Brachycephaly


Continuing Education Activity

Brachycephaly is an infant skull deformity characterized by a shortened anteroposterior skull length and a widened biparietal diameter. This condition may be non-synostotic (positional) or synostotic (craniosynostosis). Accurate diagnosis of the type of brachycephaly is paramount in deciding the appropriate treatment options. This activity reviews the evaluation and management options for brachycephaly. It also highlights the role of the interprofessional team in evaluating and managing this condition.

Objectives:

  • Describe the etiology of positional brachycephaly.
  • Summarize the pathophysiology of synostotic brachycephaly.
  • Identify the indication for neck physiotherapy in infants with brachycephaly.
  • Outline the importance of interprofessional team coordination when managing patients who present with brachycephaly.

Introduction

The term "brachycephaly" is derived from the Greek words "brakhu" (short) and "cephalos" (head), meaning "short head." Brachycephaly is an infant skull deformity characterized by a lower than normal ratio of the skull's length to its width.[1] Infants with this form of skull deformity have a flattening of the cranium's occipital aspect; consequently, there is an apparent shortening of the skull in the anteroposterior dimension (length).[2] Brachycephaly may be positional (non-synostotic) or synostotic. The incidence of infant positional skull deformities has been on the rise since 1992. This appears to be related to the introduction of the measure of infant supine sleep positioning by the American Association of Pediatrics as a means to prevent sudden infant death syndrome (SIDS).[3][4] However, brachycephaly in infants can also occur due to the phenomenon of craniosynostosis.

The skull in infants has the dual function of providing protection for the brain and allowing for its volumetric growth and development. The cranial vault or calvaria in infants comprises several bones separated by fibrous joints or cranial sutures. There are two frontal bones separated by a metopic suture and two parietal bones separated from each other by a sagittal suture. The two parietal bones are separated from the two frontal bones by a coronal suture (anterior fontanelle; the future Bregma). Paired squamosal sutures separate paired temporal bones on either side of the calvaria from the two parietal bones, and a lambdoid suture (posterior fontanelle; future lambda) separates a single occipital bone from the two parietal bones. Craniosynostosis refers to the premature mineralization and fusion of one or more of these fibrous joints, which occur between the bones of the calvaria before the completion of brain growth and development in infants.

Etiology

Positional (non-synostotic)/ Deformational Brachycephaly

The cranial sutures or fibrous joints that separate the cranium bones do not fuse or ossify at birth. This ensures the essential event of volumetric growth and development of the brain postnatally. As a result, a new-born skull retains its ability to mold in the initial months of life and is, therefore, susceptible to the deformational effects of external force. The frequent practice of placing an infant in a supine sleeping position can lead to a symmetrical flattening of the occipital bone resulting in positional or deformational brachycephaly.[5] 

A unilateral flattening of the occipital bone in infants may result in deformational plagiocephaly, a related positional skull deformity. Positional brachycephaly may also be observed at the time of birth in some infants. This may be attributable to intrauterine fetal head constraining factors such as multiple gestations, oligohydramnios, and congenital or acquired structural anomalies of the uterus.

Brachycephaly Due to Craniosynostosis (Synostotic Brachycephaly)

The skull consists of the neurocranium and the viscerocranium (also known as splanchnocranium). The neurocranium forms a protective shell surrounding the brain and the brain stem, while the facial bones form the viscerocranium (or facial skeleton). The neurocranium consists of the cranial vault (calvaria) and the chondrocranium (skull base). The bones that constitute the chondrocranium mineralize by endochondral ossification, which is the replacement of cartilage by the bone matrix. The bones of the calvaria are established by intramembranous ossification, which involves direct mineralization of mesenchymal connective tissue without the need for a transitional cartilaginous component.

As alluded to above, premature abnormal mineralization of the cranial sutures, which can occur between the calvaria bones, results in craniosynostosis. Bilateral premature mineralization of the coronal sutures leads to bicoronal synostosis called brachycephaly.[6] Unilateral premature mineralization of the coronal suture in infants results in anterior plagiocephaly, a related skull deformity. Genetic abnormalities such as Fibroblast Growth Factor Receptor type 2 (FGFR-2)FGFR-3, twist homologue-1 (TWIST1), and ephrin-B1 (EFNB1) gene mutations may predispose an infant to craniosynostosis. These mutations may be clinically syndromic or non-syndromic.[6] Clinical syndromes with craniosynostosis include Crouzon syndrome, Apert syndrome, Pfeiffer syndrome, Saethre-Chotzen syndrome, Antley-Bixler syndrome, and Muenke syndromes.

