A 1-year-old girl with HLH with CNS involvement (patient 8). a Axial postcontrast T1-W image shows multiple small nodular or ring-enhancing parenchymal lesions in both cerebral hemispheres. Mild leptomeningeal enhancement is also apparent. b Axial T2-W image at the same level reveals a characteristic laminated pattern (hyperintense centre and hypointense peripheral rim) of nodular parenchymal lesions with variable degrees of perilesional oedema. c Follow-up axial T2-W image 6 months later demonstrates progression of the disease with confluent parenchymal lesions. d Axial ADC map demonstrates restricted water diffusion in nodular parenchymal lesions (arrows) and increased water diffusion of other portions of the confluent lesions

A 3-month-old boy with HLH with CNS involvement (patient 9). a Coronal postcontrast T1-W image with fat suppression reveals small nodular enhancing lesions (arrows) in the right side of the midbrain and pons. b, c Compared to axial postcontrast T1-W image with fat suppression (b), diffuse leptomeningeal enhancement is more conspicuous on postcontrast FLAIR image (c). There are multiple nodular lesions in both thalami. d Follow-up axial postcontrast FLAIR image at the same level demonstrates complete disappearance of diffuse leptomeningeal enhancement. Clinical manifestations were also improved at that time

An 18-month-old boy with HLH with CNS involvement (patient 5). a, b Axial precontrast CT image (a) and axial T2-W image (b) show confluent parenchymal lesions mainly in both parietal lobes. c Axial precontrast T1-W image reveals T1 shortened bands along the cortical grey matter in the lesions, suggesting cortical laminar necrosis. d Proton MR spectroscopy demonstrates a small lactate peak (L) and elevated glutamine/glutamate complex (arrow). NAAN-acetylaspartate, Cr creatine, Cho choline

A 3-year-old girl with HLH with CNS involvement (patient 7). a Axial T2-W image shows mild ventriculomegaly and diffuse sulcal dilatation, suggesting communicating hydrocephalus. There is no focal or diffuse brain parenchymal lesion. b Follow-up axial T2-W image at the same level reveals normalization of the communicating hydrocephalus

A 1-year-old boy with HLH with CNS involvement (patient 10). Axial precontrast CT image shows diffuse brain swelling without a focal lesion. He showed a fatal course of the disease and died of brain herniation