Malignant brain tumours remain a not uncommon cause of disability and premature death, particularly in children and middle-aged adults. This is only too weIl known by those con- cerned with the dinical management of such patients. Thus, not onlyare malignant cerebral gliomas very aggressive tumours, usually associated with a rapidly fatal outcome, but also it has been recognised more recently that low grade gliomas often have a poor prognosis. Furthermore, the increased application of non-invasive neuroradiological imaging to patients with other types of tumour has disdosed an even larger...