Side effects of oncologic therapies in the pediatric central nervous system: update on neuroimaging findings

Progression of brain injuries associated with methotrexate chemotherapy in childhood acute lymphoblastic leukemia

BACKGROUND

Brain bases and progression of methotrexate-associated neurotoxicity and cognitive disturbances remain unknown. We tested whether brain abnormalities worsen in proportion to intrathecal methotrexate(IT-MTX) doses.

METHODS

In this prospective, longitudinal study, we recruited 19 patients with newly diagnosed acute lymphoblastic leukemia 4-to-20 years of age and 20 matched controls. We collected MRI and neuropsychological assessments at a pre-methotrexate baseline and at week 9, week 22, and year 1 during treatment.

RESULTS

Patients had baseline abnormalities in cortical and subcortical gray matter(GM), white matter(WM) volumes and microstructure, regional cerebral blood flow, and neuronal density. Abnormalities of GM, blood flow, and metabolites worsened in direct proportions to IT-MTX doses. WM abnormalities persisted until week 22 but normalized by year 1. Brain injuries were localized to dorsal and ventral attentional and frontoparietal cognitive networks. Patients had cognitive deficits at baseline that persisted at 1-year follow-up.

CONCLUSIONS

Baseline abnormalities are likely a consequence of neuroinflammation and oxidative stress. Baseline abnormalities in WM microstructure and volumes, and blood flow persisted until week 22 but normalized by year 1, likely due to treatment and its effects on reducing inflammation. The cytotoxic effects of IT-MTX, however, likely contributed to continued, progressive cortical thinning and reductions in neuronal density, thereby contributing to enduring cognitive deficits.

IMPACT

Brain abnormalities at a pre-methotrexate baseline likely are due to acute illness. The cytotoxic effects of intrathecal MTX contribute to progressive cortical thinning, reductions in neuronal density, and enduring cognitive deficits. Baseline white matter abnormalities may have normalized via methotrexate treatment and decreasing neuroinflammation. Corticosteroid and leucovorin conferred neuroprotective effects. Our findings suggest that the administration of neuroprotective and anti-inflammatory agents should be considered even earlier than they are currently administered. The neuroprotective effects of leucovorin suggest that strategies may be developed that extend the duration of this intervention or adapt it for use in standard risk patients.

Mineralizing microangiopathy: radiological features of a "not uncommon" complication of chemoradiotherapy in pediatric cancer patients

Background

Mineralizing microangiopathy represents one of the delayed complications of radiotherapy and chemotherapy. We reviewed clinical and radiological data of pediatric cancer patients who presented with mineralizing microangiopathy. This is a retrospective analysis of the medical records of 37 cancer children treated with chemoradiotherapy presented with imaging criteria suspected of mineralizing microangiopathy admitted to our hospital during the period 2015–2020. The CT was reviewed for distribution of calcification and MRI for signal criteria.

This study aims to raise awareness among radiologists about radiological features of mineralizing microangiopathy during the sequential routine follow-up brain scans of pediatric cancer patients who received chemo, radio, or combined chemoradiotherapy and to identify changes as a long-term delayed complication of therapy and avoid misdiagnosis.

Results

Thirty-seven pediatric cancer patients (17 female and 20 males, aged 1.5–18 years) who had mineralizing microangiopathy were thoroughly investigated. Most of them (32 patients) had brain tumors and 5 patients had leukemia. Cranial radiotherapy and systemic chemotherapy were given to 33 patients, while nine patients received intrathecal chemotherapy. The interval needed to develop mineralizing microangiopathy ranged from 1 to 10 years after the end of treatment. CT detected calcification in the basal ganglia, being the most common location (32 cases), followed by cerebral gray–white matter interface in 26 patients, cerebellum (18), brain stem (13), thalamus (5), and caudate nucleus (4), while dural calcifications were found in only one patient. MRI was considered “positive” when T1 hyperintensity was noted in the anatomical location of CT detected calcification; it was positive in 29 cases.

