Craniosynostosis

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DESCRIPTION

Craniosynostosis is defined as partial or complete premature fusion of the cranial sutures. This leads to the distortion of the skull shape, which can cause neurologic, ophthalmic, neurodevelopmental, respiratory, and/or psychological issues when left untreated. This is a heterogenous condition linked to both environmental and genetic factors.

EPIDEMIOLOGY

  • It is estimated to occur in 1 per 2,000 to 2,500 live births.
  • Predisposing factors to craniosynostosis are environmental, genetic, or both.
  • Environmental factors thought to cause craniosynostosis include maternal smoking, in utero exposure to teratogens, intrauterine constraint, maternal thyroid disease, and fetal positioning.
  • Approximately 25% of all craniosynostoses are due to genetic causes.
  • Nonsyndromic craniosynostosis occurs in the remaining 75% of cases.

ETIOLOGY

  • Craniosynostosis can be classified as simple when involving a single suture and complex when involving multiple sutures.
  • Frequencies of the different types of craniosynostoses are:
    • Sagittal (60%)
    • Coronal (25%)
    • Metopic (13–15%)
    • Lambdoid (1–2%)
  • The different nonsyndromic craniosynostoses are described below:
    • Scaphocephaly or dolichocephaly caused by premature fusion of the sagittal suture
    • Anterior plagiocephaly caused by premature fusion of one coronal suture
    • Posterior plagiocephaly caused by premature fusion of one lambdoid suture
    • Trigonocephaly caused by premature fusion of the metopic suture
    • Brachycephaly caused by bicoronal premature fusion
    • Oxycephaly or turricephaly caused by fusion of all or most of the cranial sutures
    • Kleeblattschädel also described as cloverleaf deformity; there is a synostosis of the coronal and lambdoid sutures producing a trilobar shaped-head.

RISK FACTORS

  • White maternal race
  • Advanced maternal age
  • Advanced paternal age
  • Male infant sex
  • Oligohydramnios
  • Maternal smoking
  • Maternal residence in high altitude during antenatal period
  • Paternal occupation (forestry and agriculture, mechanic, repairman)
  • Maternal alcohol use
  • Maternal substance use
  • Maternal use of phenytoin, retinoids, valproate, aminopterin, methotrexate, fluconazole, cyclophosphamide, folic acid, nitrofurantoin, chlordiazepoxide, and chlorpheniramine
  • Fertility treatment
  • Hyperthyroidism in patient
  • Mucopolysaccharidoses

Genetics

  • >60 genes are associated with syndromic craniosynostosis. However, the more common genes are FGFR2, FGFR3, TWIST1, EFNB1, TCF12, and ERF.
  • Majority of the genetic syndromes associated with craniosynostosis have an autosomal dominant inheritance.

PATHOPHYSIOLOGY

  • Craniosynostosis results from premature fusion of one or more cranial sutures, which restricts the growth of the skull perpendicular to the affected suture.
  • Therefore, to accommodate the growing brain, compensatory skull growth occurs parallel to the affected suture.
  • The resulting skull deformity is dependent on the suture affected by this premature closure.

COMMONLY ASSOCIATED CONDITIONS

The different syndromes presenting with craniosynostosis are:

  • Apert syndrome affects the coronal suture.
  • Crouzon syndrome affects the coronal, sagittal, and/or lambdoid sutures.
  • Pfeiffer syndrome affects the bicoronal sutures.
  • Muenke syndrome affects the coronal suture (unilateral or bilateral).
  • Carpenter syndrome affects the coronal, sagittal, and lambdoid sutures.
  • Saethre-Chotzen syndrome affects the coronal, lambdoid, and/or metopic sutures.
  • Jackson-Weiss syndrome affects multiple sutures.
  • Craniofrontonasal syndrome affects the bilateral coronal sutures.

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