Epidemiology

Positional brachycephaly and/or plagiocephaly is the most common head shape abnormality in infants, affecting between 20% and 50% of infants in the United States.[1][7][8] 20% of cases may be observed at the time of birth, while 80% of the cases present within the first three months of life as an acquired postnatal cranial deformation.[9] Positional brachycephaly and/ or plagiocephaly is also more common in male children, and up to 20% of infants with positional cranial anomalies have some degree of torticollis.[9] Synostotic brachycephaly, resulting from bicoronal synostosis, occurs in around 3% of non-syndromic synostoses.[10] and has a higher prevalence of around 0.5 per 10000 live births in syndromic synostosis.[11]

History and Physical

It is essential to differentiate between non-synostotic (brachycephaly and/ or plagiocephaly) and synostotic (bicoronal and/ or bilambdoid synostosis) infant head shape abnormalities by taking a detailed history. Important questions include:

  • Family history of abnormal head shapes
  • Prenatal exposure to teratogens
  • Noting when the abnormality was first observed
  • History of intrauterine fetal head constraints
  • Birth history
  • The degree or severity of the abnormality.

Physical examination should include measurement of the infant's head circumference, palpation of the sutures for evidence of ridging, and examining the fontanelles for assessment of elevated intracranial pressure. Anthropometric measurements using cranial calipers provide vital information on head length, width, and occipitofrontal transcranial diameters. The infant's head should be assessed from the anterior view, posterior view, lateral view, and importantly from the vertex (top of the head).

A complete neurological examination should also be performed. Indices such as the cephalic index (i.e. the ratio of maximum width to the maximum length of the skull) and the cranial vault asymmetry index (i.e. the percentage difference between the diagonal dimensions of the skull) may provide useful information on the degree of severity of an infant's head shape abnormality.

Positional brachycephaly is characterized by bilateral/ symmetrical flattening of the occiput, widening of the posterior skull, bilateral temporal bossing, and a round face. There is usually evidence of sutural ridging (bicoronal and/or bilambdoid synostosis) with synostotic brachycephaly. Bicoronal synostosis is often associated with turricephaly; the forehead appears somewhat towered with seemingly shallow orbits and a shortened nasal bone. Indeed, some infants with bicoronal synostosis resulting in brachycephaly have Harlequin orbits and exophthalmos.[6] During the physical examination, it is important to determine whether or not there are other features present, which may indicate the presence of an associated syndrome.[12] It is also essential to determine whether urgent or elective treatment is required.[12]

Evaluation

The diagnosis of positional (non-synostotic) brachycephaly and/ or plagiocephaly is almost always made clinically by history and appropriate physical examination. Radiological imaging studies are usually not required.

Conversely, synostotic infant head shape abnormalities require radiographic evaluation of the abnormal sutures. Computed tomography (CT) scan with three-dimensional image reconstruction is the imaging modality of choice. Other imaging modalities such as ultrasonography and magnetic resonance imaging (MRI) may also be employed. In synostotic brachycephaly (bicoronal synostosis), CT scan imaging studies usually demonstrates a thickening of the sutures implicated. In some instances, there may be non-visualization of these sutures. Genetic tests may be undertaken if affected infants present with additional features suggesting the presence of associated syndromes.

Treatment / Management

Positional (non-synostotic) brachycephaly and/ or plagiocephaly is usually treated conservatively. Surgery is not indicated, given the absence of craniosynostosis. The parents of affected infants should be reassured, and attempts may be made to alternate the infant's head position for sleep (repositioning education). Other conservative treatment measures include massage therapy, physiotherapy (for torticollis), assistive devices, and helmet therapy.

Synostotic infant head shape abnormalities require surgical intervention, with the timing of surgery being crucial. Infants with signs or symptoms of raised intracranial pressure require urgent interventions. Surgical repair of uncomplicated bicoronal synostosis is usually delayed until after the sixth month of life and is usually undertaken between the sixth and tenth months of life. Lambdoid synostosis should be repaired earlier, between the second and sixth months of life. Established surgical management strategies include sub-total or complete calvarial vault remodeling, cranioplasty (spring-assisted), and endoscopic suturectomy with postoperative helmet therapy. Early referral is advised as delayed referrals may result in more extensive surgical interventions with higher risks of complications.

