Head circumference: the forgotten tool for hydrocephalus management. A reference interval study in the Spanish population.

INTRODUCTION: In children, deviations from the normal range of head circumference (HC) have traditionally been related with CSF dynamics abnormalities. In adults, this neglected parameter is helpful in the diagnosis and understanding of the pathophysiology of some CSF abnormalities. It has been demonstrated that HC is related to height. Because humans have increased in stature dramatically during the last 50 years, pediatric charts for head growth physiology and normal HC values in adults should be reevaluated.
OBJECTIVES: The main aim of the present study was to assess HC in a series of 270 normal healthy Spanish adults and to determine any differences between sexes and age groups. A secondary aim was to discuss the relevance of this parameter in the management of hydrocephalus in adult people.
METHODS: HC measurements were taken using a measuring tape placed over the greatest frontal and occipital protuberances. The reference interval and the upper and lower thresholds for HC were calculated by 3 different methods: normal distribution, the non-parametrical percentile method, and the "robust method".
RESULTS: The results were consistent and showed that Spanish adult men with a HC greater than 60 cm, and Spanish adult women with a HC greater than 58 cm should be considered macrocephalic. Microcephaly should be considered when HC is 53.6 cm in men and 51.3 cm in women. Adult age groups of either sex do not present any statistically significant differences in HC.
CONCLUSIONS: HC obtained in Spanish adult people are greater than those reported in the classical Nellhaus graphs in both men and women aged 18. These findings should be considered in the management of hydrocephalus in adults today.