ABSTRACT
Primary tumours of the central nervous system (CNS) are classified and graded by the World Health Organization (WHO). WHO classifies primary tumours of the CNS into categories based on the cell or tissue of origin. Relative incidences of the various types of brain tumour vary between children and adults. In adults, metastases from non-CNS primary tumours account for 50 per cent of brain tumours. CNS metastases are uncommon in children; most brain tumours in children are primary CNS lesions with the most common forms as follows: astrocytoma of varying grade, medulloblastoma, ependymoma and craniopharyngioma. Multiple sclerosis is a chronic CNS disease of young adults characterized by the presence in the brain and spinal cord of focal lesions of demyelination, known as plaques. Haemorrhagic infarction refers to haemorrhage into a region of infarcted brain. Dementia should be differentiated clinically from delirium, psychiatric illness such as depression, and specific brain lesions leading to restricted function such as aphasia.
