<unk>  is a neurological disorder in which the circumference of the head is at least three standard deviations smaller than average for the person's age and sex.<unk>  may be congenital or it may develop in the first few years of life.
Microcephaly
Acephaly 
Plagiocephaly
Macrocephaly
Deformational plagiocephaly
Acrania
Megalencephaly
Hydranencephaly