Objective: Occipito-frontal (head) circumference (OFC) less than 3rd centile compared to appropriate, age matched, normal standards
Subjective: Apparently decreased size of the cranium
Head circumference is measured from just above the glabella (the most prominent point on the frontal bone above the root of the nose) to the most posterior prominent point of the occipital bone using a tape measure. Some standard charts are organized by centiles [Hall et al., ], others by standard deviations [Farkas, ]. It is important to add an indication of how far below the normal standard the head circumference is if an accurate assessment of this can be made. Microcephaly is an absolute term. The term relative microcephaly can be used when the head size centile is less than the centile for height, for example, head size at the 3rd centile with height at the 75% for age and sex.