Surgery for Nonsyndromic Single-Suture Craniosynostosis

Updated: Jan 05, 2017
  • Author: John A Jane, Jr, MD; Chief Editor: Brian H Kopell, MD  more...
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Overview

Background

Craniosynostosis occurs in approximately 1 in 2000 live births. The term craniosynostosis refers to premature closure of one or more of the cranial vault sutures—namely, the metopic, sagittal, coronal, and lambdoid sutures. [1] (See the image below.) 

Normal anatomic suture configuration. Normal anatomic suture configuration.

Premature closure of a suture leads to characteristic changes in the shape of the skull, which relate not only to the reduced growth at the fused suture but also to the compensatory growth at adjacent open sutures. The resultant deformity is often observable in the neonatal period, but milder forms may not be immediately apparent. Most cases of craniosynostosis involve a single suture, occur sporadically without a prior family history of craniosynostosis, and are not associated with other physical abnormalities (ie, are nonsyndromic).

There are several options for treatment, ranging from removal of the closed suture (suturectomy) to reconstruction of the cranial vault. Each of these options has inherent advantages and disadvantages. Herein we will discuss options for cranial vault reconstruction of the more common nonsyndromic single-suture craniosynostoses (SSCs).

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Anatomy

The types of craniosynostosis may be described in either of the following ways:

  • According to the clinical deformity itself (eg, trigonocephaly)
  • According to the sutures affected (eg, metopic synostosis)

The former descriptive approach was developed by Virchow, who was influenced by then-prevailing anthropologic concepts; the latter was developed by Ingraham and Matson and was based mainly on radiologic evidence of fused sutures. There is considerable correspondence between the two nomenclatures, which is better appreciated in single-suture forms of craniosynostosis.

The rules for growth with regard to the fused sutures are indicated by the arrows in the illustrations below. Closure of a single suture not only causes restriction of growth perpendicular to the fused suture but also causes compensatory growth at adjacent sutures. [2] If the adjacent suture is parallel to the fused suture, the compensatory growth occurs equally in both directions. If the suture is perpendicular to the fused suture, the compensatory growth occurs away from the fused suture.

The following are four common types of craniosynostosis:

  • Trigonocephaly corresponds to metopic synostosis (see the first image below) and is derived from the Greek words trigonos ("triangular") and kephale ("head")
  • Scaphocephaly corresponds to sagittal synostosis (see the second image below) and is derived from the Greek words scaphos ("boat") and kephale
  • Plagiocephaly corresponds to unilateral coronal synostosis (see the third image below) and is derived from the Greek words plagios ("oblique or sloping") and kephale
  • Posterior plagiocephaly corresponds to lambdoid synostosis (see the fourth image below)
Metopic craniosynostosis (trigonocephaly). Metopic craniosynostosis (trigonocephaly).
Sagittal craniosynostosis (scaphocephaly). Sagittal craniosynostosis (scaphocephaly).
Unilateral coronal craniosynostosis (anterior plag Unilateral coronal craniosynostosis (anterior plagiocephaly).
Lambdoid craniosynostosis (posterior plagiocephaly Lambdoid craniosynostosis (posterior plagiocephaly).
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Etiology

The etiology of craniosynostosis is not clear at present, but genetic defects are increasingly being recognized. No inheritance pattern has been identified for nonsyndromic forms of craniosynostosis, though a familial occurrence has been observed in fewer than 10% of the patients. First-degree relatives are affected most commonly in cases of metopic craniosynostosis, followed by sagittal, lambdoid, and, rarely, coronal craniosynostosis. [3]  In familial cases, variable vertical and horizontal penetrance has been observed.

In 2010, a retrospective genetic study of craniosynostosis showed mutations as the cause in 37.5% of bilateral coronal, 17.5% of unilateral coronal, and 11% of multiple-suture synostosis. The mutations were absent in all patients with nonsyndromic metopic, sagittal, and lambdoid craniosynostosis. [4]

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Epidemiology

The overall prevalence of craniosynostosis is estimated as 1 case in 2000 live births. Of the SSCs, the most common, in order of decreasing incidence, are sagittal, unilateral coronal, metopic, and lambdoid synostosis. 

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Prognosis

Surgery improves the cranial deformity in most patients with SSC. However, it is not uncommon to perceive some residual skull-shape abnormality. In a minority of patients, the deformity recurs after a few years and necessitates reoperation. SSC has classically been regarded as a benign entity in terms of neurologic function. The decision to perform surgery was made purely for the purpose of correcting a physical deformity.

Some studies of children who have SSC have suggested that although there does not appear to be an increased incidence of intellectual disability, craniosynostosis may be associated with an increased incidence of subtle learning disabilities. [5, 6]  As many as half of all SSC patients may be found to have neurodevelopmental issues. [4, 7]  Nevertheless, the cause of these subtle learning disabilities has not been elucidated.

Although some may assume that increased intracranial pressure (ICP) plays a role, only a  minority of infants with SSC are found to have increased ICP; yet a higher percentage have learning disabilities  Altered brain morphology has also been proposed as an explanation, but studies have not shown worsened cognitive outcomes in children with more severe deformities. [8]  Advanced imaging (diffusion tensor imaging [DTI]) has also suggested persistent altered brain connectivity in children with treated sagittal craniosynostosis. [9]

Regardless of the timing or type of surgery performed, there is an increased incidence of mild neuropsychological deficits.

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