Conclusion

Mineralizing microangiopathy is one of the delayed complications of chemoradiotherapy among pediatric cancer patients. The awareness of its radiological criteria is essential to avoid misdiagnosis. Early detection can alert pediatric oncologists to monitor neurotoxicity and help prevent long-term neurological sequels.

Imaging Findings in Children Presenting with CNS Nelarabine Toxicity

Nelarabine is a nucleoside analog critical for the treatment of patients with T-cell acute lymphoblastic leukemia/lymphoma. However, clinical peripheral and central neurologic adverse events associated with nelarabine administration have been reported. Neuroimaging of brain neurotoxicity has only been described in very few reports in pediatric patients so far. Six children with diagnosed T-cell acute lymphoblastic leukemia who clinically experienced possible, probable, or definite nelarabine-induced toxicity and underwent spine and/or brain MR imaging were reviewed. Neuroimaging findings showed a mixture of patterns including features of acute toxic leukoencephalopathy (seen in 6 cases), posterior reversible encephalopathy syndrome (2 cases), involvement of deep gray structures (1 case) and brainstem (2 cases), cranial and spinal neuropathy (2 cases each), and myelopathy (2 cases). Even though neuroimaging findings are nonspecific, the goal of this article was to alert the pediatric neuroradiologists, radiologists, and clinicians about the possibility of nelarabine-induced neurotoxicity and its broad neuroimaging spectrum.

Obesity as a Prognostic Factor of Central Nervous System Relapse in Children with Acute Lymphoblastic Leukemia: A Single-Centre Study and Literature Review

Relapse as the commonest treatment failure through chemotherapy of child presented with acute lymphoblastic leukemia (ALL) is usually within 3 years of remission. Central nervous system (CNS) is expected as a site of extramedullary relapse in 3–8% of child leukemia, often leading to a poor prognosis. A few patients may have headache and vomiting and can be diagnosed without difficulty. However, most patients present with asymptomatic conditions. Obesity has become one of the greatest reported complications of children ALL survivors. Rarely, obesity presentation can be the first manifestation of CNS leukemia. Here, we present three unusual cases with B-ALL presentation of obesity as the first symptom at the time of CNS relapse after achieving remission. This highly localized presentation is unusual and would hopefully inform clinicians to have a high index of suspicion for relapse in children with ALL.

Chemotherapy-related neurotoxicity in pediatric cancer patients: magnetic resonance imaging and clinical correlation

Background

Cancer is the second most common cause of death among children aged 1–14 years in the USA. Pediatric malignancies have elevated morbidity and mortality in the absence of proper treatment. Intensive treatment regimens have resulted in a significant increase in the number of survivors but also have been associated with the risk of developing neurotoxicity. The purpose of this study is to emphasize the role of advanced MRI techniques in the early detection of different chemotherapy neurotoxicities and make radiologists aware of them providing early management to prevent permanent damage.

Results

We evaluated 63 patients (43 males and 20 females), and their ages ranged from (2 to 17 years) with suspected chemotherapy-related neurotoxicity. MR examinations were performed with 1.5-T Philips systems. Clinical data were correlated with magnetic resonance imaging (MRI), and different treatment complications were diagnosed. All of our 63 patients were receiving chemotherapy treatment, and they developed different neurological symptoms. Patients diagnosed as posterior reversible encephalopathy syndrome were 41 with 8 patients had typical and 33 had atypical criteria, 16 patients diagnosed as cerebral venous sinus thrombosis with magnetic resonance venography (MRV) are the most important sequence that successfully diagnosed them, and finally, 6 patients diagnosed as methotrexate neurotoxicity with diffusion-weighted images (DWI) are the most important sequence for early diagnosis.

Conclusion

Chemotherapy is associated with certain neurotoxicities, conventional MRI can detect them, but by the use of advanced MRI techniques including MRV and DWI early detection of these neurotoxicities can occur. Therefore, the combination of conventional MRI together with advanced techniques improves the diagnostic efficacy of MRI in the early diagnosis of neurotoxicity.

