Brain tumour. 3D diffusion tensor imaging (DTI) magnetic resonance imaging (MRI) scan of nerve pathways (coloured) in a brain with a tumour (red, centre left). The brain is seen from the side, with the front of the brain at left. Brain tumours can be benign or malignant (cancerous). They can cause seizures, headaches, and memory and personality changes due to the growth of the tumour. The nerve fibres include the corticospinal tract (blue), passing from the motor cortex to the spinal cord. Diffusion tensor imaging (tractography) measures the direction of water diffusion, which in the brain reveals the orientation of nerve fibres.