A commentary on the growth of the human brain and skull.

Abstract

AbstractThis paper tests the suggestion put forth by Tanner ('55) and Eichorn and Bayley ('62) to the effect that the brain participates in the parapubertal spurt of growth which characterizes many of the dimensions of the human body. To this end, longitudinal data consisting of oriented head roentgenograms of 11 boys were examined. Two measurements were taken directly from each lateral head film: (1) skull length, measured from glabella to opisthocranion, and (2) endocranial length, the maximum length of the endocranial contour in the mid‐sagittal plane.While many of the individual cumulative curves depicting growth in skull length exhibit a parapubertal acceleration, all of the curves for endocranial length comprise segments of a parabolic arc representing a single decelerating phase of growth. Mean incremental curves, mathematically fitted, further emphasize the differences in velocity and pattern of size attainment for the two dimensions tested. The data here presented, then, fail to implicate the brain in the general spurt of growth evident for the external dimensions of the head at adolescence.It is suggested that two discrete systems are evident in the growth of the skull: a rapidly growing neural system essentially completed by adolescence, and a facial system of slower growth and longer duration. The conventional measurement of skull length cuts across both systems, appraising neural growth and the cerebral skeletal envelope prior to adolescence, and then superimposing the facial component, the forward projection of the frontal sinus, during adolescence and post‐adolescence.