Cystlike Lesions as a Late Sequela of Radiotherapy in Pediatric Patients

BACKGROUND AND PURPOSE

The developing nervous system is particularly vulnerable to late adverse effects of cranial radiation therapy, such as leukoencephalopathy, microbleeds, and cavernomas. Cystlike lesions have been rarely described and characterized in the literature. We aimed to characterize cystlike lesions, their risk factors, and association with other late adverse effects.

MATERIALS AND METHODS

Children treated for brain tumors during a 30-year period (n = 139) were included. We documented imaging findings, focusing on cystlike lesion development and its relationship with clinical history and other imaging findings. Multivariable analysis was performed using logistic regression and negative binomial regression models.

RESULTS

Cystlike lesions developed in 16.5% of patients treated with radiotherapy, with a median of 2 years until the development of the first lesion. For every 4-year age increase, there were 50% decreased odds of developing lesions and a 50% decrease in the average count of lesions. Females demonstrated a 4.00 rate ratio of developing a higher number of lesions. Patients who underwent chemoradiotherapy had 3.20 increased odds of developing cystlike lesions compared with patients with radiation therapy alone. A larger proportion of patients treated with methotrexate (25%) developed cystlike lesions, but this was not statistically significant. Cystlike lesions tended to develop in cerebral locations where leukoencephalopathy was worse. A strong relationship was found between the development of cystlike lesions and leukoencephalopathy severity.

CONCLUSIONS

Cystlike lesions are frequent and under-reported late adverse effects of cranial radiation therapy in children. Younger age, chemoradiotherapy, and the severity of leukoencephalopathy represent risk factors for the development of cystlike lesions.

Posterior Reversible Encephalopathy Syndrome in Childhood Hematological/Oncological Diseases: Multicenter Results

The aim of the study was to analyze the characteristics of posterior reversible encephalopathy syndrome (PRES) cases treated at 10 different institutions in our country. Fifty-eight patients diagnosed with PRES were included in this study. The data of PRES cases from 10 departments of pediatric hematology/oncology were analyzed. The mean age of the patients at the time of diagnosis of PRES was 8.95±3.66 years. Most patients (80.4%) had a primary diagnosis of acute leukemia. Patients received chemotherapy (71.4%) and/or used steroids within 14 days before the diagnosis of PRES (85.7%). Hypertension was found in 83.9% of the patients. Twenty-six patients had infections and 22 of them had febrile neutropenia. The most common electrolyte disorders were hypocalcemia, hypomagnesemia, and hypopotassemia. Six patients had tumor lysis syndrome and 4 had inappropriate antidiuretic hormone syndrome. Magnetic resonance imaging was used for diagnosis in all patients. The most commonly involved regions by magnetic resonance imaging were occipital (58%), parietal (51%), and frontal lobes (45%), respectively. Twenty-five patients required intensive care and 7 patients were intubated. In conclusion, PRES may develop during the follow-up and treatment of hematological diseases. In addition to steroid and intense combined chemotherapies, immunosuppressive agents and hypertension are also factors that may be responsible for PRES.

A Novel Approach to Understanding Social Behaviors in Pediatric Brain Tumor Survivors: A Pilot Study

BACKGROUND/OBJECTIVES

Pediatric brain tumor survivors (PBTS) are at risk of experiencing challenges in social adjustment. However, the specific social behaviors of PBTS have rarely been directly assessed. This pilot study explores the first novel use of the Autism Diagnostic Observation Schedule, second edition (ADOS-2), to evaluate the social behaviors of PBTS.

METHODS

Twenty-six PBTS (ages 9-17 years; M = 7.8 years from diagnosis; 52% male; 41% received radiation treatment) completed the ADOS-2. The proportion of the sample experiencing impairment was examined descriptively across all items of the ADOS-2, as well as by a summary "overall score" created for this study, and using the ADOS-2 "diagnostic algorithm" scores for autism. Social adjustment, cognitive, medical, and demographic variables were explored as correlates of the ADOS-2 "overall score".

