tensor calculation and image analysis were performed using DTIStudio software. Diffusion trace images and color-coded fiber orientation maps were evaluated by 2 independent readers for distortion and delineation of fine structure using a semiquantitative scale in selected landmark locations. The absolute distances between the temporal base and the cerebellar contour between the T2-weighted images and the diffusion trace images obtained with RS-EPI and SS-EPI were also compared.

RESULTS

The contours of the temporal lobe and cerebellum were better delineated and distortion artifacts were clearly reduced with the RS-EPI sequence. More fine structures were also visible in the brain stem and cerebellum with the RS-EPI sequence. The amount of distortion was significantly reduced with RS-EPI compared with SS-EPI (P < .01).

CONCLUSIONS

The RS-EPI DTI sequence was less prone to geometric distortion than the SS-EPI sequence and allowed a better delineation of CVJ internal structure. Although the acquisition time is still relatively long, the RS-EPI appears as a promising approach to perform DTI studies in CVJ lesions, such as brain stem ischemia, neurodegenerative diseases, brain and skull base tumors, or inflammation.

Brain tumor therapy-induced changes in normal-appearing brainstem measured with longitudinal diffusion tensor imaging

PURPOSE

To characterize therapy-induced changes in normal-appearing brainstems of childhood brain tumor patients by serial diffusion tensor imaging (DTI).

METHODS AND MATERIALS

We analyzed 109 DTI studies from 20 brain tumor patients, aged 4 to 23 years, with normal-appearing brainstems included in the treatment fields. Those with medulloblastomas, supratentorial primitive neuroectodermal tumors, and atypical teratoid rhabdoid tumors (n = 10) received postoperative craniospinal irradiation (23.4-39.6 Gy) and a cumulative dose of 55.8 Gy to the primary site, followed by four cycles of high-dose chemotherapy. Patients with high-grade gliomas (n = 10) received erlotinib during and after irradiation (54-59.4 Gy). Parametric maps of fractional anisotropy (FA) and apparent diffusion coefficient (ADC) were computed and spatially registered to three-dimensional radiation dose data. Volumes of interest included corticospinal tracts, medial lemnisci, and the pons. Serving as an age-related benchmark for comparison, 37 DTI studies from 20 healthy volunteers, aged 6 to 25 years, were included in the analysis.

RESULTS

The median DTI follow-up time was 3.5 years (range, 1.6-5.0 years). The median mean dose to the pons was 56 Gy (range, 7-59 Gy). Three patterns were seen in longitudinal FA and apparent diffusion coefficient changes: (1) a stable or normal developing time trend, (2) initial deviation from normal with subsequent recovery, and (3) progressive deviation without evidence of complete recovery. The maximal decline in FA often occurred 1.5 to 3.5 years after the start of radiation therapy. A full recovery time trend could be observed within 4 years. Patients with incomplete recovery often had a larger decline in FA within the first year. Radiation dose alone did not predict long-term recovery patterns.

CONCLUSIONS

Variations existed among individual patients after therapy in longitudinal evolution of brainstem white matter injury and recovery. Early response in brainstem anisotropy may serve as an indicator of the recovery time trend over 5 years after radiation therapy.

DTI assessment of the brainstem white matter tracts in pediatric BSG before and after therapy: a report from the Pediatric Brain Tumor Consortium

PURPOSE

To assess changes in apparent diffusion coefficient (ADC) and fractional anisotropy (FA) values in brainstem gliomas (BSG) in children and to observe the temporal evolution of changes in the white matter tracts following therapy using diffusion tensor imaging (DTI) analysis.

METHODS

Serial ADC and FA measurements were obtained in three patients with newly diagnosed BSG on two approved treatment protocols. Values were compared with a set of normative ADC, FA, and eigenvalues of age-matched children of the corticospinal, transverse pontine and medial lemniscal tracts. Fiber tracking of the tracts coursing through the brainstem was performed using standard diffusion tractography analysis.

RESULTS

We found increased ADC values within tumor at baseline compared to age-matched controls, with subsequent drop following treatment and subsequent increase with recurrence. Correspondingly, FA values were reduced at presentation, but transiently recovered during the phase of tumor response to treatment, and finally decreased significantly during tumor progression. These changes were concordant with the tractography analysis of white matter tracts in the brainstem. Based on these results, we suggest that initial changes in ADC and FA values reflects tract infiltration by tumor, but not complete disruption, whereas tumor progression results in complete loss of anisotropy possibly due to tract disruption.

CONCLUSION

Serial changes in ADC and FA values and tractography data in pediatric BSG suggest initial tumor infiltration, with transient improvement on treatment and subsequent loss of tract anisotropy during tumor progression. This technique may have potential use in assessing response to treatment regimens for pediatric BSG.

Quantitative diffusion-weighted and dynamic susceptibility-weighted contrast-enhanced perfusion MR imaging analysis of T2 hypointense lesion components in pediatric diffuse intrinsic pontine glioma

BACKGROUND AND PURPOSE

Focal anaplasia characterized by T2 hypointensity, signal-intensity enhancement on postcontrast T1-weighted MR imaging and restricted water diffusion has been reported in a patient with juvenile pilocytic astrocytoma. We identified T2(HOF) with these MR imaging characteristics in children with DIPG and hypothesized that these represent areas of focal anaplasia; and may, therefore, have increased perfusion properties and should be characterized by increased perfusion. Thus, we used DSC to investigate our hypothesis.

