Revisiting the Cephalic Index: The Origin, Purpose, and Current Applicability—A Narrative Review

Abstract

Introduction Cephalometry is the measurement and study of the proportions of the head and face, and infant skull deformities have been the subject of many clinical studies over the last 30 years. Clinical protocols to document change are especially critical during periods of growth and development, but reference values and norms are lacking for infants, especially in the first year after birth. Discussion Key publications were reviewed by the authors to provide a narrative review of the 1) origin of the cephalic index (CI), 2) adaptations of the measure over time, 3) anatomical landmarks and alignments used, 4) clinical tools, 5) necessary considerations for different ethnic, sex, and cultural influences, 6) value and limitations of CI measurements, and 7) appropriate use of the CI in the documentation of infant skull deformities. The CI calculation has remained constant since the 1840s, although the cranial shape classifications have changed many times over the years. Conclusions Used in isolation, the two-dimensional (2D) and linear nature of the CI fails to describe the magnitude of the three-dimensional (3D) head deformity. However, the CI can and should be used in conjunction with other 2D and 3D measurements to provide a more detailed description and understanding of the entire cranial deformity. For today's cranial clinicians and allied health care professionals, the commonly referenced CI chart fails to reflect 1) the natural skull changes noted with supine sleeping infants, and 2) the cultural diversity of the infant population currently treated. Although the CI provides information about one of the most obvious features of the dysmorphology, clinicians must also document and report other distinct features such as frontal flattening or bossing, parietal shape or involvement, sloping, displacement, and/or posterior asymmetry. Clinical Relevance The CI should be used in conjunction with other 2D and 3D anthropometric measurements to provide a more detailed assessment of the entire cranial deformity. The CI results should be discussed with the medical team along with a complete review of other 2D and 3D measurements to determine the best course of action for orthotic treatment or nontreatment of the head shape.