<unk> , which literally means smooth brain, is a rare brain formation disorder characterized by the lack of normal convolutions (folds) in the brain. It is caused by defective neuronal migration, the process in which nerve cells move from their place of origin to their permanent location. It is a form of cephalic disorder.
The surface of a normal brain is formed by a complex series of folds and grooves. The folds are called gyri or convolutions, and the grooves are called sulci. In children with<unk> , the normal convolutions are absent or only partly formed, making the surface of the brain smooth.   Terms such as 'agyria' (no gyri) or 'pachygyria' (broad gyri) are used to describe the appearance of the surface of the brain.
Lissencephaly
Schizencephaly
Holoprosencephaly
Hydranencephaly
Megalencephaly
Anencephaly
Spina bifida
Deformational plagiocephaly