Glioblastoma brain tumour. Coloured 3-D computed tomography brain scan showing a large glioblastoma (blue), a malignant tumour derived from supportive tissue in the brain. Image processing techniques have been used to cut away part of the skull. The red areas are the fluid-filled ventricles in the centre of the brain. Brain tumours damage surrounding tissue as they grow and increase the pressure in the skull, causing a variety of symptoms. These can include headache, vomiting, muscle weakness, loss of vision, speech difficulty, deterioration of mental function and epileptic seizures. Most cases of malignant brain tumour are fatal.