RESULTS

Study recruitment was 34%, impeded by distance from the tertiary-care center. The percentage of PBTS experiencing detectable impairments ranged from 0% to 50% across ADOS-2 items. Cranial radiation treatment, lower IQ, and slower cognitive processing were associated with higher impairment on the ADOS-2 "overall score".

CONCLUSION

The ADOS-2 can be used to assess the discrete social behaviors of PBTS. This study provides a foundation for future investigations using the ADOS-2 to assess social behaviors in this population. Identifying specific social behavior difficulties in PBTS is key to refining much needed targeted social skills interventions for this population.

Role of magnetic resonance imaging in characterization of central nervous system lesions in pediatric patients with leukemia and post-treatment complications

Background

Leukemia is one of the most common fatal diseases in pediatric oncology. Recently, advances in drug therapy have improved the prognosis of acute leukemia with event-free survival of up to 60%; however, complications and adverse effects of the disease and anti-leukemic treatment have also increased. The CNS complications of leukemia can be classified into those that developed directly or indirectly from the underlying leukemic process and those that can be related to antileukemic therapy. MRI had improved early detection of CNS complications and proper management. The study aims to characterize the MRI findings caused by the leukemic involvement of CNS structures and treatment-associated CNS complications and assess its value in early management and avoidance of long-term side effects.

Results

The patient’s age ranged from 2 to 18 years with different types of leukemia classified regarding the time of presentation as pretreatment, during treatment phases, and post-treatment. Different MRI abnormalities were recorded and clinically correlated.

Conclusion

The neurological complications of leukemia have common presenting symptoms but varying imaging abnormalities. To reach the correct diagnosis, the presenting signs, symptoms, and laboratory data must be considered along with the radiologic findings. A diagnostic algorithm using conventional, post-contrast MRI, MR venography, along with diffusion-weighted MRI was of great value in early detection and differentiation of different CNS lesions detected in pediatric patients with leukemia and post-treatment CNS complications.

[Toxic changes of the central nervous system]

CLINICAL ISSUES

Various toxic agents can cause changes to the white matter of the brain leading to leukoencephalopathies. These changes often lead to signal alterations of the white matter with or without a diffusion restriction signal. White matter lesions can be reversible or irreversible. There are many differential diagnoses of toxic leukoencephalopathies.

PRACTICAL RECOMMENDATIONS

For the radiologist it is necessary to be familiar with the causes, the clinical and the imaging presentation of toxic leukoencephalopathies because early treatment often leads to improved prognosis.

Combination of clotam and vincristine enhances anti-proliferative effect in medulloblastoma cells

Medulloblastoma (MB) is characterized by highly invasive embryonal neuro-epithelial tumors that metastasize via cerebrospinal fluid. MB is difficult to treat and the chemotherapy is associated with significant toxicities and potential long-term disabilities. Previously, we showed that small molecule, clotam (tolfenamic acid: TA) inhibited MB cell proliferation and tumor growth in mice by targeting, survivin. Overexpression of survivin is associated with aggressiveness and poor prognosis in several cancers, including MB. The aim of this study was to test combination treatment involving Vincristine® (VCR), a standard chemotherapeutic drug for MB and TA against MB cells. DAOY and D283 MB cells were treated with 10 μg/mL TA or VCR (DAOY: 2 ng/mL; D283: 1 ng/mL) or combination (TA + VCR). These optimized doses were lower than individual IC₅₀ values. The effect of single or combination treatment on cell viability (CellTiterGlo kit), Combination Index (Chou-Talalay method based on median-drug effect analysis), activation of apoptosis and cell cycle modulation (by flow cytometry using Annexin V and propidium iodide respectively) and the expression of associated markers including survivin (Western immunoblot) were determined. Combination Index showed moderate synergistic cytotoxic effect in both cells. When compared to individual agents, the combination of TA and VCR increased MB cell growth inhibition, induced apoptosis and caused cell cycle (G₂/M phase) arrest. Survivin expression was also decreased by the combination treatment. TA is effective for inducing the anti-proliferative response of VCR in MB cells. MB has four distinct genetic/molecular subgroups. Experiments were conducted with MB cells representing two subgroups (DAOY: SHH group; D283: group 4/3). TA-induced inhibition of survivin expression potentially destabilizes mitotic microtubule assembly, sensitizing MB cells and enhancing the efficacy of VCR.

