WMD was diagnosed in 28 children and subclassified into circumscribed white matter lesions (WML) and diffuse atrophy. WML were the most common finding ( n=13), followed by atrophy ( n=7) and the combination of both ( n=8). Statistical analysis revealed slightly more frequent atrophy in children younger than 5 years. WML could be linked with supratentorial location of the tumor, follow-up longer than 5 years, and the presence of a ventricular shunt. Intrathecal chemotherapy was also a factor, but because of the small sample size of the group this might not be valid. None of the children had neurological deficits attributed to these findings, but the impact on neuropsychological development was not determined.

Background: Rebound thymic hyperplasia (RTH) is a common phenomenon caused by stress factors such as chemotherapy (CTX) or radiotherapy, with an incidence between 44% and 67.7% in pediatric lymphoma. Misinterpretation of RTH and thymic lymphoma relapse (LR) may lead to unnecessary diagnostic procedures including invasive biopsies or treatment intensification. The aim of this study was to identify parameters that differentiate between RTH and thymic LR in the anterior mediastinum.Methods: After completion of CTX, we analyzed computed tomographies (CTs) and magnetic resonance images (MRIs) of 291 patients with classical Hodgkin lymphoma (CHL) and adequate imaging available from the European Network for Pediatric Hodgkin lymphoma C1 trial. In all patients with biopsy-proven LR, an additional fluorodeoxyglucose (FDG)-positron emission tomography (PET)-CT was assessed.Structure and morphologic configuration in addition to calcifications and presence of multiple masses in the thymic region and signs of extrathymic LR were evaluated. Results:After CTX, a significant volume increase of new or growing masses in the thymic space occurred in 133 of 291 patients. Without biopsy, only 98 patients could be identified as RTH or LR. No single finding related to thymic regrowth allowed differentiation between RTH and LR. However, the vast majority of cases with thymic LR presented with additional increasing tumor masses (33/34). All RTH patients (64/64) presented with isolated thymic growth. Conclusion:Isolated thymic LR is very uncommon. CHL relapse should be suspected when increasing tumor masses are present in distant sites outside of the thymic area.Conversely, if regrowth of lymphoma in other sites can be excluded, isolated thymic mass after CTX likely represents RTH.

Background Rebound thymic hyperplasia (RTH) is a common phenomenon caused by stress factors such as chemo- (CTX) or radiotherapy with an incidence of up to 40%. Misinterpretation of RTH and thymic lymphoma relapse (LR) may lead to unnecessary diagnostic procedures including invasive biopsies or treatment intensification. The aim of this study was to identify parameters that differentiate between RTH and thymic LR in the anterior mediastinum. Methods After completion of CTX, we analyzed CTs and MRIs of 291 patients with classical Hodgkin lymphoma (CHL) and adequate imaging available from the European Network for Pediatric Hodgkin lymphoma C1-trial. In all patients with biopsy proven LR an additional FDG-PET-CT was assessed. Structure and morphologic configuration in addition to calcifications and presence of multiple masses in the thymic region and signs of extrathymic LR were evaluated. Results After CTX, a significant volume increase of a new or growing mass in the thymic space occurred in 133 of 291 patients. Without biopsy only 100 patients could be identified as RTH or LR. No single finding related to thymic regrowth allowed differentiation between RTH and LR. However, the vast majority of cases with thymic LR presented with additional increasing tumor masses (34/35). All RTH patients (65/65) presented with isolated thymic growth. Conclusion Isolated thymic LR is very uncommon. CHL relapse should be suspected when increasing tumor masses are present in distant sites outside of the thymic area. Conversely, if regrowth of lymphoma in other sites can be excluded, an isolated thymic mass after CTX likely represents RTH.

Background: Radiotherapy to the brain may produce endothelial damage to the vessels of the white matter resulting in hemorrhagic vasculopathy or true vascular malformations. Case Report: We report on two children with previous irradiation of the brain presenting with intracranial hemorrhage during follow-up of medulloblastoma and acute lymphatic leukemia respectively. Discussion and Conclusion: Development of cavernomatous malformations in patients who had radiotherapy of the brain is not unknown. Histopathological differential diagnosis between arteriovenous malformations, cavernomas and teleangieectasies may be difficult in these cases as well as differentiation from radiation induced hemorrhagic vasculopathy. MRI is adequate for detection of these lesions and may add to differential diagnosis. Intraläsionale Blutung und Massenblutung nach Schädelbestrahlung bei zwei jungen PatientenZusammenfassung Hintergrund: Die Bestrahlung des Schädels kann zu einer Schädigung des Endothels der Gefäße in der weißen Substanz führen mit der Folge einer hämorrhagischen Vaskulopathie oder von echten Gefäßmalformationen. Fallbericht: Es werden zwei Fälle vorgestellt mit intrakranieller Blutung nach früherer Schädelbestrahlung wegen Medulloblastom beziehungsweise akuter lymphatischer Leukämie. Diskussion und Schlussfolgerung: Die Entstehung von Kavernomen bei Patienten mit Schädelbestrahlung ist nicht unbekannt. Die histologische Differentialdiagnose zwischen arteriovenösen Malformationen, Kavernomen und Teleangiektasien kann in diesen Fällen schwierig sein ebenso wie die Differenzierung zu einer strahlenbedingten hämorrhagischen Vaskulopathie. Die MRT eignet sich zum Nachweis dieser Veränderungen und kann zur Differentialdiagnose beitragen. Schlüsselwörter: Schädelbestrahlung · Intrazerebrale Blutung · Kavernom · MRT

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