Case Report Figure 1. FSE T2-weighted image, transverse plane: hemorrhage inside the posterior horn of the right lateral ventricle. Histopathological examination showed ependymoma grade II- ependymoma partim clarocellulare WHO G II. The operation was complicated by an epidural abscess at the site of craniotomy. It was treated surgically by remov- al of an osseous flap and implantation of a temporal epi- dural drainage. Further treatment was conducted at the Department of Oncology, where the patient received 4 courses of chemotherapy, and then, from December 2007 to January 2008, a two-phase radiotherapy of the whole CNS: in the first phase it was 2505 cGy/t in 15 fraction doses, in the second phase: 5385 cGy/t destined for the postoperative field and a higher dose – of 4000 cGy/t – for the Th8-S3 spi- nal canal. After a completed radiotherapy, seven courses of maintenance chemotherapy were introduced according to the Packer regimen. During the comprehensive treatment, the child was sub- jected to routine follow-ups at the MRI Laboratory, with an aim to have the efficacy of the introduced treatment assessed. The examinations were performed with the use of a 1.5T scanner and a 8-channel head probe, in three planes, T2- and T1-weighted images, and two phases. They found an extensive postoperative field reaching the left lateral ventricle and a large fluid collection surrounding the left hemisphere. For further diagnostics, SWI sequence with the following parameters was used: bandwidth: 90 Hz/Px, TR/TE: 58.0/44.1 ms, FOV: 230×230 mm, matrix: 320×320, GRAPPA 3, section thickness: 1.6 mm, gap: 20%, flip angle: 19, number of averages: 1, voxel: 0.7×0.7×1.6, acquisition time: 7 min. In a subsequent routine MRI examination carried out 19 months after the surgical procedure, the TSE T2-weighted 48 © Pol J Radiol, 2010; 75(3): 47-50 images showed a decreased signal intensity on the surface of the medulla oblongata and part of the cerebral hemi- spheres, as well as a chronic hematoma in the right ven- tricle. Figure 1. SWI sequence showed it more precisely and extensively: linear, non-signal producing lesions on the surface of the cerebellum, brain, medulla oblongata, and along the ependyma of the ventricles of the ventricular sys- tem; in the right occipital horn – a chronic hematoma with fluid. Figure 2A–C. Basing on that, a postoperative hemo- siderosis of the brain was diagnosed. In February 2009, a further neurosurgical operation was performed. It was meant to fill the extensive bone defect in the cranial vault with an artificial material (cranioplasty). Discussion Cerebral hemosiderosis is nowadays a very rare late com- plication of extensive neurosurgical procedures. It is mostly connected with anatomical hemispherectomy (sur- gical method of hemisphere removal, saving basal gan- glia). Anatomical hemispherectomy as a technique of brain tumor treatment was first published in 1928 – a procedure of glioma resection conducted and described by Walter Dandy [2]. In the following years, this technique was mostly used in patients with epileptic seizures, resistant to pharmacotherapy. The following early postoperative complications were reported: aseptic meningitis connected with the passage of products of blood lysis to the cerebro- spinal fluid, dislocation of the remaining part of the brain and its herniation towards the postoperative hole, as well as hydrocephalus. The next years witnessed quite frequent (i.e. in 33% of cases) serious late postoperative complica- tions in the form of superficial hemosiderosis of the brain, as well as spontaneous and traumatic hematomas [3,4]. The formation of hematomas is promoted by an ‘empty’ space left after anatomical hemispherectomy. Hydrocephalus and hemosiderosis of the brain were the main complications and the cause of death in those patients. Pathomechanism of hemosiderosis is not fully understood. It is believed that the direct cause of this complication is bleeding (superficial subarachnoid and intraventricular) connected with enormous distortions of normal anatomical relations of the brain – ‘the empty space’ after the resected hemisphere [5]. With long-lasting or recurrent subarach- noid hemorrhages, hemosiderin is deposited on the surface of the brain, cerebellum, spinal cord and cranial nerves. Frequent complications include deafness, ataxia and smell disturbances [6]. A typical location of those lesions is the surface of the brain stem and cerebellar hemispheres. Histopathological examinations tend to show depos- its of hemosiderin covering the surface of the brain and the ependyma of the ventricles, i.e. regions remaining in a direct contact with the cerebrospinal fluid. They cause gliosis, neuronal loss and demyelination. Two types of glial cells take part in the process of hemosiderin deposition: microglia, synthesizing ferritin, and Bergman’s glial cells, which are the source of iron and also take part in synthe- sizing ferritin [7,8]. In the literature, there are reports on cases of hemosidero- sis caused not only by anatomical hemispherectomy, but also by brain tumors, e.g. ependymomas or astrocytomas