Impacting Infant Head Shapes

Pat Hummel, RNC, MA, NNP, PNP; Dana Fortado, OTRL

Disclosures

Adv Neonatal Care. 2005;5(6):329-340. 

In This Article

Classifying Cranial Dysmorphology

An infant presenting with an abnormal head shape requires careful investigation. The etiology of cranial dysmorphology can be divided into 3 categories that include:[6]

  • Malformations

  • Deformations

  • Disruptions

The earliest or primary defect in morphogenesis determines which category is appropriate.

Malformations occur in the first 8 weeks of pregnancy during embryogenesis. Malformations may be caused by either a genetic or environmental etiology, or with a combination of both. Deformations occur after embryogenesis, and result from nondisruptive mechanical forces, such as intrauterine or postnatal positioning, that cause abnormal formations or distortions of normal body parts. Disruptions result from a destructive process that occurs after normal organ formation.

Malformations, deformations, and disruptions can result in consistent patterns of multiple anomalies, which are then further classified as either syndromes or sequences. A sequence is a pattern of multiple abnormalities resulting from a cascade of apparently unrelated consequences that proceed from a single defect (e.g., Pierre Robin sequence). A syndrome is a collection of multiple anomalies that occur in a consistent pattern and result from a common pathogenic genetic etiology (e.g., Down syndrome, Apert's syndrome).[7] Abnormal head shapes may be associated with either a sequence or a syndrome, or be an isolated finding.[6,8] Table 1 defines common nomenclature used in describing head shapes, along with the suture line often involved with craniosynostosis.

The term plagiocephaly is a Greek derivative and means oblique head. It is a nonspecific term used to denote an asymmetric head; however, it does not denote a specific head shape or the etiology of the problem and therefore can be applied to all infants with an abnormal head shape, regardless of the etiology.

Positional plagiocephaly, also called deformational plagiocephaly or plagiocephaly without synostosis, is an acquired phenomenon that has become more common since the 1990s "Back-to-Sleep" initiative to prevent sudden infant death syndrome (SIDS).[9,10,11] In 1992, 70% of infants were prone sleeping and plagiocephaly rates were 1 in 300 live births. In 1997, 5 years after the "Back-to-Sleep" campaign was initiated, prone infant sleeping position decreased to 10.5%; concurrently the plagiocephaly rate rose 5-fold, to 1 in 60 live births.[12,13] Although prone sleeping appears to have a protective effect against positional plagiocephaly, this benefit is obviously outweighed by the lives saved with the reduction in SIDS rates associated with supine sleep positioning.

Positional plagiocephaly in the supine sleeping infant usually involves a flattened occiput. Occipital flattening may be asymmetric; this suggests a positional preference where the infant preferentially turns his/her head to one side. A positional preference may be secondary to, or a precursor of, torticollis.

Limited neck mobility, as seen in infants with Klippel-Feil sequence, may also result in excessive brachycephaly. Conditions associated with skull demineralization, such as osteogenesis imperfecta, or hypophosphatasia, can lead to severe deformational brachycephaly due to cranial demineralization.[10]

Positional plagiocephaly is more common in infants from multiple gestation pregnancies. The infant in the lower uterine segment is more susceptible, likely because of the more restrictive intrauterine environment in the last trimester.[14] Infants with hydrocephalus are also at increased risk of plagiocephaly secondary to preoperative and poserative changes in cranial volume and corresponding shifts in bones and sutures. Positioning limitations imposed by drainage devices or shunts contribute further to the development of plagiocephaly.

A 2-year study of the natural course of positional plagiocephaly found that the severity increased and peaked at 4 months of life and then improved over time. Most cases resolved clinically by 2 years of age. Limited head rotation, lower activity levels, and supine sleep position were important deterrents to improvement.[15]

Torticollis, also called wryneck, is the clinical term for a twisted or rotated neck. Torticollis may be congenital or acquired. Pathologically, fibrous shortening of the sternocleidomastoid (SCM) muscle is noted. Congenital torticollis is caused by muscular or neurological factors, or by bony abnormalities of the cervical spine. Congenital muscular torticollis, has an estimated incidence of < 2% and occurs more often in infants with a history of breech presentation.[16] The etiology of torticollis is not known; however, it is associated with intrauterine and perinatal events such as malposition of the head in utero and injury to the SCM muscle and subsequent fibrosis. It is also associated with multiple gestations. Although acquired and congenital torticollis have the same clinical presentation, the timing of presentation differentiates the two. Acquired torticollis may result from a benign myositis, or a more life threatening cause such as vertebral subluxation or retropharyngeal abscess.[17] Recently, with the increased incidence of plagiocephaly, a concurrent increase in torticollis rates has also been identified. Although torticollis may precede plagiocephaly by limiting head movement and rotation, torticollis appears to develop secondary to plagiocephaly in a large proportion of cases.[18] Infants with torticollis have restricted range of motion of the neck, with the head tilted toward the shortened SCM muscle; the chin is usually, however not always, rotated to the opposite side. Limited range of motion may result in plagiocephaly and facial scoliosis.[19,20]

An infant presenting with positional plagiocephaly and asymmetric occipital flattening, should be carefully evaluated for torticollis, which may be the precursor to the plagiocephaly. Conversely, severe plagiocephaly with persistent head positioning to one side may lead to torticollis.[18,19] An early preferential head orientation may indicate the presence of neck muscle dysfunction. Early identification and intervention may help prevent the development or progression of positional plagiocephaly and torticollis.[20]

Dolichocephaly is a term used to describe a tall, narrow head. Dolichocephalic head shapes are relatively rare in cultures where infants sleep supine.[5] An exception to this is the preterm infant, who has historically retained a dolichocephalic head shape due to extended periods of prone or side-lying positioning in the NICU. Although long-term changes in preterm infant head shape have not been systematically studied, a reduction in dolichocephaly is expected with the transition to supine positioning before and after hospital discharge. Preterm infants with pronounced dolichocephaly have historically been judged as less attractive.[21] These differences may now be judged even more abnormal since brachycephaly has become the American norm.

Extreme dolichocephaly may indicate sagittal suture synostosis. This can usually be differentiated by the severity of the head narrowing, lack of improvement over time in supine positioning, and extreme frontal bossing and occipital protuberance.[1]

Craniosynostosis, or premature fusion of one or more cranial sutures, is usually a malformation, originating early in the pregnancy, and can be influenced by genetic or environmental factors. Some cases of craniosynostosis are deformational, related to constraint of the fetus, such as abnormal positioning in utero, fetal overcrowding in multiple pregnancy, oligohydramnios, and increased duration of the first stage of labor, all leading to fetal head constraint.[2,6]

Craniosynostosis may involve one or all of the sutures. Head and brain growth are restricted and head shape is abnormal when all of the sutures are fused. If some but not all of the sutures are fused, head circumference and brain growth remain normal; however, the head shape is altered.

Craniosynostosis is surgically correctable. If all of the sutures are involved, the goal is normal brain growth and cosmetic improvement; if not all sutures are involved, the goal is cosmetic improvement only. The importance of cosmetic improvement should not be minimized; long-term outcomes are enhanced both with normal brain growth and improved appearance.[1,2]

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