Toxic-Metabolic Neurologic Disorders in Children: A Neuroimaging Review

There are multiple causes of neurotoxicity in children including medications, extrinsic toxins and insults, illicit drugs, built up of toxic metabolites due to genetic or acquired disorders, and metabolic abnormalities. The review is centered on causes of neurotoxicity affecting the pediatric brain and producing typical and easily recognized imaging manifestations. Early identification of common and less common imaging findings may point toward the correct direction, and may facilitate early diagnosis and institution of appropriate treatment to reverse or at least limit the injury to the developing brain. Two common imaging patterns of neurotoxicity in children are the posterior reversible encephalopathy syndrome and acute toxic leukoencephalopathy that are usually related to chemotherapy and immunosuppression for common pediatric malignancies. Another well-described imaging pattern of injury in children involves reversible splenial lesions with or without associated white matter abnormalities. Multiple additional extrinsic causes of neurotoxicity are presented including radiation and chemoradiation, various medications and treatment regimens, poisoning, illicit drug use or accidental exposure, and the respective characteristic neuroimaging findings are highlighted. Intrinsic neurotoxicity may occur in the setting of inborn errors of metabolism or acquired progressive organ failure leading to build up of toxic metabolites. Additional intrinsic causes of neurotoxicity include metabolic derangements and characteristic imaging findings in all instances are reviewed. The goal of the article is to enhance familiarity of neurologists and neuroradiologists with the imaging appearance of common and less common toxic insults to the pediatric brain.

MR imaging findings in some rare neurological complications of paediatric cancer

Abstract

Neurological complications of paediatric cancers are a substantial problem. Complications can be primary from central nervous system (CNS) spread or secondary from indirect or remote effects of cancer, as well as cancer treatments such as chemotherapy and radiation therapy. In this review, we present the clinical and imaging findings of rare but important neurological complications in paediatric patients with cancer. Neurological complications are classified into three phases: pre-treatment, treatment and post-remission. Paraneoplastic neurological syndromes, hyperviscosity syndrome, haemophagocytic lymphohistiocytosis and infection are found in the pre-treatment phase, while Trousseau’s syndrome, posterior reversible encephalopathy syndrome and methotrexate neurotoxicity are found in the treatment phase; though some complications overlap between the pre-treatment and treatment phases. Hippocampal sclerosis, radiation induced tumour, radiation induced focal haemosiderin deposition and radiation-induced white matter injury are found in the post-remission phase. With increasingly long survival after treatment, CNS complications have become more common. It is critical for radiologists to recognise neurological complications related to paediatric cancer or treatment. Magnetic resonance imaging (MRI) plays a significant role in the recognition and proper management of the neurological complications of paediatric cancer.

Teaching Points

• Neurological complications of paediatric cancer include various entities.

• Neurological complications are classified into three phases: pre-treatment, treatment and post-remission.

• Radiologists should be familiar with clinical and imaging findings of neurological complications.

• MRI features may be characteristic and lead to early diagnosis and proper treatments.

Evaluation and treatment of Langerhans cell histiocytosis patients with central nervous system abnormalities: Current views and new vistas

Central nervous system (CNS) involvement in Langerhans cell histiocytosis (LCH) can include mass lesions of the hypothalamic pituitary axis, choroid plexus, cerebrum, and cerebellum or magnetic resonance imaging (MRI) signal abnormalities of the cerebellum, pons, and basal ganglia. The term neurodegenerative (ND) CNS-LCH has been given to the MRI signal abnormalities and neurologic dysfunction, although initially patients may have no clinical symptoms. Standardized evaluations to better understand the natural history and response to therapy are needed. We propose guidelines for clinical, radiologic, and physiologic tests as a framework for developing the best methods of evaluation, which can then be tested in prospective treatment protocols.

