Macrocephaly is defined as head circumference greater than two standard deviations above the mean, or greater than the 97th percentile, for age, sex, race, and gestation. Macrocephaly affects more than 2- 3% of children. Some children with large head size have their measurement percentiles matched by height and weight, accompanied by normal neurological milestone progression. In other cases, the head size is accelerating out of proportion to the rest of the body and warrants neurosurgical evaluation.