Differential Diagnosis

Synostotic (bicoronal and/or bilambdoid synostosis) brachycephaly in infants may be associated with multiple syndromic conditions. It is therefore essential to follow a standardized pattern of physical examination to avoid overlooking any vital etiological clues. Some of the common syndromes included in the differential diagnosis are as follows:

  • Crouzon syndrome: Bicoronal synostosis resulting in brachycephaly, exorbitism, hypoplasia of the midface with a characteristic underbite (mal-occlusion), and an upturned nose.
  • Apert syndrome: Bicoronal synostosis with syndactyly. 
  • Pfeiffer syndrome: Craniosynostosis, abnormally broad and medially deviated thumbs and great toes, protruding eyes, and conductive hearing loss
    • Type 1: Turribrachycephaly, midface hypoplasia, high forehead, ocular hypertelorism, hypoplastic maxilla, and dental abnormalities. Intelligence is usually normal.
    • Type 2: Cloverleaf skull (or Kleeblattschadel type craniosynostosis), hydrocephalus, ocular proptosis, beak-shaped nose, and neurological problems due to severe involvement of the brain
    • Type 3: Same as type 2 except for the absence of Cloverleaf skull. Additionally, there is a presence of natal teeth and anterior cranial base.
  • Saethre-Chotzen syndrome: Also called "acrocephalosyndactyly". Craniosynostosis and or syndactyly of certain digits
  • Carpenter syndrome: Craniosynostosis, syndactyly of certain digits and/or polydactyly.
  • Antley-Bixler syndrome: Craniosynostosis, proptosis, low set ears, mid-face hypoplasia, radiohumeral or radioulnar synostosis, arachnodactyly, and joint contractures.
  • Muenke syndrome: Coronal craniosynostosis, carpal synostosis, hearing loss, developmental delay, Cone-shaped epiphysis, and High narrow palate.
  • Beare-Stevenson cutis gyrata syndrome: Craniosynostosis, cutis gyrata (furrowed and wrinkled appearance of skin and acanthosis nigricans), choanal atresia, abnormality of the pancreas, and aplasia/Hypoplasia of the earlobes.
  • Jackson-Weiss syndrome: Craniosynostosis, midfacial hypoplasia, broad great toes, and/or malformation or fusion of certain bones within the feet

Prognosis

Positional (non-synostotic) brachycephaly and/ or plagiocephaly are the most common infant head shape abnormalities encountered in the primary health care setting. Parental reassurance and management with conservative measures such as repositioning education are usually sufficient, with improvements evident in most infants as they attain their developmental milestones.[8] 

Refractory cases of positional brachycephaly should be referred for helmet therapy, and any suspicious cases of craniosynostosis should be referred early for an opinion from an experienced craniofacial team. Early craniofacial referrals of synostotic brachycephaly may obviate the need for more extensive surgical interventions.

Complications

Positional brachycephaly primarily raises aesthetic concerns. Reliable evidence on its effect on the neurological development of affected infants is lacking. Conversely, untreated synostotic brachycephaly may impede volumetric brain growth and development, is associated with elevated intracranial pressures (ICP) in infants, and has a high incidence of intracranial hypertension in older untreated patients.[13] 

Cognitive and behavioral difficulties in those affected have been previously suggested to have some relationship with elevated ICP.[6] However, no correlation was identified between both variables in a number of other studies.[14][15][16][15]

Consultations

A pediatrician usually diagnoses the condition of brachycephaly in infants. Specialist consultation with a craniofacial team traditionally led by a pediatric neurosurgeon is necessary in cases of synostotic brachycephaly.

Deterrence and Patient Education

Parents with concerns about the head shape of their infants should consult a pediatrician early. Further specialist consultation with a craniofacial team can be arranged by the pediatrician if there is suspicion for craniosynostosis.

Enhancing Healthcare Team Outcomes

Brachycephaly can be diagnosed by history and physical examination by primary care physicians or pediatricians. It is essential to distinguish between non-synostotic and synostotic brachycephaly. Most cases of non-synostotic brachycephaly improve with conservative measures. Refractory cases should be referred for consideration of helmet therapy. Cases of craniosynostosis should be referred early for craniofacial consultation and appropriate surgical management.


Article Details

Article Author

Michael Ita

Article Editor:

Munaza Batool Rizvi

Updated:

1/11/2021 3:53:31 PM

PubMed Link:

Brachycephaly

References

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