Macrocephaly UMLS:C4255213 Macrocephalus HP:0200135 Increased size of cranium Large skull UMLS:C4083076 Occipitofrontal (head) circumference greater than 97th centile compared to appropriate, age matched, sex-matched normal standards. Alternatively, a apparently increased size of the cranium. UMLS:C4280664 UMLS:C4280663 Large head Megacephaly Fyler:4335 Large calvaria Macrocephaly can be due to hydrocephalus (increased CFSF), megalencephaly (increased brain volume) or thickening of the skull. 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. [2007]], others by standard deviations [Farkas, [1981]]. It is important to add an indication of how far above the normal standard the head circumference is if an accurate assessment of this can be made. Macrocephaly is an absolute term. The term relative macrocephaly can be used when the head size centile exceeds the centile for height, for example, head size at the 75th centile with height at the 5th centile for age and sex. HP:0005496 Increased size of skull Big calvaria Big head HP:0005491 Increased size of head Large cranium HP:0000256 Macrocrania Big cranium Big skull Large head circumference Increased head circumference