I think brain defect is a conceptual mistake, which should be skull defect. It refers to the lack of a part of the skull after operation, mainly referring to the part covering the brain.

Deformities are mainly congenital developmental problems, such as pointed skull malformation and congenital cerebellar dysplasia, and most of them are accompanied by mental retardation.

You obviously don't belong to any of the above situations. If there is a lump, it means that the skull is not healing well. It doesn't matter, the civil service exam is not restricted.