Neurotoxic effects of lead in the chick embryo: morphologic studies

When lead salts are administered to 4 day old chick embryos in the appropriate doses, many of the surviving animals begin to form a large cyst at the back of the head by about the 9th day. Morphologic examination of such a cyst reveals that it consists of massive distension of the subarachnoid space in broad communication with the 4th ventricle. The cysts are probably caused by severe hemorrhage due to injury to the developing blood vessels in the central nervous system of younger embryos. The results indicate that lead exposure in young, developing animals causes hemorrhage in the central nervous system which results in permanent brain damage.