Growth of Interorbital Distance and Skull Thickness as Observed in Roentgenographic Measurements

During the first two and one half decades of man's life a great many physical changes in size and shape occur. The growth of the head is one interesting facet of this overall development. This paper presents the group patterns of change through which two areas of the cranium-the thickness of the skull and the distance between the orbits-must pass to reach their adult size. In addition, the closure of the major cranial sutures will be discussed. Variations from the usual status of these three measurements are a part of certain pathological conditions. For example, skeletal variations are frequently associated with mental retardation, and the state of the cranial sutures with changes in intracranial pressure. Percentile standards based on the roentgenographic measurements of interorbital distance and skull thickness for a group of healthy children are presented as a reference of comparison with less healthy children. The progress of the healthy individual within the group is still to be determined. Although sampling shows that he may tend to hold the same position on the percentile standard this is not necessarily true. This project will be taken up in a subsequent publication. Material All the measurements are obtained from roentgenograms of the heads of healthy subjects from families of better-than-average economic circumstances in Denver. Radiographs of the skull and of the paranasal sinuses are used. The sinus films are taken on an angle board with nose and forehead touching the cassette and the roentgen-ray tube in the vertical position. The focal-film distance at the center of the cassette is 28 in. Skull films are obtained at a focal-film distance of 7 ft. in posteroanterior and lateral projections, with the child's head held immobile in a cephalostat as soon as he is old enough to tolerate it, usually by the three year-nine month visit. Lateral projections only, without the cephalostat, are taken of the infants and the younger preschool children. Sinus radiographs are obtained at six-month intervals, the skull radiographs, yearly. All measurements are determined and checked by the author with a Vernier caliper, and the scale is read to the nearest 0.01 cm. A number of reference points on the lateral projection of the skull have been used by earlier investigators to determine its thickness (1, 2). Lambda was chosen as the point most easily identified on films at all ages for the present study (Fig. 1). As is always true of skull roentgenograms, extraneous shadows cast by the normal irregularities of the inner surface of the skull may be a source of error. As nearly as it can be identified, the actual thickness of the skull in this area is recorded. As stated previously, these films are taken on a yearly basis between the half-birthday and the birthday, necessitating interpolation of the measurements to the desired ages for the purpose of setting up standards at six-month intervals.