has part has part characteristic of has modifier Abnormality of skull size Decreased head circumference Although HC measures skull size, it typically also reflects overall brain volume and has been described as a widely used proxy of neural growth and brain size. Brain size outside of normal values is an important risk factor for cognitive and motor delay. Microcephaly at birth has been termed primary microcephaly and that acquired after birth is secondary microcephaly. abnormal decreased circumference head