Toxins in Brain! Magnetic Resonance (MR) Imaging of Toxic Leukoencephalopathy - A Pictorial Essay

Toxic leukoencephalopathy results from damage to the white matter caused by various toxins. It manifests itself as white matter signal abnormalities with or without the presence of restricted diffusion. These changes are often reversible if the insulting agent is removed early, with the exception of posthypoxic leukoencephalopathy that can manifest itself 1–2 weeks after the initial insult. However, many other potential causes of white matter signal abnormalities can mimic the changes of toxic leukoencephalopathy. Thus, familiarity with the causes, clinical presentation and particularly imaging findings of toxic leukoencephalopathy is critical for early treatment and improved prognosis. The purpose of this pictorial essay is to familiarize the reader with the various causes of toxic leukoencephalopathy along with its differential diagnoses and mimics.

Magnetic resonance imaging patterns of treatment-related toxicity in the pediatric brain: an update and review of the literature

Treatment-related neurotoxicity is a potentially life-threatening clinical condition that can represent a diagnostic challenge. Differentiating diagnoses between therapy-associated brain injury and recurrent disease can be difficult, and the immediate recognition of neurotoxicity is crucial to providing correct therapeutic management, ensuring damage reversibility. For these purposes, the knowledge of clinical timing and specific treatment protocols is extremely important for interpreting MRI patterns. Neuroradiologic findings are heterogeneous and sometimes overlapping, representing the compounding effect of the different treatments. Moreover, MRI patterns can be acute, subacute or delayed and involve different brain regions, depending on (1) the mechanism of action of the specific medication and (2) which brain regions are selectively vulnerable to specific toxic effects. This review illustrates the most common radiologic appearance of radiotherapy, chemotherapy and medication-associated brain injury in children, with special focus on the application of advanced MRI techniques (diffusion, perfusion and proton spectroscopy) in the diagnosis of the underlying processes leading to brain toxicity.

False-positive magnetic resonance imaging findings in follow-up of pediatric patients with tumors of the central nervous system

Management of patients with central nervous system tumors relies largely on magnetic resonance imaging scans to document disease progression or recurrence. The finding of new lesions always presents the challenge of differentiating between post-surgical changes, radiation necrosis, gliosis, and tumor, submitting these patients to more aggressive therapy and more toxicity. We reviewed the medical records of three patients with primary central nervous system tumors treated at the Children’s Hospital Los Angeles who had new false-positive magnetic resonance imaging findings suggestive of tumor recurrence. All of them had complete total resection of primary tumor, had received involved-field radiation therapy, had biopsies confirming absence of viable tumor, and all three patients are long-term survivors. These cases exemplify that not everything that enhances on brain or spine magnetic resonance imaging is viable tumor, and a biopsy should always be considered in the decision-making process in evaluation of potentially recurrent central nervous system tumors in pediatric patients. A step-wise approach for such challenging cases is presented in this article.

Neurocognitive Late Effects of Chemotherapy in Survivors of Acute Lymphoblastic Leukemia: Focus on Methotrexate

Childhood cancer survivors frequently experience long-lasting consequences of chemotherapy on health outcomes. Neurocognitive late effects of chemotherapy occur in 40 - 60% of acute lymphoblastic leukemia (ALL) survivors. These deficits affect mental health, school performance, job success, and are associated with poor quality of life, therefore presenting a clinical challenge for psychiatrists. However, not all cancer survivors are impacted by treatment in the same manner and emerging evidence suggests that genetic variation may modulate neurocognitive outcomes. Much like other complex psychopathologies, neurocognitive deficits in cancer survivors are the result of complex interactions between genetic and environmental variables. This review describes adverse neurocognitive outcomes observed in survivors of acute lymphoblastic leukemia (ALL) and discusses genetic variability in biochemical pathways targeted by chemotherapeutic agents as a possible mechanism contributing to psychopathology in ALL survivors.

