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

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.

Synthetic Post-Contrast Imaging through Artificial Intelligence: Clinical Applications of Virtual and Augmented Contrast Media

Contrast media are widely diffused in biomedical imaging, due to their relevance in the diagnosis of numerous disorders. However, the risk of adverse reactions, the concern of potential damage to sensitive organs, and the recently described brain deposition of gadolinium salts, limit the use of contrast media in clinical practice. In recent years, the application of artificial intelligence (AI) techniques to biomedical imaging has led to the development of 'virtual' and 'augmented' contrasts. The idea behind these applications is to generate synthetic post-contrast images through AI computational modeling starting from the information available on other images acquired during the same scan. In these AI models, non-contrast images (virtual contrast) or low-dose post-contrast images (augmented contrast) are used as input data to generate synthetic post-contrast images, which are often undistinguishable from the native ones. In this review, we discuss the most recent advances of AI applications to biomedical imaging relative to synthetic contrast media.

Neuroimaging in cerebellar ataxia in childhood: A review

Ataxia is one of the most common pediatric movement disorders and can be caused by a large number of congenital and acquired diseases affecting the cerebellum or the vestibular or sensory system. It is mainly characterized by gait abnormalities, dysmetria, intention tremor, dysdiadochokinesia, dysarthria, and nystagmus. In young children, ataxia may manifest as the inability or refusal to walk. The diagnostic approach begins with a careful clinical history including the temporal evolution of ataxia and the inquiry of additional symptoms, is followed by a meticulous physical examination, and, depending on the results, is complemented by laboratory assays, electroencephalography, nerve conduction velocity, lumbar puncture, toxicology screening, genetic testing, and neuroimaging. Neuroimaging plays a pivotal role in either providing the final diagnosis, narrowing the differential diagnosis, or planning targeted further workup. In this review, we will focus on the most common form of ataxia in childhood, cerebellar ataxia (CA). We will discuss and summarize the neuroimaging findings of either the most common or the most important causes of CA in childhood or present causes of pediatric CA with pathognomonic findings on MRI. The various pediatric CAs will be categorized and presented according to (a) the cause of ataxia (acquired/disruptive vs. inherited/genetic) and (b) the temporal evolution of symptoms (acute/subacute, chronic, progressive, nonprogressive, and recurrent). In addition, several illustrative cases with their key imaging findings will be presented.

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.

Normal tissue tolerance amongst paediatric brain tumour patients- current evidence in proton radiotherapy

BACKGROUND

Proton radiotherapy (PT) is used increasingly for paediatric brain cancer patients. However, as demonstrated here, the knowledge on normal tissue dose constraints, to minimize side-effects, for this cohort is limited.

METHODS

A search strategy was systematically conducted on MEDLINE® database. 65 papers were evaluated ranging from 2013 to 2021.

RESULTS

Large variations in normal tissue tolerance and toxicity reporting across PT studies makes estimation of normal tissue dose constraints difficult, with the potential for significant late effects to go unmeasured. Mean dose delivered to the pituitary gland varies from 20 to 30 Gy across literature. Similarly, the hypothalamic dose delivery ranges from 20 to 54.6 Gy for paediatric patients.

CONCLUSION

There is a significant lack of radiobiological data for paediatric brain cancer patients undergoing proton therapy, often using data from x-ray radiotherapy and adult populations. The way forward is through standardisation of reporting in order to validate relevant dose constraints.

Magnetic resonance imaging of the brainstem in children, part 2: acquired pathology of the pediatric brainstem

Part 1 of this series of two articles describes conventional and advanced MRI techniques that are useful for evaluating brainstem pathologies. In addition, it provides a review of the embryology, normal progression of myelination, and clinically and radiologically salient imaging anatomy of the normal brainstem. Finally, it discusses congenital diseases of the brainstem with a focus on distinctive imaging features that allow for differentiating pathologies. Part 2 of this series of two articles includes discussion of neoplasms; infections; and vascular, demyelinating, toxic, metabolic and miscellaneous disease processes affecting the brainstem. The ultimate goal of this pair of articles is to empower the radiologist to add clinical value in the care of pediatric patients with brainstem pathologies.

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.

