Leptomeningitis can be due to a variety of organisms, the commonest of which is meningococcus. A purulent inflammatory infiltrates can be seen filling up the subarachnoid space and the cerebral sulci. Meningitis leads to sepsis, edema and vascular spasm. The latter can lead to extensive cerebral hypoxia. Healed meningitis leads to organization and fibrosis of the basal cisterns and subsequent development of hydrocephalus.