Detection of irreversible changes in susceptibility-weighted images after whole-brain irradiation of children

INTRODUCTION

Whole-brain irradiation is part of the therapy protocol for patients with medulloblastomas. Side effects and complications of radiation can be detected by follow-up magnetic resonance imaging (MRI). Susceptibility-weighted images (SWI) can detect even very small amounts of residual blood that cannot be shown with conventional MRI. The purpose of this study was to determine when and where SWI lesions appear after whole-brain irradiation.

METHODS

MRI follow-up of seven patients with medulloblastoma who were treated with whole-brain irradiation were analyzed retrospectively. SWI were part of the initial and follow-up MRI protocol. De novo SWI lesions, localization, and development over time were documented.

RESULTS

At time of irradiation, mean age of the patients was 13 years (±4 years). Earliest SWI lesions were detected 4 months after radiation treatment. In all patients, SWI lesions accumulated over time, although the individual number of SWI lesions varied. No specific dissemination of SWI lesions was observed.

CONCLUSION

Whole-brain irradiation can cause relatively early dot-like SWI lesions. The lesions are irreversible and accumulate over time. Histopathological correlation and clinical impact of these SWI lesions should be investigated.

Maturation of the adolescent brain

Adolescence is the developmental epoch during which children become adults - intellectually, physically, hormonally, and socially. Adolescence is a tumultuous time, full of changes and transformations. The pubertal transition to adulthood involves both gonadal and behavioral maturation. Magnetic resonance imaging studies have discovered that myelinogenesis, required for proper insulation and efficient neurocybernetics, continues from childhood and the brain's region-specific neurocircuitry remains structurally and functionally vulnerable to impulsive sex, food, and sleep habits. The maturation of the adolescent brain is also influenced by heredity, environment, and sex hormones (estrogen, progesterone, and testosterone), which play a crucial role in myelination. Furthermore, glutamatergic neurotransmission predominates, whereas gamma-aminobutyric acid neurotransmission remains under construction, and this might be responsible for immature and impulsive behavior and neurobehavioral excitement during adolescent life. The adolescent population is highly vulnerable to driving under the influence of alcohol and social maladjustments due to an immature limbic system and prefrontal cortex. Synaptic plasticity and the release of neurotransmitters may also be influenced by environmental neurotoxins and drugs of abuse including cigarettes, caffeine, and alcohol during adolescence. Adolescents may become involved with offensive crimes, irresponsible behavior, unprotected sex, juvenile courts, or even prison. According to a report by the Centers for Disease Control and Prevention, the major cause of death among the teenage population is due to injury and violence related to sex and substance abuse. Prenatal neglect, cigarette smoking, and alcohol consumption may also significantly impact maturation of the adolescent brain. Pharmacological interventions to regulate adolescent behavior have been attempted with limited success. Since several factors, including age, sex, disease, nutritional status, and substance abuse have a significant impact on the maturation of the adolescent brain, we have highlighted the influence of these clinically significant and socially important aspects in this report.

Benefits and limitations of errorless learning after surviving pediatric brain tumors: a case study

Survivors of childhood brain tumors often acquire complex cognitive difficulties including impairments in attention, processing speed, and different aspects of memory function. These impairments can affect their learning in the real world and in the classroom. However, the efficacy of memory rehabilitation techniques post treatment has not yet been assessed in these patients. We present the case of a 15-year-old boy, C.J., who acquired a profound episodic memory impairment due to a metastatic germ cell tumor and subsequent treatment. The focus of this study was the application of an errorless learning technique to a verbal learning task. We were interested to test whether C.J. would benefit from errorless learning as compared to errorful learning. Results of an experiment and a follow-up study indicated that C.J.'s learning was more efficient under errorless conditions, although access to the information from long-term memory remained cue dependent. Implications for learning with or without the support of episodic memory are discussed, and future directions for memory rehabilitation of brain tumor survivors are outlined.