Comparative Study Between Functional MR Urography and Renal Scintigraphy to Evaluate Drainage Curves and Split Renal Function in Children With Congenital Anomalies of Kidney and Urinary Tract (CAKUT)

Background: Obstructive congenital anomalies of the kidney and urinary tract have a high risk of kidney failure if not surgically corrected. Dynamic renal scintigraphy is the gold standard technique to evaluate drainage curves and split renal function (SRF). Objectives: To compare functional magnetic resonance (MR) urography with dynamic renal scintigraphy in measuring volumetric SRF and in the classification of drainage curves in patients with congenital anomalies of the kidney and urinary tract. Materials and Methods: We retrospectively collected patients with hydroureteronephrosis or pelvicalyceal dilatation at renal ultrasound, who underwent both functional MR urography and dynamic renal scintigraphy (DRS) within 6 months. DRS studies were evaluated by a single nuclear medicine physician with a double reading. Functional MR urography renograms were blind evaluated twice by two radiologists. The functional MR urographyintra- and inter-reading agreements as well as the agreement between the two imaging techniques were calculated. SRF was evaluated by Area Under the Curve and Rutland-Patlak methods. Drainage curves were classified as normal, borderline or accumulation patterns by both the techniques. Results: Fifty-two children were studied, 14 with bilateral involvement. A total of 104 kidney-urinary tracts were considered: 38 normal and 66 dilated. Considering Area Under the Curve and Rutland-Patlak for SRF, the intra- and inter-reader agreements of functional MR urography had excellent and good results, respectively, and the two techniques demonstrated a good concordance (r2: 67% for Area Under the Curve and 72% for Rutland-Patlak). Considering drainage curves, the inter-readers agreement for functional MR urography and the concordance between the two techniques were moderate (Cohen's k, respectively, 55.7 and 56.3%). Conclusions: According to our results, there are no significant differences between functional MR urography and DRS in measuring volumetric SRF and in the classification of drainage curves in patients with congenital anomalies of the kidney and urinary tract.

Brain Imaging Findings and Neurologic Complications after Allogenic Hematopoietic Stem Cell Transplantation in Children

Hematopoietic stem cell transplantation (HSCT) is the only therapy for a subset of patients with malignant and nonmalignant diseases. Central nervous system (CNS) complications continue to be an important cause of morbidity and significantly contribute to mortality after HSCT. These complications include infections, cerebrovascular lesions, therapy-induced diseases, metabolic disturbances, and post-HSCT carcinogenesis. Following HSCT, three phases can be identified on the basis of the patient's immune status: the pre-engraftment period (<30 days after HSCT), the early postengraftment period (30-100 days after HSCT), and the late postengraftment period (>100 days after HSCT). There is a distinct relationship between the patient's degree of immunodeficiency after HSCT and the incidence of various complications that may occur. Early diagnosis of CNS complications is crucial for successful management and a good prognosis, and computed tomography and magnetic resonance imaging play an important role in achieving these goals. The global increase in the use of HSCT requires radiologists to be familiar with CNS complications, their relationship to the patient's immune status, and their imaging appearances. This article describes the clinical background of HSCT; reviews the incidence, causes, and timeline of brain complications in children who underwent allogenic HSCT; and identifies the characteristic imaging findings of these disorders. ^©RSNA, 2018.

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.

Dentate nucleus T1 hyperintensity: is it always gadolinium all that glitters?

In the last few years, several scientific papers and reports have demonstrated magnetic resonance (MR) signal intensity (SI) changes on pre-contrast T1-weighted images following multiple gadolinium-based contrast agents (GBCA) administrations, particularly following the exposure to linear GBCAs. Pathological animal and human post-mortem studies have confirmed the relationship between this radiological finding and the presence of gadolinium accumulation in vulnerable brain regions in patients with normal renal function. In this short communication, we report the case of a 15-year-old patient affected by b-cell acute lymphoblastic leukemia (bALL) who developed a hyperintense signal in the dentate nuclei following multiple administrations of a macrocyclic GBCA. The purpose of this report is to discuss possible differential diagnoses of this radiological finding with special focus on the differentiation between iron or manganese accumulation, post-irradiation changes and GBCA-related Gd deposition, highlighting the importance of the acquisition of accurate clinical data to improve our scientific knowledge.