MATERIALS AND METHODS

We retrospectively reviewed the baseline MR imaging scans of 86 patients (49 girls, 37 boys; median age, 6.1 years; range, 1.1-17.6 years) treated for DIPG at our hospital (2004-2009). T2(HOF) with the described MR imaging characteristics was identified in 10 patients. We used a region of interest-based approach to compare the ADC, FA, rCBV, rCBF, and rMTT of T2(HOF) with those of the typical T2(HRT).

RESULTS

The ADC of T2(HOF) with the specified MR imaging characteristics was significantly lower than that of T2(HRT) (range, 0.71-1.95 μm(2)/ms versus 1.36-2.13 μm(2)/ms; P < .01); and the FA (range, 0.12-0.34 versus 0.07-0.24; P = .03) and rCBV (range, 0.4-2.62 versus 0.23-1.57; P = .01) values of T2(HOF)s were significantly higher.

CONCLUSIONS

Our data suggest that T2(HOF) in DIPG may represent areas of focal anaplasia and underline the importance of regional, rather than global, tumor-field analysis. T2(HOF) may be the ideal target when stereotactic biopsy of tumors that present with an inhomogeneous T2 signal intensity is considered.

Role of diffusion tensor imaging in resection of thalamic juvenile pilocytic astrocytoma

OBJECT

The choice of surgical approach during resection of a thalamic juvenile pilocytic astrocytoma (JPA) is dictated by the location of the displaced normal thalamus and posterior limb of the internal capsule (PLIC). Diffusion tensor (DT) imaging and white matter tractography can identify the location of the PLIC in relation to the tumor and may be useful in planning the operative trajectory.

METHODS

Diffusion tensor imaging was used to localize the PLIC on preoperative MR imaging in 6 children undergoing resection of thalamic JPAs. After review of the standard T2-weighted MR imaging sequences, the anticipated position of the PLIC was determined. This result was compared with the location of the PLIC determined by a blinded radiologist with the use of DT imaging. The utility of DT imaging in determining the surgical approach to a thalamic JPA, degree of resection, and neurological outcomes were all evaluated.

RESULTS

Diffusion tensor imaging confirmed the expected location of the PLIC as approximated on conventional T2-weighted images in all 6 cases. In 1 patient in particular, unexpected medial deviation of the PLIC was identified, and this proved useful in tailoring the approach to a more lateral trajectory. Gross-total resection of all cystic and solid tumor components was confirmed on postoperative imaging in all cases. All patients experienced mild to moderate worsening of neurological status immediately following resection, but 4 of 6 patients were back to their preoperative baseline at 6-month follow-up.

CONCLUSIONS

Diffusion tensor imaging and white matter tractography successfully identified the white matter fibers emanating from the precentral gyrus within the PLIC in children with thalamic JPAs prior to surgery. Diffusion tensor imaging served as a valuable tool for stereotactic planning of operative approaches to thalamic JPAs. Localizing the position of the PLIC helped minimize potential neurological morbidity and facilitated gross-total resection.

Clinical, radiologic and pathologic features and outcome following surgery for cervicomedullary gliomas in children

INTRODUCTION

Surgical resection is generally recommended for cervicomedullary tumors, but morbidity of resection may be significant. This study sought to identify MRI characteristics that might predict morbidity and extent of resection.

MATERIALS AND METHODS

A retrospective review was performed of MRI findings, histopathology, extent, and morbidity of resection in cervicomedullary gliomas undergoing resection during 1985-2008.

RESULTS

Of 78 brainstem tumors, nine cervicomedullary tumors undergoing resection were identified: two pilocytic astrocytomas, two gangliogliomas, and five grade II astrocytomas. Mean age was 6.3 years (range 1.7-11.2 years). Initial treatment was surgery in seven: biopsy (1), <25% resection (4), and 25-50% resections (2). Bulbar worsening occurred in five of six patients with interposed areas of non-enhancement versus one of three patients without interposed non-enhancing tissue (P = 0.014). Additionally, bulbar worsening occurred in five of five patients with a poorly defined tumor/brainstem interface and abnormal low T1 signal extending beyond obvious tumor into the brainstem versus one of four with a well-defined tumor margin (P = 0.008). Following chemo- or radiotherapy, the definition of the brainstem/tumor interface improved. In four patients undergoing surgery after chemo/radiotherapy, more extensive resections were achieved without neurologic worsening: >80% in three and 30% in one.

CONCLUSION

A less aggressive initial surgical approach, supplemented by postoperative chemotherapy, designed to preserve brainstem function, is proposed for patients with interposed non-enhancing tissue continuous with normal cervical cord or medulla and/or a poorly defined ventral tumor/brainstem interface with abnormal low T1 signal extending beyond obvious tumor into the brainstem.

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.

Treatment of diffuse intrinsic brainstem gliomas: failed approaches and future strategies

Diffuse intrinsic pontine gliomas constitute ~ 60-75% of tumors found within the pediatric brainstem. These malignant lesions present with rapidly progressive symptoms such as cranial nerve, long tract, or cerebellar dysfunctions. Magnetic resonance imaging is usually sufficient to establish the diagnosis and obviates the need for surgical biopsy in most cases. The prognosis of the disease is dismal, and the median survival is < 12 months. Resection is not a viable option. Standard therapy involves radiotherapy, which produces transient neurological improvement with a progression-free survival benefit, but provides no improvement in overall survival. Clinical trials have been conducted to assess the efficacy of chemotherapeutic and biological agents in the treatment of diffuse pontine gliomas. In this review, the authors discuss recent studies in which systemic therapy was administered prior to, concomitantly with, or after radiotherapy. For future perspective, the discussion includes a rationale for stereotactic biopsies as well as possible therapeutic options of local chemotherapy in these lesions.