General Discussion

Subtle variations in the size and shape of a child’s face and head may be difficult to detect, and variations may be the result of normal differences. However, on occasion, these variances can be the result of an underlying pathologic process. It is in these instances that early detection can prompt interventions that can both allay parental anxiety and limit morbidity.

What constitutes a normal head size is based on statistical renderings of morphology. Abnormalities detected more easily by routine screening, measurement, and plotting on graphs that are widely available. Accurate measurement of the occiputofrontal circumference (OFC) is crucial in this regard. Abnormal head or face shapes may vary from the very subtle to the dramatic. Without direct familiarity of the more common syndromes that cause these abnormalities, a health care provider might detect that some abnormality exists without being able to articulate or pinpoint exactly what is outside the norm. Morphologic nomenclature is outlined in Table 2-1.

Table 2-1 Morphologic Nomenclature in Common Usage

(From Mooney PM, Siegel MI. Understanding Craniofacial Anomalies. New York: Wiley-Liss, 2002:12, with permission.)

An understanding of how the skull develops in relation to the bone structure’s response to brain structure is vital to this topic. Both genetic and environmental factors strongly influence this interplay. As the neonatal and infant brain greatly expands during normal neurodevelopment, the skull acts as an ever-changing and vital protective structure. Abnormalities of brain development or abnormalities of bony expansion are the primary reasons for abnormal head size and shape.

Although the causes of more serious abnormalities require early detection and intervention, even the more benign and common causes can benefit from treatment.

Plagiocephaly (a deformational abnormality of the skull) needs to be recognized as separate from craniosynostosis (premature fusion of growth plates) and abnormalities of brain development. Distinguishing between these entities can be a challenge, but several key features of each are vital to the provider.

Craniosynostosis, the premature fusion of one or more of the cranial sutures, can occur as part of a syndrome or as an isolated defect. Craniosynostosis is called “simple” when only one suture is involved and “compound” when two or more sutures are involved. Craniosynostosis is most commonly present at birth but is not always diagnosed when mild. Usually it is diagnosed as a cranial deformity in the first few months of life.

It is important to differentiate lambdoid synostosis from deformational plagiocephaly, which results from local pressure on a specific region of the skull, typically in one occipital region. The number of infants with deformational plagiocephaly has increased, partly as a result of the “Back to Sleep” campaign. The diagnosis of deformational plagiocephaly can be made clinically by viewing the infant’s head from the top. The differences between deformational plagiocephaly and craniosynostosis are outlined in Figure 2-1. The diagnosis of deformational plagiocephaly is made when the deformations noted in Figure 2-2 are present in an infant who had a typically round head at birth but, a few weeks or months later, the parents notice deformation of head shape.

Figure 2-1 Major cranial sutures and fontanelles.

(From Texas Pediatric Surgical Associates, Houston, Texas, with permission.)

Figure 2-2 Differences between positional plagiocephaly (A) and unilamdoid synostosis (B).

(From Gruss JS, Ellenbogen RG, Whelan MF. Lambdoid synostosis and posterior plagiocephaly. In: Lin KY, Ogle RC, Jane JA, eds. Craniofacial Surgery: Science and Surgical Technique. Philadelphia: WB Saunders; 2002:242.)

Medications Associated with Abnormal Head Size and Shape (In Utero Exposure)

Causes of Abnormal Head Size and Shape

Microcephaly (OFC <5%)

Macrocephaly (OFC >95%)

Abnormal Head Shape

Key Historical Features

Key Physical Findings

Suggested Work-up

Additional Work-up