premature closure of one or more cranial sutures during 1st 18-20 months of life, head misshapen; males affected 2x more than females, in the absence of adequate sutures brain growth may exceed space & compression can cause neurologic dysfunction from brain damage after 6 mo of age, can be associated w/ gene mutations/chromosomal alterations, premature closure of sagittal suture most common form (elongation of skull in a/p direction)