Introduction Ewing sarcoma is a rare malignant bone tumour that comprises approximately 10% of primary malignant bone tumours [1, 2]. It is the second commonest malig- nant bone tumour in children and occurs most fre- quently in the long bones and flat bones. It has a male preponderance. The commonest head and neck sarcoma is rhabdomyosarcoma; primary cranial Ewing sarcoma is rare and has been reported to occur with an incidence between 1 and 6% [3]. The commonest site of primary cranial Ewing sarcoma is the temporal bone [1, 4–6], followed by frontal, parietal and occipital bones. Sphe- noid [7, 8] and ethmoid bones are less commonly involved. Our literature search has revealed 52 cases of primary cranial Ewing sarcoma. The majority are case reports imaged with CT and the largest series contains 14 patients [1]. We describe three cases of primary cranial Ewing sarcoma with particular reference to the CT and MRI features. Case reports Case 1 A 7-year-old boy presented to his local hospital with a 3-week history of progressive headache, worse in the morning, vomiting, blurred vision and ataxia. On examination, he was slightly drowsy and had nystagmus on right lateral gaze. Papilloedema was seen on fundoscopy, but the examination was otherwise unremarkable. Wai-Yung Li Penelope Brock Dawn E. Saunders Imaging characteristics of primary cranial Ewing sarcoma Received: 4 October 2004 Revised: 27 December 2004 Accepted: 28 December 2004 Published online: 7 April 2005 Ó Springer-Verlag 2005 Abstract Background: Ewing sar- coma accounts for 10–15% of all childhood malignant bone tumours and is second in prevalence to oste- osarcoma. The skull bones are an unusual site of origin of primary Ewing sarcoma in children. Previous reports concentrate on the neuro- surgical aspects and relatively good outcome compared to other bone tumours of the calvarium. Reported cases mainly describe the imaging characteristics on CT. Objective: To describe the MRI and CT features of primary cranial Ewing sarcoma. Materials and methods: The neuroi- maging of three cases of primary cranial Ewing sarcoma are reviewed. Results: Our three cases show an extra-axial mass that is high attenu- ation on CT and low signal on T2- weighted MRI. Haemorrhagic com- ponents, dural extension and con- trast enhancement are also characteristic features. Conclusion: CT attenuation and magnetic reso- nance signal characteristics reflect sheets of densely packed cells seen in Ewing sarcoma. Keywords Skull Æ Tumour Æ Ewing sarcoma Æ CT Æ MRI Æ Children Pediatr Radiol (2005) 35: 612–618 DOI 10.1007/s00247-005-1438-2 ORIGINAL ARTICLE W.-Y. Li (&) Æ D. E. Saunders Departments of Radiology, Great Ormond Street Hospital for Children, Great Ormond Street, London, WC1N 3JH, UK E-mail: wyli@btinternet.com Tel.: +44-795-6955680 P. Brock Departments of Oncology, Great Ormond Street Hospital for Children, London, WC1N 3JH, UK