Macrophages in nervous system is known as:

Microglia are scavenger cells that resemble tissue macrophages and remove debris resulting from injury, infection, and disease (eg, multiple sclerosis, AIDS-related dementia, Parkinson disease, and Alzheimer disease). Microglia arise from macrophages outside of the nervous system and are physiologically and embryologically unrelated to other neural cell types. Ref: Ganong's Review of Medical Physiology 23rd edition, Chapter 4.